Handbook of Engineering and Specialty Thermoplastics: Volume 1: Polyolefins and Styrenics (Wiley-Scrivener)

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Handbook of Engineering and Speciality Thermoplastics

Scrivener Publishing 3 Winter Street, Suite 3 Salem, MA 01970 Scrivener Publishing Collections Editors James E. R. Couper Rafiq Islam Norman Lieberman W. Kent Muhlbauer S. A. Sherif

Richard Erdlac Pradip Khaladkar Peter Martin Andrew Y. C. Nee James G. Speight

Publishers at Scrivener Martin Scrivener ([email protected]) Phillip Carmical ([email protected])

Handbook of Engineering and Speciality Thermoplastics Volume 1 Polyolefins and Styrenics

Johannes Karl Fink Montanuniversität Leoben, Austria

Scrivener

)WILEY

Copyright © 2010 by Scrivener Publishing LLC. All rights reserved. Co-published by John Wiley & Sons, Inc. Hoboken, New Jersey, and Scrivener Publishing LLC, Salem, Massachusetts. Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., I l l River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com. For more information about Scrivener products please visit www.scrivenerpublishing.com. Cover design by Russell Richardson. Library of Congress Cataloging-in-Publication ISBN 978-0-470-62583-5

Printed in the United States of America 10

9 8 7 6 5 4 3 2 1

Data:

Preface This volume on Polyolefins and Styrenics is the first part of a fourpart set on Handbook of Engineering and Specialty Thermoplastics. The other three parts, to be published in late 2010 and 2011, are on Polyethers and Polyesters; Nylons; Water Soluble Polymers. The aim of the Handbook is to keep the practitioner abreast of the recent developments in these subfields as well as to equip the advanced student with up-to-date knowledge as he/she enters the industrial arena. This volume focuses on common types of polymers belonging to the class of polyolefins and styrenics. The text is arranged according to the chemical constitution of polymers and reviews the developments that have taken place in the last decade. A brief introduction to the polymer type is given and previous monographs and reviews dealing with the topic are listed for quick reference. The text continues with monomers, polymerization, fabrication techniques, properties, application, as well as safety issues. Following this information, suppliers and commercial grades are presented. Even though materials are ordered according to chemical structure, a great variety of individual materials belonging to the same polymer type are discussed as well. In particular, the properties and safety data given should be considered as indicative. The reader who is actively engaged with the materials presented here should consult the technical data sheets and the material safety data sheets provided by the individual manufacturers.

How to Use this Book Utmost care has been taken to present reliable data. Because of the vast variety of material presented here, however, the text cannot be complete in all relevant aspects, and it is recommended to the reader to study the original literature for complete information. For v

vi this reason, the author cannot assume responsibility for the completeness and validity of, nor for the consequences of, the use of the material presented here. Every attempt has been made to identify trademarks; however, there were some that the author was unable to locate, and I apologize for any inadvertent omission. Index There are four indices: an index of trademarks, an index of acronyms, an index of chemicals, and a general index. In the index of chemicals, compounds that occur extensively, e.g., "acetone", are not included at every occurrence, but rather when they appear in an important context.

Acknowledgements I am indebted to our university librarians, Dr. Christian Hasenhüttl, Dr. Johann Delanoy, Dolores Knabl, Franz Jurek, Friedrich Scheer, Christian Slamenik, and Renate Tschabuschnig for support in literature acquisition. I also want to express my gratitude to all the scientists who have carefully published their results concerning the topics dealt with here. This book could not have been otherwise compiled. Last, but not least, I want to thank the publisher, Martin Scrivener, for his abiding interest and help in the preparation of the text and Jane Higgins for careful proofreading. Johannes Fink 19th February 2010

Contents Preface 1

v

Metathesis Polymers 1.1 Monomers 1.2 Polymerization and Fabrication 1.2.1 Metathesis Reaction 1.2.2 Catalysts 1.2.3 Rate Controlling 1.2.4 Molecular Weight Regulating Agents 1.2.5 Polymers 1.2.6 Copolymers 1.2.7 Thermosets 1.2.8 Reinforced Polymer Composites 1.2.9 Polymers with Functional Groups 1.2.10 Poly(acetylene)s 1.3 Properties 1.3.1 Mechanical Properties 1.3.2 Optical Properties 1.4 Fabrication Methods 1.5 Fluorinated Polymers 1.6 Special Additives 1.7 Applications 1.7.1 Packaging Films 1.7.2 Wire Coating Materials 1.7.3 Chromatographie Supports 1.8 Suppliers and Commercial Grades 1.9 Safety References vu

1 2 2 3 7 14 17 17 18 19 21 23 25 26 26 26 27 27 28 29 29 29 30 32 35 35

viii 2

Engineering Thermoplastics: Polyolefins and Styrenics Cyclic Olefin Copolymers 2.1 Monomers 2.2 Polymerization and Fabrication 2.2.1 Catalysts 2.2.2 Metallocene Catalyzed Polymerization . . . . 2.2.3 Addition Polymerization 2.2.4 Thermosetting Resins 2.2.5 Analysis 2.2.6 Solvent Bonding 2.3 Properties 2.3.1 Mechanical Properties 2.3.2 Thermal Properties 2.3.3 Optical Properties 2.3.4 Barrier Properties 2.3.5 Chemical Resistance 2.4 Applications 2.4.1 Films 2.4.2 Optical Applications 2.4.3 Medical Applications 2.4.4 Packaging Areas 2.4.5 Absorption of Organic Contaminants 2.4.6 Adhesives in Semiconductor Technology . . . 2.5 Suppliers and Commercial Grades 2.6 Safety 2.7 Environmental Impact and Recycling References

3 Ultra High Molecular Weight Poly(ethylene) 3.1 Monomers 3.2 Polymerization and Fabrication 3.2.1 Ziegler-Natta Catalysts 3.2.2 Mixed Catalysts 3.2.3 Single-Site Catalysts 3.2.4 Fractionation 3.2.5 Crosslinking 3.2.6 Fabrication 3.2.7 Porous Parts 3.3 Properties

41 41 43 45 47 48 50 51 51 52 52 52 52 52 53 53 53 54 58 59 62 63 65 65 67 67 75 75 76 76 78 79 80 81 81 82 82

Contents

4

ix

3.3.1 Mechanical Properties 3.3.2 Electrical Properties 3.3.3 Optical Properties 3.3.4 Other Properties 3.4 Special Additives 3.5 Applications 3.5.1 Prosthetic Joints 3.5.2 Microporous Membranes 3.5.3 Binders for Filter Materials 3.5.4 Fibers 3.6 Suppliers and Commercial Grades 3.7 Safety References

83 83 83 83 83 84 84 96 99 99 100 100 104

Poly(methyl)pentene 4.1 Monomers 4.2 Polymerization and Fabrication 4.2.1 Ziegler-Natta Polymerization 4.2.2 Metallocene Catalyzed Polymerization 4.2.3 Living Polymerization 4.2.4 Modification 4.2.5 Flash Spinning 4.3 Properties 4.3.1 Mechanical Properties 4.3.2 Thermal Properties 4.3.3 Electrical Properties 4.3.4 Optical Properties 4.3.5 Other Properties 4.4 Applications 4.4.1 Membranes 4.4.2 Heat Sealable Compositions 4.4.3 Laminates for Packaging Films 4.4.4 Overwrap Films 4.4.5 Image Forming Solution 4.4.6 Xerographic Devices 4.4.7 Acoustic Devices 4.4.8 Miscellaneous 4.5 Suppliers and Commercial Grades

109 109 Ill Ill 112 114 114 116 118 118 118 119 119 119 120 120 123 124 125 126 127 128 129 132

....

x

Engineering Thermoplastics: Polyolefins and Styrenics References

133

5

Ionomers 5.1 Monomers 5.2 Polymerization and Fabrication 5.2.1 Processing 5.2.2 High Acid Types 5.2.3 Mechanisms of Crosslinking 5.3 Properties 5.3.1 Mechanical Properties 5.3.2 Thermal Properties 5.3.3 Electrical Properties 5.4 Special Additives 5.4.1 Antistatic Agents 5.5 Applications 5.5.1 Fuel Cell Anodes 5.5.2 Solar Control Laminates 5.5.3 Heat Seal Modifiers 5.6 Suppliers and Commercial Grades References

137 137 138 139 139 140 143 143 144 144 144 144 145 145 145 146 146 148

6

Poly(isobutylene) 6.1 Monomers 6.2 Polymerization and Fabrication 6.2.1 Catalyst Systems 6.2.2 Polymerization Techniques 6.2.3 Poly(isobutylene) Grades 6.2.4 Star Shaped Polymers 6.2.5 Grignard Synthesis 6.2.6 End Group Functionalization 6.2.7 Blends and Composites 6.2.8 Halogenation Processes 6.3 Properties 6.3.1 Mechanical Properties 6.3.2 Thermal Properties 6.3.3 Electrical Properties 6.3.4 Optical Properties 6.3.5 Gas Permeation 6.3.6 Chemical and Physical Resistance

151 151 152 154 154 154 155 156 157 158 161 161 162 163 164 165 165 166

Contents

χι

6.4 6.5

Special Additives Applications 6.5.1 Drag Reduction Additives 6.5.2 Oil and Fuel Additives 6.5.3 Polymeric Antioxidants 6.5.4 Emulsifiers 6.5.5 Chewing Gums 6.5.6 Medical Applications 6.5.7 Pressure Sensitive Adhesives 6.6 Suppliers and Commercial Grades 6.7 Environmental Impact and Recycling References

166 166 167 167 170 173 174 175 176 177 179 179

7

Ethylene Vinyl Acetate Copolymers 7.1 Monomers 7.1.1 Vinyl Acetate 7.2 Polymerization and Fabrication 7.2.1 Radical Solution Polymerization 7.2.2 Aqueous Emulsions 7.2.3 Saponification 7.2.4 Foaming 7.3 Properties 7.3.1 Mechanical Properties 7.3.2 Optical Properties 7.4 Applications 7.4.1 Blends 7.4.2 Heat Seal Applications 7.4.3 Sealing 7.4.4 Waxes 7.4.5 Hot Melt Adhesives 7.4.6 Cold Flow Improvers 7.4.7 Drug Delivery 7.5 Suppliers and Commercial Grades References

187 187 189 190 190 192 195 196 197 197 197 197 197 198 199 201 202 202 204 204 206

8

Acrylonitrile-Butadiene-Styrene Polymers 8.1 Monomers 8.1.1 Rubbers 8.2 Polymerization and Fabrication

211 211 213 215

xii

Engineering Thermoplastics: Polyolefins and Styrenics 8.2.1 Mass Polymerization 215 8.2.2 Emulsion Polymerization 218 8.2.3 Low Gloss Types 221 8.2.4 Blends 221 8.3 Properties 227 8.3.1 Mechanical Properties 227 8.3.2 Thermal Properties 228 8.3.3 Electrical Properties 229 8.3.4 Optical Properties 230 8.3.5 Surface Properties 231 8.4 Special Additives 231 8.4.1 Heat Stabilizers 232 8.4.2 Flame Retardants 232 8.4.3 Combined UV Stabilizer and Flame Retardant 234 8.4.4 Fillers 235 8.5 Applications 236 8.5.1 Foam Stops 236 8.5.2 Electroconductive Resins 236 8.5.3 Tunable Magneto Rheological Compositions . 237 8.5.4 Cement Additive 237 8.5.5 Membrane Materials 238 8.5.6 Electroless Plating 240 8.5.7 Encapsulation Shells for Phase Change Materials241 8.5.8 Hydrogen Storage 242 8.5.9 Carbon Materials 243 8.6 Suppliers and Commercial Grades 244 8.7 Safety 244 8.8 Environmental Impact and Recycling 247 8.8.1 Material Recycling 247 8.8.2 Pyrolysis 252 References 256

9 High Impact Poly(styrene) 9.1 Monomers 9.1.1 Impact Modifiers 9.2 Polymerization and Fabrication 9.2.1 Continuous Radical Polymerization 9.2.2 Rubbers

269 269 269 270 271 272

Contents 9.2.3 Nanocomposites 9.3 Properties 9.3.1 Mechanical Properties 9.3.2 Thermal Properties 9.3.3 Particle Size 9.4 Special Additives 9.4.1 Flame Retardants 9.5 Applications 9.5.1 Foodservice Applications 9.5.2 Refrigerator Cabinets 9.5.3 Antistatic Compositions 9.6 Suppliers and Commercial Grades 9.7 Safety 9.7.1 Emissions from Processing 9.7.2 Emissions from Recycled Products 9.7.3 Accumulation in Food from Packaging . . . . 9.8 Environmental Impact and Recycling 9.8.1 Material Recycling 9.8.2 Feedstock Recycling References 10 Styrene/Acrylonitrile Polymers 10.1 Monomers 10.2 Polymerization and Fabrication 10.2.1 Emulsion Polymerization 10.2.2 Intermediate Polymerization 10.2.3 Solution and Bulk Polymerization 10.2.4 Expandable Microspheres 10.2.5 Modification 10.2.6 Interfering Reactions 10.3 Properties 10.3.1 Mechanical Properties 10.3.2 Thermal Properties 10.3.3 Electrical Properties 10.3.4 Optical Properties 10.3.5 Chemical Resistance 10.4 Special Additives 10.5 Applications

xiii 274 275 276 276 276 278 278 279 279 281 282 283 283 283 286 287 288 288 291 292 297 297 297 298 298 298 300 300 302 302 303 303 304 304 305 306 306

xiv

Engineering Thermoplastics: Polyolefins and Styrenics 10.5.1 Blends 10.5.2 Expandable Resins 10.5.3 Low Gloss Additives 10.5.4 Laser-inscribed Moldings 10.6 Suppliers and Commercial Grades 10.7 Environmental Impact and Recycling References

306 308 308 309 310 310 312

11 Methyl methacrylate/Butadiene/Styrene Polymers 11.1 Monomers 11.2 Polymerization and Fabrication 11.2.1 Basic Method for Preparation 11.2.2 Varied Methods 11.3 Properties 11.3.1 Thermal Properties 11.3.2 Optical Properties 11.4 Special Additives 11.5 Applications 11.5.1 Medical Applications 11.5.2 Impact Modifiers 11.5.3 Thermoforming Applications 11.5.4 Aqueous Additive Systems 11.5.5 Prepregs 11.5.6 Powder Coatings 11.6 Suppliers and Commercial Grades References

315 315 316 316 318 318 319 319 319 320 320 320 321 321 322 324 324 328

12 Acrylonitrile/Styrene/Acrylate Polymers 12.1 Monomers 12.2 Polymerization and Fabrication 12.2.1 Two Stage Preparation for Structured Latexes 12.2.2 Three Stage Preparation 12.2.3 Blends 12.3 Properties 12.3.1 Mechanical Properties 12.3.2 Optical Properties 12.3.3 Chemical Properties 12.4 Special Additives 12.4.1 Weatherability Improvers

331 331 332 333 334 335 336 337 338 338 338 339

Contents 12.4.2 Gloss Reducers 12.4.3 Heat Distortion Improving Agents 12.5 Applications 12.5.1 Multilayer Laminates 12.5.2 Roofing Material 12.5.3 Antimicrobial Acrylonitrile-styrene-acrylate 12.6 Suppliers and Commercial Grades References Index Tradenames Acronyms Chemicals General Index

xv 339 340 341 342 342 . 343 343 345 349 349 361 364 375

This Page Intentionally Left Blank

1 Metathesis Polymers Polymers using the ring opening metathesis polymerization (ROMP) technique were first obtained at 1960 by Eleuterio (1,2). The patents deal with the polymerization of bicyclo[2.2.1]heptene-2, i.e., norbornene using a molybdenum catalyst dispersed on alumina. The polymer was found to contain double bonds in trans and cisconfiguration in considerable amounts. The mechanism of polymerization has been described as shown in Figure 1.1. Metal-catalyzed olefin metathesis had an enormous impact on organic synthesis in general. Extensive research on mechanistic aspects (3,4) and the development of catalysts has been performed, which culminated in the award of the Nobel Prize for Chemistry in 2005 to Chauvin, Grubbs and Schrock.

G

-

Figure 1.1: Metathesis Polymerization of Norbornene and Cyclopentene 1

2

Engineering Thermoplastics: Polyolefins and Styrenics Table 1.1: Monomers for Metathesis Polymerization Monomers

References

Cyclopentene 1,5-Cyclooctadiene Norbornene l,4-Dihydro-l,4-methanonaphthalene Norbornene 2-ethylhexyl carboxylate Norbornene isobornyl carboxylate Norbornene phenoxyethyl carboxylate Dodecylenedinorbornene dicarboxyimide exo,e;ro-N,N'-Propylene-di-(norbomene-5,6-dicarboxyimide 8-Methyltetracyclo[4.4.0.12.8.17.10]dodeca-3-ene Dicyclopentadiene

1.1

(1/2) (5) (5) (5) (5) (5) (6) (6)

Monomers

Cyclopentene is readily available as a byproduct in the ethylene production. Norbornene 2-ethylhexyl carboxylate is obtained by the Diels-Alder reaction of 2-ethylhexyl acrylate with cyclopentadiene (5). Norbornene isobornyl carboxylate, norbornene phenoxyethyl carboxylate, and other related monomers are synthesized according to the same route. Polymers obtained from these esters exhibit excellent properties in terms of controlling the crosslinking density, the associated product modulus, and the glass transition temperature (Tg), thus allowing tailoring the properties of elastomers, plastics and composites. Other suitable monomers are summarized in Table 1.1 and sketched in Figure 1.2.

1.2

Polymerization and Fabrication

The monomers dealt with can be polymerized by various mechanisms, not only by ROMP. For example, a rapid polymerization of norbornadiene occurs using a homogeneous catalytic system consisting of nickel acetylacetonate or a nickel-phosphine complex, such as nickel bis-(tri-n-butylphosphine) dichloride (NiCl2(TBP)2) or nickel bis-(tricyclohexylphosphine) dichloride (NiCl2(TBP)2). Nickel acetylacetonate as catalyst is known to initiate rather a classical vinyl polymerization (7). The classical vinyl polymerization

Metathesis Polymers

O ch

Cyclopentene

Norbornene

*^®

1,4-Dihydro-1,4-melhanonaphthalene

3

Dicyclopentadiene

O

1,5-Cyclooctadiene

Figure 1.2: Monomers used for Metathesis Polymers

Figure 1.3: Difference Between Vinyl Polymerization and Ring Opening Metathesis Polymerization (7) of cyclic monomer deserves much less attention in the literature, nevertheless there is a big variety of catalysts described (7). By the way, the intended use of this polymer is as a solid high energy fuel (8). The difference between ordinary vinyl polymerization and ring opening metathesis polymerization is shown in Figure 1.3. 1.2.1 Metathesis

Reaction

The metathesis reaction consists of a movement of double bonds between different molecules, as shown in Figure 1.4. Thus, the metathesis reaction can be addressed as a transalkylideneation reaction. The cleavage of the carbon-carbon double bonds was established using isotopic labelled compounds that were subjected to ozonolysis after reaction (9). Clearly, if the radicals R\ and R4 are connected via a carbon chain, a longer chain will be formed, resulting consecutively in the for-

4

Engineering Thermoplastics: Polyolefins and Styrenics

R

4\

R3

C=C

ßl

R2

R4V

R3

ßl

C C

R2

Figure 1.4: Scheme of Metathesis Reaction Table 1.2: Types of Metathesis Reactions (10) Term

Acronym

Ring opening metatheses polymerization Living ring opening metatheses polymerization Ring closing metathesis Acyclic diene metathesis polymerization Ring opening metathesis Cross-metathesis

ROMP LROMP (11,12) RCM ADMET ROM CM or XMET

mation of macromolecular structures. For this reason, this type of polymerization is also called ring opening polymerization. The polymeric structures contain double bonds in the main chain. This allows classical vulcanization processes with sulphur. Since the reaction is reversible, the metathesis process has been used to synthesize degradable polymers with vinyl groups in the backbone. In this way, the structure of crosslinked rubbers has been elucidated. The mechanism of metathesis is used in several variants, either to polymerize, degrade, etc. The various reaction types are summarized in Table 1.2. The metathesis reaction is catalyzed by metalcarbene complexes. The mechanism, exemplified with cyclopentene is shown in Figure 1.5. In the first step, the complex reacts with a monomer to regenerate the carbon metal double bond. This double bond is able to react further with another monomer thus increasing the size of the molecule. If the metathesis polymerization is performed in solution, the preferred solvents are méthylène chloride or chlorobenzene. Preferably, the solvent is aprotic in order to avoid ionic side reactions. The molecular weight is controlled by the addition of an acyclic olefin, such as 1-butene (13). The polymerization reaction can be quenched by the addition of alcohols, amines or carboxylic acids, such as ethanol, ferf-butyl

Metathesis Polymers

OH3 H

H3C-¿

¿

OC I vCO CO

CHQ

^\

^ H3C-¿

H

5

¿=^Λ

^V\f OC'I v CO CO

Figure 1.5: Initial Steps of the Metathesis Polymerization phenol, diethylamine, acetic acid. The polymerization reaction is an equilibrium reaction. The relevant equilibria are 1. 2. 3. 4.

Monomer-polymer equilibrium, in more general sense, Equilibrium between polymers of different chain length, Ring-chain equilibrium, and C/s-frans-equilibrium.

The free enthalpy of polymerization (AGp) is sufficiently negative for rings of a size of 3, 4, 8, and larger to have the equilibrium on the side of the polymer. However, for rings of a size of 5, 6, and 7 - because of the low ring tension - the free enthalpy of polymerization can be even positive. For example, AGa,p for the formation of the c/s-polymer of cyclohexene, AGo,p = +6.2 kjmol" 1 and for frans-polymer of cyclohexene, AGo,p = +7.3 kj mol" 1 (14). However, at cryogenic temperatures, AGp decreases and oligomers can be formed. The polymer contains a fraction of high molecular linear chains and a cyclic oligomeric fraction. If initially the monomer concentration is below the equilibrium value for a linear polymer, essentially no polymer is formed, but only cyclic oligomers. At higher concentration, both a linear polymer and a cyclic oligomer is formed. The ratio of the amounts of c/s-linkages to irans-linkages depends on the nature of the catalyst. A tungsten or molybdenum catalyst, respectively, can be prepared by heating tungsten trioxide with phosphorus pentachloride in o-dichlorobenzene up to 120°C under vigorous stirring. The solution changes from colorless to deep red and a considerable amount of precipitate is left behind at the bottom of the reaction vessel. The soluble chloride is used for the further steps.

6

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Table 1.3: M o n o m e r s for R O M P Polymerization (15) Monomer

Rate 3

f]b

Cyclopentene c Bicyclo[2.2.1]heptene-2c 5-Cyano-5-methyl-bicyclo[2.2.1]heptene-2 3,6-Methylene-l,2,3,6-tetrahydro-ris-phthalic anhydride 2,3-Diethoxycarbonyl-bicyclo[2.2.1]hepta-2,5-diene 1,5-Cyclooctadienec N-Phenyl-3,6-methylene-l,2,3,6-tetrahydro-ds-phthalimide N-Butyl-3,6-methylene-l,2,3,6-tetrahydro-cz'sphthalimide 5,6-Dimethoxycarbonyl-bicyclo[2.2.1]heptene-2 5-(4-Quinolyl)-bicyclo[2.2.1]heptene-2 5-Acetoxy-bicyclo[2.2.1 ]heptene-2 5-Methoxymethylbicyclo[2.2.1]heptene-2 A/,N-Diethyl-bicyclo[2.2.1 ]heptene-2-carbonamide l,4-Dihydro-l,4-methanonaphthalene 5-Chloromethyl-bicyclo[2.2.1 ]heptene-2 5-(2-Pyridyl)-bicyclo[2.2.1]heptene-2 5,5-Dichloro-bicyclo[2.2.1 ]heptene-2 a Rate of polymerization/ [g g _ 1 h _ 1 ] at 70°C except for with superscript c b Viscosity/ [dig - 1 ] c Polymerized at 30°C d Solvent: 1,2-dichloroethane e Solvent: N,JV-dimethylformamide

1,590 1,365 1,365

2.05d 1.88d 1.22e

1,283 1,264 1,202

0.97e 1.17e 1.98d

1,182

1.05d

1,121 1.07e 1,039 0.70e 998 0.81e 978 0.85e 978 0.69e 937 0.94e 897 0.78d 876 0.80d 876 0.81 e 815 l . l l d monomers

The actual polymerization takes place in an autoclave under inert atmosphere, where the supernatant liquid of the foregoing step is placed with the dried and rectified monomer and the second catalyst compound, namely diethylaluminum chloride in 1,2-dichloroethane solution (15). The polymerization is conducted at 70°C for 60 min while stirring well. According to this recipe, a series of cyclic monomers can be polymerized. Examples are shown in Table 1.3. Macromonomers provide an easy access to a large number of functional copolymers and controlled topologies, such as comb-like, star-like, bottle brush, and graft copolymers. These types exhibit exceptional solution or solid state properties compared to their linear homologues.

Metathesis Polymers

7

Initially, the polymerization of macromonomers was achieved by free radical polymerization reactions, which allowed only a limited control of the final properties. With the advent of ROMP and new free radical polymerization techniques, such as atom transfer radical polymerization (ATRP) the control of final properties became more facile (16). ATRP and ROMP techniques can be combined for the synthesis of macroinitiators (17). Macromonomers with norbornene end groups were synthesized by living anionic polymerization. The norbornene groups were polymerized by molybdenum catalysts. A series of other ω-norbornenyl macromonomers were synthesized and polymerized by metathesis polymerization. 1.2.1.1 Living Ring Opening Metathesis Polymerization Living ring opening metathesis polymerization is a special kind of ROMP. In order to approach the conditions of a living polymerization reaction, the following requirements must be fulfilled (12): 1. Fast and complete initiation, 2. Linear relationship between the degree of polymerization and conversion, and 3. Polydispersity less than 1.5. Thus, the catalyst must have certain special properties, to be regarded as a living ROMP catalyst. 1.2.2

Catalysts

Numerous catalyst systems have been developed. Most common catalysts are based on tungsten of molybdenum. Transition metals ranging from group IV to group VIII have been found to be suitable. The catalysts are commonly classified as given in Table 1.4. The half-life times of the polymerization reaction can be adjusted from a few seconds to several days. Typical for such catalysts is the metalcarbene bond, as shown in Figure 1.5. In varieties of the catalytic principle of the metalcarbene bond, this bond is not initially present, but may be formed by a co-catalyst or by some reactions with the monomer itself.

8

Engineering Thermoplastics: Polyolefins and Styrenics Table 1.4: Classification of Catalysts (18) Catalyst Type Initiators with metal alkyl co-catalysts Initiators with alkylidene or metallacyclobutanes of early transition metals Group VIII initiators without metal alkyl co-catalysts Group VIII alkylidenes Table 1.5: Monomer Catalyst Systems (14) Monomer

Catalyst

Cyclopentene WCl6/(CH2=CHCH2)4Si Cyclopentene WC16/CH3-CH2A1C12 CIMXHs C6H5C=W(CO)4Br a Temperature of polymerization b Property of polymer

T /°C a

Property1"

-10 +20

high eis high trans M„ = 5.9 k Dalton

Examples for catalysts are listed Table 1.5 and shown in Figure 1.6. For the metathesis polymerization of acetylene related compounds, catalysts with a metal carbyne bond have been introduced, such as C 6 H 5 C = W(CO)4Br. Molybdenum-based catalysts are highly active initiators, however, monomers with functionalities with acid hydrogen, such as alcohols, acids, or thiols jeopardize the activity. In contrast, ruthenium-based systems exhibit a higher stability towards these functionalities (19). An example for a molybdenum-based catalyst is (20) MoOCl2(t-BuO)2, where t-BuO is the terf-butyl oxide radical. The complex can be prepared by reacting M0OCI4 with potassium tertbutoxide, i.e., the potassium salt of ierf-butanol. Ruthenium and osmium carbene complexes possess metal centers that are formally in the +2 oxidation state, have an electron count of 16 and are penta-coordinated. Ruthenium complexes exhibit a higher catalytic activity when an imidazole carbene ligand is coordinated to the ruthenium metal center (21). The polymerization of cyclooctene shows a pronounced dependence of the N-heterocyclic carbene ligand, due to steric effects.

Metathesis Polymers

R—N α

9

N—R

P(Cy)3 'RU=

CKI

(II) /

OH3

'~'3*-

C/H3

'~'3^-/

Ck Ru=

.Ph

CKl

PBu 3

(III)

Figure 1.6: Metathesis Catalysts (22): Phenylmethylene-bis-(tricyclohexylphosphine) ruthenium dichloride (I), (IMesH2)(PCy3)(Cl)2Ru=CHPh (III) These ruthenium complexes are also active catalysts for ring-closing metathesis reactions in high yields. Ruthenium catalysts, coordinated with an N-heterocyclic carbene allowed for the ROMP of low-strain cyclopentene and substituted cyclopentenes (10,23). Suitable ruthenium and osmium carbene compounds may be synthesized using diazo compounds, by neutral electron donor ligand exchange, by cross metathesis, using acetylene, cumulated olefins, and in an one-pot method using diazo compounds and neutral electron donors (24). The route via diazo compounds is shown in Figure 1.7. Since the ruthenium and osmium carbene compounds of the type shown in Figure 1.7 are stable in the presence of a variety of functional groups, the olefins involved in the polymerization reactions may optionally be substituted with various functional groups. The synthesis of a ruthenium catalyst in a one step procedure is shown in Figure 1.8. A dimer complex of cymene, i.e., 4-isopropyltoluene) and RuCl2 is reacted under inert atmosphere with tricyclohexylphosphine and 3,3-diphenylcyclopropene in benzene

10

Engineering Thermoplastics: Polyolefins and Styrenics

PPh3

M

^Ru—PPh33 + A CK^l R--K,, H PPh, H '3

PPh3 H ►-

^ R u = CN CKl R pph 3 H

Figure 1.7: Synthesis of Ruthenium Carbene Compounds via Diazo Compounds (24)

solution under reflux at 83-85°C for 6 h (25). The catalyst Cl 2 Ru(PCy 3 ) 2 (=CHCH=CPh 2 ), cf., Figure 1.8, is obtained in a yield of 88%. In the same way, catalysts, where the metal atom is in a ring, can be synthesized. This type of catalysts is suitable for the synthesis of cyclic polymers (26). The synthesis route is shown in Figure 1.9. The preparation of the catalyst starts with the synthesis of 1-mesityl-3-(7-octene)-imidazole bromide. This compound is prepared by condensing mesityl imidazole with 8-bromooctene. The resulting salt is deprotonated with (TMS)2NK, where TMS is the tetramethylsilyl radical. This step is performed in tetrahydrofuran at -30°C for 30 min. To this product a solution of the ruthenium complex (PCy 3 ) 2 Cl 2 Ru=CHPh is added at 0°C. Bringing the solution slowly to room temperature, after 1 h the ligand displacement was determined to be complete. Afterwards, the reaction mixture is then diluted with n-pentane and heated to reflux for 2 h to induce intramolecular cyclization. The ruthenium catalyst can be used to catalyze the synthesis of a cyclic poly(octenamer). The catalyst is added to cis-cyclooctene in CH2CI2 solution at 45° C. The intermediate macrocyclic complex undergoes an intramolecular chain transfer to yield the cyclic polymer and regenerate the catalyst. In this way, cyclic polymers with number-average molecular weights M„ up to 1200 k Dal ton can be prepared by varying the ration of catalyst to monomer or the initial monomer concentration. However, with initial monomer concentrations of less than 0.2 m o l l - 1 , only low molecular weight cyclic oligomers are obtained. The polydispersity index Mw/Mn of the resulting polymers is approximately 2. In the case of cycloolefin monomers with a strained double bond,

Metathesis Polymers

CI—Ru Cl( "CI Ru-CI

+

Figure 1.8: Synthesis of a Ruthenium Catalyst (25)

11

12

Engineering Thermoplastics: Polyolefins and Styrenics

+

pzKJ ^ N

'

N ^__^

x'i

Figure 1.9: Catalyst for Macrocyclic Polymers such as norbornene, the ring opened product is thermodynamically favored. Therefore, it is not necessary for the catalyst to bear a metalcarbene moiety in its structure to initiate the ROMP. Any complex capable of initiating metalcarbene formation in situ should perform equally well as a catalyst for the ROMP. For instance, it is well known that RuC^ x 3H2O can accomplish the ROMP of norbornene quite effortlessly, even though there is no carbene present in the catalyst. It is suspected that the reaction involves as a first step, when the metal halide reacts with the monomer, the formation of a metalcarbene moiety that is responsible for the subsequent propagation reaction (20). Hydrates of RUCI3, IrCl3, and OsCb are suitable catalysts for the ROMP of norbornene in aqueous and alcoholic solvents. Ruthenium trichloride hydrate is used for the industrial production of poly(norbornene). These hydrates act for the ROMP of norbornene and norbornene derivatives in pure water through an emulsion process (18). Olefin metathesis catalysts based on ruthenium have been shown to exhibit a quite good tolerance to a variety of functional groups. The ring opening metathesis polymerization of strained, cyclic olefins initiated by group VIII salts and coordination complexes in aque-

Metathesis Polymers

13

ous medium has been described. Although these complexes serve as robust polymerization catalysts in water, the polymerization is not of living type. Moreover, inefficient initiation steps produce erratic results, in particular, when less than 1% of the metal centers are converted to catalytically active species. This results in poor control over polymer molecular weight (27). In contrast, in living polymerization systems, the polymerization occurs without chain transfer or chain termination, giving greater control over polydispersity of the resultant polymers. Such polymerization systems allow the controlled synthesis of water-soluble polymers and enable precise control over the composition of block copolymers. Water-soluble, aliphatic phosphines have been synthesized for their inclusion into ruthenium olefin metathesis catalysts (28). Complexes of the type Rua 2 (=CHPh)(Cy2P(N,N-dimethylpiperidiniumchloride)) 2 and RuCl2(=CHPh)(Cy2PCH2CH2N(CH3)+Cl)2 can be activated in water with a strong Bronsted acid. In the presence of a Bronsted acid, the complexes quickly and quantitatively initiate the living polymerization of water-soluble monomers without the need of a surfactant or of organic solvents (27). This finding is a significant improvement over aqueous ROMP systems using aqueous ROMP catalysts. The propagating species in these reactions is stable. The synthesis of water-soluble block copolymers can be achieved via sequential monomer addition. The polymerization is not of living type in the absence of acid. In addition to eliminating hydroxide ions, which would cause catalyst decomposition, the catalyst activity is also enhanced by the protonation of the phosphine ligands. Remarkably, the acids do not react with the ruthenium alkylidene bond. Although the alkylidene complexes initiate the ROMP of functionalized norbornenes and 7-oxanorbornenes in aqueous solution quickly and completely in the absence of acid, the propagating species in these reactions often decompose before the polymerization reaction is complete. For example, in the ROMP of the water-soluble

14

Engineering Thermoplastics: Polyolefins and Styrenics

monomer exo-N-(N',Ν',Ν'-trimethylammonio) ethyl-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide chloride and also exo-N-(N',N',N'trimethylammonio)ethyl-bicyclo-7-oxabicyclo[2.2.1]hept-5-ene-2,3dicarboximide chloride, conversions ranging from 45-80% are observed. Although the water-soluble complexes are similar to ruthenium alkylidenes, which are very stable toward polar and protic functional groups in organic solvents, they appear to be susceptible to termination reactions, when dissolved in water or methanol (27).

2.2.3 Rate

Controlling

The rate of polymerization can be controlled by a gel modification additive. A gel modification additive is a substance that cooperates with the catalyst to change the rate of the catalyzed reaction. Most generally, a gel modification additive may be any electron donor or Lewis base. Particularity suitable compounds acting in this way are tricyclohexylphosphine, tricyclopentylphosphine, triisopropylphosphine, triphenyl phosphine, and pyridine. Triphenyl phosphine is an example of a gel modification additive that acts to retard the rate of reaction, when the catalyst has tricycloalkylphosphine ligands. The catalyst with tricycloalkylphosphines ligands is much more active in ROMP than when the ligands would be triphenyl phosphines. The action of triphenyl phosphine on the catalyst is explained that the added triphenyl phosphine substitutes the tricycloalkylphosphine ligands in the coordination sphere of the complex and decreases the activity of the catalyst. Thus, in general, a gel modification additive decreases the rate of reaction if the catalyst becomes less active by an exchange reaction of the respective ligands. Since monomer coordination is required for polymerization, the gel modification additive can also slow the polymerization reaction by competing with the monomer for coordination sites on the metal center. A general rule for the case discussed above, increasing the concentration of the gel modification additive will decrease the rate of polymerization reaction. On the other hand, if the pot life is too long, in the case of a catalyst with triphenyl phosphine ligands, the pot

Metathesis Polymers

15

life can be decreased by adding an other type of gel modification additive, such as tricyclohexylphosphine or tricyclopentylphosphine. In this case, it is believed that the tricycloalkylphosphine gel modification additive exchanges with the triphenyl phosphine ligands leading to a more active catalyst. The situation is reverse from the case discussed before. However, even when the catalyst becomes more active, as the concentration of gel modification additive is increased, the additive will compete with the monomer for coordination sites on the metal center and the additive may eventually act to decrease the rate of reaction. There must be sufficient time for the ligands and the gel modification additive to totally equilibrate between being bound by the catalyst and being in solution in the monomer. In some cases, to obtain the maximum effect of a gel modification additive, it may be necessary to allow the gel modification additive and the catalyst complex to equilibrate in a non reactive solvent before the monomer is added. This is particularly important where exchange of the ligands and gel modification additive appears to be slow relative to the onset of polymerization, such as cases where a very bulky gel modification additive, such as tricyclohexylphosphine is being exchanged on the catalyst complex. Experiments concerning the polymerization of dicyclopentadiene show the effects that are qualitatively discussed before. The type of ruthenium catalysts, as shown in Figure 1.8, however with cyclopentadienyl ligands instead of cyclohexyl ligands, P(CyPentyl) 3 Cl 2 Ru(=CHCH=CPh 2 ) are added to dicyclopentadiene and an amount of gel modification additive is added and mixed. The mixture is then poured in a mold and is allowed to polymerize. In the experiments, the gel time is defined as 1. The time at which a stir bar ceases turning in a 250 ml flask during mixing of the catalyst and monomer, or 2. The time at which a glass pipet lowered or pushed into a very high viscosity poured sample will no longer pick up or have cling to the pipet any of the polymerizing sample.

16

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Table 1.6: Gel Modification Additives vs. Gel Time (25) Catalyst: 0.85 g g - 1 Monomer Mold Resin Gel Time Peak Exotherm min °C °C min °C Additive a Amount b 1 1 1 2 2 3 4 5 6 7 7 8 8 9 10 11 2 2 1 none 2

0.15 0.43 1.14 1.07 2.34 1.31 0.95 0.71 0.96 1.03 2.34 0.96 4.53 2.34 2.34 2.34 0.31 0.84 0.50 0.00 0.81

mg mg mg mg mg mg mg mg mg mg mg mg mg μ\ μ\ μ\ mg mg mg mg mg

36.4 36.2 36.3 38.6 36.3 35.9 37.1 36.6 35.0 33.1 33.0 34.0 35.0 35.6 33.9 33.6 39.2 37.5 39.3 40.6 38.3

31.0 31.0 31.0 33.3 33.2 32.5 31.0 32.0 31.0 32.0 32.0 32.0 32.0 32.0 32.0 32.0 33.6 32.0 32.0 34.0 32.0

6.00 9.00 21.00 6.00 11.00

7.33 10.83 38.30 7.20 13.75

160.3 173.2 91.5 190.4 184.9

10.00

15.10

145.1

4.03

148.4

oo

oo oo

1.50 2.50 1.50 2.75 1.23 1.88 1.32 9.00 12.00 >16.00 >60.0 13.00

oo

oo oo c c

oo oo oo c C

-

-

c

c

15.00 21.00 14.00 20.75

44.2 48.00 14.00 111.7

c c

c c

a

b c

Gel Modification Additives 1 Tricyclopentylphosphine 3 Triphenyl phosphite 5 Propylamine 7 Benzonitrile 9 Anhydrous Acetonitrile 11 Furan Amount additive mg g _ 1 or μ\ g Too fast to measure

2 4 6 8 10

Tricyclohexylphosphine Py rid ine Tributylphosphine Triphenylarsine Thiophene

monomer

Metathesis Polymers

17

The results of the polymerization experiments are shown in Table 1.6. Besides the facts discussed, it can be seen that triphenyl phosphite, propylamine, and tributylphosphine effectively inhibit the polymerization reaction. In contrast, benzonitrile, triphenylarsine, anhydrous acetonitrile, thiophene, and furan accelerate the reaction (25). 1.2.4 Molecular Weight Regulating

Agents

The regulation of the molecular weight of the ring opening polymer can be achieved through controlling the polymerization temperature, the type of catalyst, the type of solvent, and by adding a molecular weight regulating agent to the reaction system. Examples of suitable molecular weight regulating agents include α-olefins, such as ethylene, propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1octene, 1-nonene, and 1-decene, as well as styrene. 1-Butene and 1-hexene are particularly preferred (29). The molecular weight regulating agent may utilize a single compound, or a mixture of two or more different regulating agents. The amount of the molecular weight regulating agent used is typically from 0.02 to 0.5 mol per mol of monomer. 1.2.5

Polymers

In general, ring opening polymers can be roughly classified into thermoplastic ring opening polymers and curing type ring opening polymers. The curing type ring opening polymers are obtained by bulk ring opening polymerization reaction using polymerization catalysts of relatively high activity, such as tungsten-based ring opening polymerization catalysts or molybdenum-based ring opening polymerization catalysts. The curing type ring opening polymers are used for making molded products by reactive injection molding (RIM) method. In case of producing curing type ring opening polymers, generally, a reaction mixture containing the monomer and the ring opening polymerization catalyst is injected into a mold to carry out bulk ring opening polymerization. Molded products can be obtained without employing melt molding methods, such as injection molding, extrusion molding, and

18

Engineering Thermoplastics: Polyolefins and Styrenics

compression molding. In the production of heat curing type ring opening polymers, ring opening polymerization catalysts of high activity are selected and used for shortening the reaction time in the mold, whereby crosslinked cured polymers can be obtained. Thermoplastic dicyclopentadiene ring opening polymers and their hydrogénation products are excellent in balancing various properties, such as heat resistance, transparency, water resistance, chemical resistance, electric properties, low birefringence, and stiffness. Therefore, they are used in a wide variety of fields, for example, as optical materials, medical equipment, electrical insulating materials and electronic part processing materials. The materials are fabricated by various molding methods, such as injection molding, extrusion molding, compression molding, and solvent casting. Thermoplastic dicyclopentadiene ring opening polymers can be obtained by polymerizing dicyclopentadiene in the presence of a metathesis catalyst. Hydrogenated products can be obtained by hydrogenating the double bonds in the backbone. The hydrogénation results in improvement of various properties, such as heat resistance, weathering resistance, light resistance, etc. The properties can be still improved by adding suitable comonomers (6). Various molded products can be made from the materials. In particular, transparent molded products can be obtained. The materials exhibit excellent mechanical strength, such as impact resistance, low permeation of water or water vapor and excellent solvent resistance. Therefore, they can be used for optical uses such as lens, prisms, and polarizing films. Further, they can be used for medical purposes, such as pressthrough packages, disposable syringes, liquid medicine vials, and infusion bags. They are suitable for electric or electronic materials, such as wire coating. In addition, packaging films, such as wrapping films, stretch films, shrink films, and blister packs can be produced. 1.2.6

Copolymers

The preparation of copolymers and block copolymers does not make problems. For example, cyclopentadiene can be copolymerized with norbornene using the following procedure. Cyclopentadiene and the norbornene are mixed with benzene and added to the reactor

Metathesis Polymers

19

vessel. 1-Butene is added in 2% solution in benzene. Ethylaluminum sesquichloride, (CHsCJ-^bA^Cb, is added as a 0.5 molar solution in benzene followed by the addition of the tungsten hexachloride (0.20 molar in ethyl acetate or 0.05 molar in benzene). The reactions are conducted at about 25°C under stirring. The copolymerization reaction proceeds to completion in a short time and produces viscous smooth polymers (13). Block polymers may be formed by allowing polymerizing with a single monomer. When the reaction is essentially finished, a second monomer is added. This means that the end groups are virtually living. The molybdenum-based catalyst MoOCl2(t-BuO)2 has been used to copolymerize norbornene and dicyclopentadiene (20). The polymeric product exhibits a single peak in gel permeation chromatography. 2.2.7

Thermosets

Common thermosets are cured by a free radical addition mechanism. These types of composites are cured by heat initiators, such as peroxides, or by photo initiators, such as a-diketones. A characteristic of cured acrylates is large shrinkage in the course of polymerization, which is undesirable for many uses. Another undesirable characteristic of acrylates is the formation of an oxygen-inhibited layer on the surface upon curing. Another type of thermoset polymers is based on epoxy monomers. These thermosets are cured by use of a two-component system or by photo initiators. Disadvantages of epoxies are high water uptake in service and polymerization shrinkage (22). Compositions that are curing by the principle of ROMP have been added to the spectrum of thermosets. These may be either one part compositions and two part compositions. The materials have a remarkably low shrinkage on curing. Therefore, typical applications are in the fields of dental applications or in automotive and electronic applications. A dinorbornenyl dicarboxylate ester (DNBDE) is synthesized by the Diels-Alder reaction of cyclopentadiene with diacrylates, as shown in Figure 1.10. Alternatively, a DNBDE may be synthesized

20

Engineering

Thermoplastics:

Polyolefins

and

Styrenics

.0—R—O.

0-R-

Figure 1.10: Diels-Alder Reaction of Cyclopentadiene with a Diacrylate (A). Diels-Alder Reaction of Cyclopentadiene with an Adduct of an Acrylate with Succinic Acid (B). The Product can be Dimerized with PEG.

via an esterification reaction. Cyclopentadiene can be reacted with the adduct of 2-hydroxyethyl acrylate with succinic anhydride to give a norbornenyl functional carboxylic acid (A), cf., Figure 1.10. This is followed by esterification of (A) with PEG 400 using p-toluenesulfonic acid as a catalyst in cyclohexane with azeotropic removal of water (22). In a similar way, norbornene 2-ethylhexyl carboxylate, norbornene isobornyl carboxylate, norbornene phenoxyethyl carboxylate, (5) are and related monomers are obtained. As catalysts, osmium or ruthenium catalysts similar to those shown in Figure 1.8 are used. In addition, one component compositions comprise a reaction

Metathesis Polymers

21

Table 1.7: Shrinkage of Resin Compositions (22) Monomer Type3

Shrinkageb/[%]

Aliphatic Acrylate Resin Aromatic Methacrylate Resin ROMP polymerized a Neat resin compositions, without filler b Volumetric shrinkage

9.2 6.75 3.75

control agent, i.e., tetraallyl silane, which influences the kinetics of the reaction. The control reaction agent slows the metathesis reaction and thereby allows for an increase in the induction period before cure, or the pot life. Curing is achieved by heating to a temperature of 60-150°C. In a two-component composition, the base paste contains the monomer and the catalyst paste contains the catalyst, which after mixing of the catalyst paste with the base paste, initiates the metathesis reaction of the olefinic substrate. Clearly, for two part compositions, a reaction control agent may be used if desirable as a component of the base paste. Typical shrinkages of ROMP polymerized compositions and comparative values are shown in Table 1.7. 1.2.8 Reinforced Polymer

Composites

Reinforced composite materials are widely used as structural materials for aerospace, automotive, and construction applications. These materials provide desirable properties, such as high stiffness and strength. Composites typically include a continuous matrix phase, usually a polymeric material or a ceramic material and a reinforcement phase. The reinforcement phase can be made of inorganic materials, including metals, ceramics, and glasses; or organic materials, including organic polymers and carbon fibers. Particularly good properties are obtained when the reinforcement phase contains fibrous materials (30). The manufacture of fiber reinforced composites involves the combination of the fiber reinforcement and a liquid precursor to the matrix in a mold, followed by solidification of the liquid and formation of the matrix. This solidification can be the result of chemical reac-

22

Engineering Thermoplastics: Polyolefins and Styrenics

fions, in which case the liquid precursor is referred to as a reactive liquid. Although the reinforcing fibers may be present in the liquid precursor prior to dispensing, better properties are typically obtained when the fibers are initially present in the mold as a preform. The liquid is then dispensed into the mold such that the final matrix fills the mold and surrounds the fibers. Preforms may be arranged as mats or meshes. The fibers within the preform may be randomly oriented or may be oriented in one or more directions. The performance of composites is influenced by many factors, including the amount of reinforcement present relative to the matrix, referred to as fiber loading and the degree of contact between the fibers and the matrix. Both strength and stiffness tend to be improved by an increase in fiber loading and by increased contact between the phases. To ensure sufficient contact between the fibers and the matrix, it is desirable to use a liquid precursor with a low viscosity. Reactive liquids are usually preferred over thermoplastics due to the low viscosity of liquids relative to polymer melts. The reactive liquid is typically a multi-component mixture. The reactive liquid may contain a monomer and an activator, which will cause the monomer to polymerize into a solid polymer matrix. In RIM processes, two or more reactive components are mixed together, starting the reaction between the components before the mixture is dispensed into the mold. This tends to increase the viscosity of the liquid that is dispensed due to an increase in molecular weight of the polymers or pre-polymers formed in the initial reaction. An increased viscosity can prohibit complete filling of the mold and permeation of the preform. This tends to decrease the adhesion between the matrix and the fibers. Poor interfacial adhesion between the reinforcement and matrix phase can cause a material to have less than desirable stiffness and strength. Norbornene polymers or polymers from dicyclopentadiene, respectively, may be formed by the interaction of a cyclic olefin with a ROMP catalyst. Increased reinforcement density provides for extremely high stiffness and strength in poly(norbornene) composites. As catalyst, Phenylmethylene-bis-(tricyclohexylphosphine) ruthenium dichloride is used (30).

Metathesis Polymers

23

1.2.9 Polymers ivith Functional Groups As mentioned before, problems with monomers with functionalities with acid hydrogen have been encountered with some types of catalysts. Now, the direct incorporation of polar functional groups along the backbone of linear polymers made via ROMP is possible due to the development of functional group-tolerant late transition metal olefin metathesis catalysts (10). The ROMP of alcohol, ketone, halogen, and acetate substituted cyclooctenes with a ruthenium olefin metathesis catalyst has been reported (31). The interest of functional polymers originates among others in the fact that for example, the hydroxyl group imparts barrier properties of the polymer. The asymmetry of the substituted cyclooctene allows for head-tohead (HH), head-to-tail (HT), and tail-to-tail (TT) coupling, yielding a polymer with regio-random placement of the functional groups. A similar problem was encountered by the ROMP of a borane substituted cyclooctene with an early transition metal catalyst followed by oxidation to yield an alcohol-functionalized linear polymer (32). However, the regio-random distribution of functional groups can be avoided by an acyclic diene metathesis (ADMET) polymerization technique using symmetric monomers (33). The molecular weights of these polymers are restricted to < 3 x 104 Dalton by ADMET. Due to their rich hydrocarbon content, the barrier properties in final ethylene vinyl alcohol copolymers are reduced. The ROMP of alcohol or acetate disubstituted cyclopentene monomers is not possible by catalysts such as (PCy 3 ) 2 (Cl) 2 Ru=CHPh and (IMesH 2 )(PCy 3 )(Cl) 2 Ru=CHPh. Mes represents mesityl (2,4,6-trimethylphenyl), Ph is phenyl and Cy is a cyclohexyl radical. Ruthenium bisphosphine complexes (PCy 3 ) 2 (Cl) 2 Ru = CHPh

24

Engineering Thermoplastics: Polyolefins and Styrenics

Figure 1.11: Monomer with UV-absorbing Functionality: (4-(Bicyclo[2.2.1]hept-5-en-2-ylmethoxy)-2-hydroxyphenyl)phenyl-methanone are somewhat more reactive. Completely regio-regular polymers can be prepared by using a symmetric bicyclic or polycyclic olefin as the monomeric substrate for the ROMP reaction. In order to synthesize telechelic polymers, the ROMP reaction is carried out in the presence of acyclic olefins that act as chain transfer agents to regulate the molecular weight of the polymers produced. When a, ω-difunctional olefins are employed as chain transfer agents, difunctional telechelic polymers can be synthesized. Such difunctional olefins are the preferred chain transfer agents. When carrying out a ROMP reaction using a symmetric a, ω-difunctional olefin as a chain transfer agent, the propagating alkylidene generated during the ring opening metathesis process is terminated with a functional group. The new functionally substituted alkylidene reacts with a monomer to initiate a new polymer chain. This process preserves the number of active catalyst centers and leads to symmetric telechelic polymers with a functionality that approaches 2. The only polymeric end groups that do not contain residues from the chain transfer agent are those from the initiating alkylidene and the endcapping reagent. Basically, these end groups could be chosen to match the end group from the chain transfer agent. Monomers with UV-absorbing functionality, such as shown in Figure 1.11 can be copolymerized with norbornene to have the UVabsorber bond to the polymeric backbone. (4-(Bicyclo[2.2.1]hept-5en-2-ylmethoxy)-2-hydroxyphenyl)phenyl-methanone is prepared by first synthesizing 4-allyl-2-hydroxyphenyl-phenyl-methanone

Metathesis Polymers

25

Table 1.8: Compounds with UV-absorbing Groups (34) Compound (2,4-Dihydroxyphenyl)-phenylmethanone 2-Benzotriazol-2-yl-4-methylphenol 4-Benzotriazol-2-ylbenzene-l,3-diol 3-[3-ferf-Butyl-5-(5-chlorobenzotriazol-2-yl)-4-hydroxyphenyl]-propionic acid 3-[5-(Benzotriazol-2-yl)-3-ferf-butyl-4-hydroxyphenyl]-propionic acid 4-(4,6-Diphenyl)-l,3,5-triazin-2-yl-benzene-l,3-diol 4-[4,6-Bis-(biphenyl-4-yl)-l,3,5-triazin-2-yl]-benzene-l,3-diol 4-[4,6-Di-(2,4-dihydroxyphenyl)-l,3,5-triazin-2-yl]-benzene-l,3-diol N'-2-Ethylphenyl-N'-2-hydroxyphenyloxalamide from allyl bromide and 2,4-dihydroxybenzophenone and then allowing a Diels-Alder reaction with dicyclopentadiene. Dicyclopentadiene decomposes into cyclopentadiene before the Diels-Alder reaction occurs. Oligomers with 1-hexene as comonomer with a degree of polymerization of around 10 are prepared and the double bonds in the oligomeric chains are hydrogenated subsequently (34). For the preparation of the oligomer, as catalyst, bis-(tricyclopentylphosphine)-dichloro(3-methyl-2-butenylidene) ruthenium (APT Cat ASMC 716) is used. A pale brown solid with a melting range of 88-94°C and a number-average molecular weight M„ of 5900 Dalton is obtained. Besides of (2,4-dihydroxyphenyl)-phenylmethanone, many other compounds with suitable UV-absorbing groups can be used. These compounds are listed in Table 1.8. The oligomeric UV-absorber is mixed with low density poly(ethylene) in a typical formulation, with an amount of 0.8% by weight. 1.2.10

Poly(acetylene)s

In 1975, it was discovered that WC16, which is a typical metathesis catalyst, is capable to catalyze the polymerization of phenylacetylene. Subsequently, various substituted acetylenes have been polymerized by this type of catalyst. In 1983, poly(l-(trimethylsilyl)-lpropyne)) was synthesized in the presence of TaCls and NbCls (35). The alkyne polymerization has many similarities with ROMP.

26

Engineering Thermoplastics: Polyolefins and Styrenics

The polymerization of substituted alkynes is postulated to proceed either by the metathesis mechanism or by an insertion mechanism (18). Numerous alkyne dérivâtes have been shown to polymerize in the presence of group V, VI, and VIII transition metal catalysts.

1.3

Properties

2.3.1 Mechanical

Properties

trans-Polypentenamer can be obtained from cyclopentene by ROMP. This material is highly commended. The glass transition temperature is close to natural rubber. The c/s-isomer, cz's-polypentenamer has the lowest glass transition temperature of any known hydrocarbon polymer of -113°C (36). 1.3.2

Optical Properties

Transparent resins are used as the materials for molded products, such as automobile components, illumination equipment, and electrical components. Transparent resins, which can be applied to such applications, include poly(carbonate) (PC)-based resins and acrylicbased resins. However, although acrylic-based resins offer excellent transparency, they have problems in terms of heat resistance and water resistance. In contrast, PC-based resins offer superior performance to acrylic resins in terms of heat resistance and water resistance, but suffer from different problems, such as a high birefringence. Certain norbornene derivatives, for example, 5-(2-naphthalenecarbonyloxy)bicyclo[2.2.1]hept-2-eneor5-(4-biphenylcarbonyloxy)bicyclo[2.2.1]hept-2-ene produce a polymer that is effective in producing molded products with excellent transparency, low water absorption, and low birefringence (29). The norbornene derivative is polymerized by a ring opening metathesis polymerization, followed by a hydrogénation reaction. The polymers can be used for optical disks, optical lenses, and optical films or sheets.

Metathesis Polymers

27

Figure 1.12: Fluorinated Monomers Suitable for ROMP (36)

1.4

Fabrication Methods

The best known polymerization of norbornene is the ring opening metathesis polymerization. The reaction is technically applied in the Norsorex process (7).

1.5

Fluorinated Polymers

The synthesis of highly fluorinated cyclopentenes by ROMP is not successful. This is attributed to the free energy of polymerization of five membered rings, which is close to zero. This obstacle can be overcome by moving electron withdrawing substituents away from the double bond and increasing the reactivity of double bond by positioning it in a strained ring. This is achieved using bicyclic monomers. The monomers are readily obtained from the Diels-Alder reactions of substituted olefins with cyclopentadiene. This route is effective also for fluorinated monomers. These types of monomers undergo a ROMP with a variety of one component and two-component initiator systems. A wide variety of fluorinated monomers has been investigated with respect to the ability to undergo ROMP. Examples are shown in Figure 1.12.

28

Engineering Thermoplastics: Polyolefins and Styrenics

The catalysts were synthesized either from the reaction of transition metal chlorides, WC16/ M0CI5, OsCl 3 , RuCl 3 , IrCl 3 , ReCl5 with the monomers, or generated by reactions of the transition metal chlorides with alkylating agents, such as Pl^Sn, Bu4Sn, (CH3)4Sn, etc.

1.6

Special Additives

In general, any additives that are common in the polyolefin sector can be used to achieve the desired properties. We will summarize additives for thermoplastic metathesis polymers. These include (6): • • • • • • • •

Plasticizers, Foaming Agents, Flame Retardants, Antioxidants, Near infrared absorbers, Antistatic agents, Lubricants, and Anti-fogging agents.

Plasticizers include tricresyl phosphate and trixylyl phosphate. Foaming agents can be added in the case of using the polymers for wires, which require low dielectric constant and low dielectric loss tangent, such as communication cables, coaxial cables for computers and high-frequency cables. Flame retardants are preferably added for wires, such as highvoltage power cables through with a large quantity of current flows. Antioxidants include phenolic antioxidants, phosphorus antioxidants and sulfur antioxidants. Near infrared absorbers include cyanin compounds, pyrylium compounds, phthalocyanine compounds, and dithiol metal complexes. Antistatic agents include long chain alkyl alcohols and fatty acid esters with polyhydric alcohols. Stearyl alcohol and behenyl alcohol are the especially preferred compounds. Anti-fogging agents include sorbitan fatty acid esters and glycerin fatty acid esters.

Metathesis Polymers

1.7

29

Applications

Thermoplastic cyclic olefin polymers can be used for a wide range of applications, such as wire coating materials, agricultural films, and packaging films, and toner resins. Further, optical applications such as plate lenses, including Fresnel lenses have been described (6). 1.7.1 Packaging Films Copolymers of ethylene and norbornene exhibit excellent transparency, high moisture barrier, high strength and stiffness, and low shrinkage. In comparison to poly(ethylene) (PE) and polypropylene) (PP), they show a very low gas permeability. They are used for blister packaging in pharmacy applications and for flexible films for food packaging. Multilayer films consisting of PP outer layers and a cyclic olefin copolymer are in use. 1.7.2

Wire Coating

Materials

The product of hydrogénation of a thermoplastic dicyclopentadiene ring opening polymer may be used as wire coating materials. Crosslinking agents, foaming agents, flame retardants, and other polymers can be added to the formulation (6). As crosslinking agents, organic peroxides, or photosensitive initiators can be used. Foaming agents can be added for the fabrication of wires, which require low dielectric constant and low dielectric loss tangent, such as communication cables, coaxial cables for computers, and highfrequency cables. Examples of foaming agents are sodium bicarbonate, ammonium bicarbonate and nitroso compounds. Especially, when dinitrosopentamethylenetetramine is used, foaming aids can be added that accelerate the decomposition and reduce the decomposition temperature. This is achieved, for example, with salicylic acid, or with urea. Various chlorine and bromine flame retardants can be used as halogen-based flame retardants, e.g., tetrabromobisphenol A dérivâtes. The wire coating material can be coated on a conductor by coextruding the conductor and the molten material in an extrusion molding machine. The compound is provided in the form of pellets.

30

Engineering Thermoplastics: Polyolefins and Styrenics

The same extruder as in wire coating with PE can be used. However, since the cyclic olefin polymer composition has a higher in glass transition temperature than PE, the cylinder temperature of the extruder must be set to a somewhat higher temperature than used in the conventional method. When the material is dissolved in an organic solvent and provided as a varnish, the varnish can be directly coated on the conductor. These methods can be optionally selected according to the thickness of the coating material and other desired properties. 1.7.3 Chromatographie

Supports

There are various types of supports used in chromatography, including inorganic supports based on silica, zirconia, titania or aluminum oxide, further, organic supports based on crosslinked polystyrene), poly(acrylate), and poly(methyl methacrylate). More recent developments are the preparation using sol-gel technology, and ROMP polymerization. The various issues are reviewed in the literature (37). Monolithic materials were introduced in separation science in the late 1960s. There is a perpetual progress in this topic (38). Support materials for solid phase extraction (SPE) and for Chromatographie techniques have been prepared by ROMP. pH-stable high capacity stationary phases have been prepared by copolymerization of functional monomers with a suitable crosslinking agent, with precipitation polymerization techniques. The suspension polymerization of norborn-5-ene-2,3-dicarboxylic anhydride in dichloromethane using a molybdenum-based initiator results in living, linear polymer chains with the active initiator at the polymer chain end. The solubility of the poly(norborn-5-ene2,3-dicarboxylic anhydride) is dependent on the chain length. Oligomers with a degree of polymerization up to 10-15 are soluble, whereas higher oligomers are insoluble. Thus, by adjusting an appropriate degree of polymerization, a precipitation type polymerization can be achieved. In the second stage a crosslinking agent, e.g., l,4,4a,5,8,8a-hexahydro-l,4,5,8-dimethanonaphthalene is added, which forms the crosslinked matrix. A polymer is formed where the linear oligomer chains are fixed at the crosslinked matrix as pendent groups.

Metathesis Polymers

31

In the last stage of polymerization the products are endcapped with ferrocenealdehyde or benzaldehyde in order to remove the molybdenum catalyst from the material (19). The actual removal of catalyst occurs by a treatment with aqueous sodium hydroxide, which is followed by a treatment with hydrochloric acid. Thereby the anhydride functionalities are hydrolyzed (39). The materials were tested as supports for SPE techniques. Excellent recoveries are observed, exceeding silica-based SPE materials (40). The supports were also investigated for their retention behavior for phenols, alcohols, carboxylic acids, aldehydes, ketones, esters, chloroalkenes, and polycyclic aromatic hydrocarbons (41). In the same way, dipyridyl amide-functionalized supports suitable for the SPE of metal ions from aqueous solutions can be prepared. The resins are synthesized via the copolymerization of the functional monomer eiiifo-norbornene-5-yl-N,N-di-2-pyridyl carboxylic amide with a molybdenum-based catalyst (42). Essentially no loss of performance was observed after extensive use over more than twenty cycles. After exposure to air for at least 2 months, a change in color from bright white to yellow was observed. However, this change in color did not influence the characteristic properties of the resins. Separations of enantiomers can be achieved by chiral chromatography. Even, when the enantioselective synthesis of drugs and pharmaceuticals is possible, a major part of chiral compounds is still produced as a racemate and needs to be separated into the enantiomers by chiral high performance liquid chromatography. Chiral stationary phases (CSP) have been synthesized by ROMP techniques. The separation of dinitrobenzoylphenylalanine can be achieved on a poly(N-(norborn-5-ene-2-carboxyl)-L-phenylalanine ethylester) grafted to Nucleosil 300-5 (43). Norbornene was functionalized with cyclodextrins and surface grafted onto silica-based supports using ROMP (44). The CSP are suitable for the enantioselective separation various amino acids, including ß-blockers and other compounds, such as chiral ferrocene dérivâtes. Materials prepared by the ROMP technique find use in monolithic capillary columns (45,46), and monolithic membrane discs (47). A monolithic column is a column in which the stationary phase is

32

Engineering Thermoplastics: Polyolefins and Styrenics

COOH

Figure 1.13: Functional Monomers Used for Monolith Grafting: 7-Oxabicyclo[2.2.1]hept-5-ene-2-carboxylic acid (I), 7-Oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid anhydride (II), and N-Phenyl-7-oxabicyclo[2.2.1]5-heptene-2,3-dicarboximide (III) cast as a solid, porous rod. Traditionally, the stationary phase is packed in form of particles into the column. In the present context, crosslinked, functionalized organic polymers can find application as monolithic stationary phase. In the case of capillary columns, in the initial step of preparation the surface is modified with bicyclo[2.2.1]hept-2-en-5-ylmethyldichlorosilane. This acts as an anchor for subsequent ROMP polymerization. Some functional monomers used for monolith grafting are shown in Figure 1.13.

1.8

Suppliers and Commercial Grades

Industrially, ROMP is used for the production of cheap highly unsaturated polymers e.g., Norsorex, Vestenamer. For example, poly(norbornene) is produced in quantities of around 5 k t a " 1 , under the tradename of Norsorex (18). Examples for commercially available grades and tradenames are shown in Table 1.9. Tradenames appearing in the references are shown in Table 1.10.

Metathesis

Polymers

33

Table 1.9: Examples for Commercially Available Metathesis Polymers Tradename Producer Remarks Vestenamer® Norsorex® Norsorex® Telene Metton® Zeonex® Arton® Topas®

Degussa AG Arkema Corp. CDF Chimie BF Goodrich Hercules Nippon Zeon Japan Synthetic Rubber Daicel

Poly(octenamer) Poly(norbornene) Poly(norbornene) Cyclic olefin polymer Cyclic olefin copolymer Ethylene and norbornene copolymers

34

Engineering Thermoplastics:

Tradename Description

Polyolefins

and

Styrenics

Table 1.10: Tradenames in References Supplier

Chimassorb® 81 Ciba Geigy 2-Hydroxy-4-(octyloxy)benzophenone(23) Dowlex® NG 5056E Dow 1-Octene/ethene copolymer (LLDPE) (34) Dyneema® DSM High Performance Fibres Gel-spun poly(ethylene) fiber in thermoplastic rubber matrix (23) Ethanox® 330 Albemarle Corp. l,3,5-Trimethyl-2,4,6-tris(3,5-di-ferf-butyl-4-hydroxybenzyl)benzene (23) Ethanox® 702 Albemarle Corp. 4,4'-Methylenebis(2,6-di-íerf-butylphenol)(23) Hitacol Hitachi Kasei K.K. Poly(sulfide) (15) Irgafos® 168 Ciba Specialty Chemicals Tris(2,4-di-ferf-butylphenyl)phosphite (23,34) Irganox® 1010 Ciba Geigy Pentaerythritol tetrakis(3-(3,5-di-ferf-butyl-4-hydroxyphenyl)propionate), phenolic antioxidant (23) Irganox® 1076 Ciba Geigy Octadecyl-3-(3',5'-di-feri-butyl-4'-hydroxyphenyl) propionate (23) JSR BR-01 Japan Synthetic Rubber Co. cis-l,4-Poly(butadiene) (15) Kevlar® DuPont Aramid (23) Naugard® XL-1 Uniroyal Chemical Co. N,N'-Bis[2-(3-[3,5-di-ferf-butyl-4-hydroxyphenyl]propionyloxy)ethyl]-oxamide (34) Riblene® FF 29 Enichem LDPE pellets (34) Tinuvin® 144 Ciba Geigy Bisíl^^ó/ó-pentamethyl^-piperidinyl) butyl(3,5-di-ferf-butyl-4-hydroxybenzyl)malonate, UV absorber (23) Tinuvin® 327 Ciba Geigy 2,4-Di-terf-butyl-6-(5-chloro-2H-benzotriazol-2-yl)phenol, UV absorber (23)

Metathesis

Polymers

35

Table 1.10 (cont): Tradenames in References Tradename Description

Supplier

Tinuvin® 328 Ciba Geigy 2-(2'-Hydroxy-3',5'-di-ferf-amylphenyl)benzotriazole, UV absorber(23) Tinuvin® P Ciba Geigy 2-(2'-Hydroxy-5'-methylphenyl)benzotriazole, UV absorber (34) Twaron® Teijin Twaron B.V. Aramid (23) Ultrene® Cymetech, LLC. Dicyclopentadiene (23) Viron-200 Toyo Boseki K.K. Polyester (15) Wingstay® SN-1 Goodyear Tire & Rubber Co. (3,6,9-Trioxaundecyl)bis(dodecylthio)propionate, antioxidant for the vulcanization of rubber (23) Zylon® Toyobo Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber (23)

1.9

Safety

Cyclopentene a n d n o r b o r n e n e are highly flammable a n d harmful in contact w i t h skin, eyes a n d the respiratory system. For poly(norbornene) n o special h a z a r d s are reported. O n h a n d l i n g , the usual precautions should be applied.

References 1. H.S. Eleuterio, Verfahren zur Polymerisation cyclischer, insbesondere mono-, bi-, oder tricyclischer Olefine, DE Patent 1072811, assigned to E. I. Du Pont de Nemours and Company (Wilmington, DE), January 7,1960. 2. H.S. Eleuterio, Polymerization of cyclic olefins, US Patent 3 074 918, assigned to E. I. Du Pont de Nemours and Company (Wilmington, DE), January 22,1963. 3. J.L. Hérisson and Y. Chauvin, Catalysis of olefin transformations by tungsten complexes. II telomerization of cyclic olefins in the presence of acyclic olefins, Makromol. Client., 141:161-176,1971.

36

Engineering Thermoplastics:

Polyolefins

and

Styrenics

4. R.H. Grubbs, The olefin metathesis reaction, Prog. Inorg. Chem., 24:150,1978. 5. W.J. Feast, E. Khosravi, and T. Leejarkpai, Process for polymerization of cycloolefins and polymerizable cycloolefins, US Patent 6677418, assigned to University of Durham (Durham, GB), January 13,2004. 6. K. Obuchi, M. Tokoro, T. Suzuki, H. Tanisho, and K. Otoi, Thermoplastic dicyclopentadiene-base open-ring polymers, hydrogenated derivatives thereof, and processes for the preparation of both, US Patent 6511 756, assigned to Nippon Zeon Co., Ltd. (Tokyo, JP), January 28, 2003. 7. C. Janiak and PG. Lassahn, Metal catalysts for the vinyl polymerization of norbornene, /. Mol. Catal. A: Chem., 166(2):193-209, February 2001. 8. G. Suld, A. Schneider, and H.K. Myers, Jr., Process for preparing solid polymers of norbornadiene, US Patent 4100338, assigned to Sun Oil Company of Pennsylvania (Philadelphia, PA), July 11,1978. 9. G. Dall'asta and G. Motroni, Site of ring cleavage in the ring-opening polymerization of low strained cycloolefins, Eur. Polym. }., 7(6):707716,1971. 10. R.H. Grubbs, O.A. Scherman, and H.M. Kim, Ring-opening metathesis polymerization of bridged bicyclic and polycyclic olefins containing two or more heteroatoms, US Patent 6 884 859, assigned to California Institute of Technology (Pasadena, CA), April 26, 2005. 11. A.V. Ambade and A. Kumar, Controlling the degree of branching in vinyl polymerization, Prog. Polym. Sei., 25(8):1141-1170, October 2000. 12. C. W. Bielawski and R.H. Grubbs, Living ring-opening metathesis polymerization, Prog. Polym. Sei, 32(l):l-29, January 2007. 13. R.J. Minchak, Process for preparing polymers of cyclopentadiene and bicycloheptene mixtures, US Patent 4138 448, assigned to The B. F. Goodrich Company (New York, NY), February 6,1979. 14. K.J. Ivin, "Metathesis polymerization," in H.F. Mark, N. Bikales, C.G. Overberger, and G. Menges, eds., Encyclopedia of Polymer Science and Engineering, Vol. 9, pp. 634-688. Wiley Interscience, New York, 2nd edition, 1988. 15. Y Kobayashi, T. Ueshima, and S. Kobayashi, Process of producing ring-opening polymerization products, US Patent 4080491, assigned to Showa Denko K.K. (Tokyo, JA), March 21,1978. 16. J.-F. Lahitte, F. Pelascini, F. Peruch, S.P. Meneghetti, and P.J. Lutz, Transition metal-based homopolymerisation of macromonomers, Compt. Rendus Chem., 5(4):225-234, April 2002. 17. R. Godoy Lopez, F. D'Agosto, and C. Boisson, Synthesis of well-defined polymer architectures by successive catalytic olefin polymeriza-

Metathesis

18. 19. 20. 21. 22. 23.

24.

25. 26.

27.

28. 29.

30.

Polymers

37

tion and living/controlled polymerization reactions, Prog: Polym. Sei., 32(4):419-454, April 2007. J.R Claverie and R. Soula, Catalytic polymerizations in aqueous medium, Prog. Polym. Sei., 28(4):619-662, April 2003. M.R. Buchmeiser, Metathesis polymerization-derived Chromatographie supports, /. Chromatogr. A, 1060(l-2):43-60, December 2004. S.L. Mukerjee and V.L. Kyllingstad, Ring-opening metathesis polymerization (romp) of cyclo-olefins with molybdenum catalysts, US Patent 6433113, assigned to Zeon Corporation (Tokyo, JP), August 13,2002. T. Weskamp, W.C. Schattenmann, M. Spiegler, and W.A. Herrmann, A novel class of ruthenium catalysts for olefin metathesis, Angew. Chetn. Int. Ed., 37(18):2490-2493,1998. C. Angeletakis, Metathesis-curable composition, US Patent 7 001590, assigned to Kerr Corporation (Orange, CA), February 21, 2006. R.H. Grubbs, J. Louie, J.P. Morgan, and J.L. Moore, Highly active metathesis catalysts generated in situ from inexpensive and air stable precursors, US Patent 6610626, assigned to Cymetech, LLP (Huntsville, TX); California Institute of Technology (Pasadena, CA), August 26,2003. R.H. Grubbs, P. Schwab, and S.T. Nguyen, High metathesis activity ruthenium and osmium metal carbene complexes, US Patent 6 806 325, assigned to California Institute of Technology (Pasadena, CA), October 19, 2004. C.S. Woodson, Jr. and R.H. Grubbs, Polymeric composites including dicyclopentadiene and related monomers, US Patent 6310121, assigned to Cymetech, LLC (Huntsville, TX), October 30, 2001. R. Grubbs, C. Bielawski, and D. Benitez, Synthesis of macrocyclic polymers by ring insertion polymerization of cyclic olefin monomers, US Patent 6946533, assigned to California Institute of Technology (Pasadena, CA), September 20,2005. D.M. Lynn, E.L. Dias, R.H. Grubbs, and B. Mohr, Acid activation of ruthenium metathesis catalysts and living ROMP metathesis polymerization in water, US Patent 6 486 279, assigned to California Institute of Technology (Pasadena, CA), November 26,2002. B. Mohr, D.M. Lynn, and R.H. Grubbs, Synthesis of water-soluble, aliphatic phosphines and their application to well-defined ruthenium olefin metathesis catalysts, Organometallics, 15(20):4317-4325,1996. N. Miyaki, Y. Miyamoto, S. Fukuhara, and T. Ootsuki, Norbornene derivative and norbornene polymer obtained therefrom through ring opening polymerization, US Patent 6 846 890, assigned to JSR Corporation (Tokyo, JP), January 25, 2005. M.R. Kessler, S.R. White, and B.D. Myers, Catalyzed reinforced polymer composites, US Patent 6 750 272, assigned to Board of Trustees of

38

Engineering Thermoplastics:

Polyolefins

and

Styrenics

University of Illinois (Urbana, IL), June 15, 2004. 31. M.A. Hillmyer, W.R. Laredo, and R.H. Grubbs, Ring-opening metathesis polymerization of functionalized cyclooctenes by a rutheniumbased metathesis catalyst, Macromolecules, 28(18):6311-16,1995. 32. S. Ramakrishnan and T.C. Chung, Poly(5-hydroxyoctenylene) and its derivatives: Synthesis via metathesis polymerization of an organoborane monomer, Macromolecules, 23(21):4519-24,1990. 33. M.A.J. Schellekens and B. Klumperman, Synthesis of polyolefin block and graft copolymers, /. Macromol. Set., Rev. Macromol. Chem. Phys., C40(2-3):167-192, 2000. 34. A. Zedda, D. Lazzari, M. Sala, M. Bonora, M. Vitali, and P.A. Van Der Schaaf, ROMP with oligomeric UV-absorbers, US Patent 6 864 325, assigned to Ciba Specialty Chemicals Corporation (Tarrytown, NY), March 8, 2005. 35. K. Nagai, T. Masuda, T. Nakagawa, B.D. Freeman, and I. Pinnau, Poly[l-(trimethylsilyl)-l-propyne] and related polymers: Synthesis, properties and functions, Prog. Polym. Sei, 26(5):721-798, June 2001. 36. J.W. Feast and E. Khosravi, Synthesis of fluorinated polymers via ROMP: A review,/. Fluorine Chem., 100(1-2):117-125, December 1999. 37. M.R. Buchmeiser, New synthetic ways for the preparation of highperformance liquid chromatography supports, ]. Chromatogr. A, 918 (2):233-266, May 2001. 38. M.R. Buchmeiser, Polymeric monolithic materials: Syntheses, properties, functionalization and applications, Polymer, 48(8):2187-2198, April 2007. 39. M.R. Buchmeiser and F.M. Sinner, Functionalized supporting materials which can be obtained by means of metathesis graft polymerization, WO Patent 0061288, assigned to Merck Patent Gmbh (DE); Buchmeiser Michael Rudolf (AT); Sinner Frank Michael (AT), October 19, 2000. 40. M.R. Buchmeiser and G.K. Bonn, Separation polymers, AT Patent 404099, August 25,1998. 41. D.L. Ambrose, J.S. Fritz, M.R. Buchmeiser, N. Atzl, and G.K. Bonn, New, high-capacity carboxylic acid functionalized resins for solidphase extraction of a broad range of organic compounds, /. Chromatogr. A, 786(2):259-268, October 1997. 42. M.R. Buchmeiser, R. Tessadri, F. Sinner, and G.K. Bonn, Dipyridylamine ligand bound to a polymer carrier for extracting metal ions, AT Patent 405 056B, May 25,1999. 43. M.R. Buchmeiser, F. Sinner, M. Mupa, and K. Wurst, Ring-opening metathesis polymerization (ROMP) for the preparation of surfacegrafted polymer supports, Macromolecules, 33(l):32-39, January 2000.

Metathesis

Polymers

39

44. B. Mayr, F. Sinner, and M.R. Buchmeiser, Chiral beta-cyclodextrinbased polymer supports prepared via ring-opening metathesis graftpolymerization, /. Chromatogr. A, 907(l-2):47-56, January 2001. 45. B. Mayr, G. Hölzl, K. Eder, M.R. Buchmeiser, and H.C. G., Hydrophobie, pellicular, monolithic capillary columns based on cross-linked polynorbornene for biopolymer separations, Anal. Chem., 74(23):60806087, December 2002. 46. C. Gatschelhofer, C. Magnes, T.R. Pieber, M.R. Buchmeiser, and F.M. Sinner, Evaluation of ring-opening metathesis polymerization (ROMP)-derived monolithic capillary high performance liquid chromatography columns, /. Chromatogr. A, 1090(l-2):81-89, October 2005. 47. S. Lubbad, S.A. Steiner, J.S. Fritz, and M.R. Buchmeiser, Metathesis polymerization-derived monolithic membranes for solid-phase extraction coupled with diffuse reflectance spectroscopy, /. Chromatogr. A, 1109(1):86-91, March 2006.

This Page Intentionally Left Blank

2 Cyclic Olefín Copolymers Cyclic olefín copolymers (COC)s are engineering thermoplastics derived from norbornene. An addition polymer of norbornene was originally described in 1955 (1). Basically, COCs can be manufactured by ring opening metathesis polymerization (ROMP) as described in the chapter about metathesis polymers. However, ROMP offers disadvantages as main chain double bonds must be hydrated after polymerization. Therefore, COCs are more conveniently straightforwardly prepared by addition polymerization.

2.1

Monomers

Monomers are shown in Table 2.1 and in Figure 2.1. The most important monomer is norbornene. Norbornene is in made from dicyclopentadiene (DCPD) and etheneby a Diels-Alder reaction. 5-Triethoxysilyl-2-norbornene is used for crosslinkable compositions (2). 2-Methyl-l,4,5,8-dimethano-l,2,3,4,4a,5,8,8a-octahydronaphthalene is commonly addressed as tetracyclododecene. Nadie anhydride introduces polar groups into the polymer. These polar groups promote adhesion. However, it has a greatly different polymerizability from that of a norbornene monomer having no polar group. Therefore, the copolymerization reaction does not sufficiently occur. Better results are obtained with tetracyclododecene instead of norbornene (3). Functionalized norbornenes are mostly modified in the 5-position. Substituents with ester groups or other donor groups, may slow down the rate of polymerization as they form chain propa41

42

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Table 2.1: M o n o m e r s for Cyclo Olefin C o p o l y m e r s Monomer

References

a-Olefin Ethene Propene 4-Methyl-l -pentene

(4) (4)

Cycloolefin Norbornene 5-Vinyl-2-norbornene 5-Methyl-2-norbornene 5-Ethylidene-2-norbornene Tetracyclododecene 2-Methyl-l,4,5,8-dimethano-l,2,3,4,4a,5,8,8aoctahydronaphthalene Dicyclopentadiene 5-Triethoxysilyl-2-norbornene Ethyltetracyclododecene 2-Methyltetracyclododecene-2-carboxylic acid methyl ester Nadie anhydride

k

7 2-"

\

■ ' ^ R

Norbc)rnene

f _ 7/

L·-Λ_

5-Vinyl- 2-norbornene

5-Ethylidene-2-norbornene

Dicyclopentadiene

Tetracyclododecene Figure 2.1: Monomers used for COCs

(5) (5) (4) (4) (5,6) (4) (2) (7) (8)

Cyclic Olefin Copolymers

43

(RO)

Figure 2.2: Polymerization of Cyclic Monomers (9-11). (RO) ROMP, (VA) Vinyl Addition Polymerization, (R/I) Radical/Ionic Polymerization gation through metal coordination. However, the use of substituted norbornenes increases the glass transition temperature considerably (12).

2.2 Polymerization and Fabrication Cyclic monomers can be polymerized by ROMP, ROMP followed by hydrogénation, or by copolymerization with ethylene and homogeneous polymerization, as shown in Figure 2.2. Each process results in a different type of polymer (10,13). A wide variety of organometallic catalysts useful for polymerization has been described (14). In the Norsorex process, norbornadiene is polymerized by a ROMP type process. Polymers synthesized by ROMP have poor thermal stability and oxidative stability due to unsaturation of the main chain. They are used as thermoplastic resins or thermosetting resins. The main chain of the polymer can be stabilized by hydrogénation. The process of hydrogénation of metathesis polymers and suitable catalysts have been described in detail (15). Although a polymer prepared by this method has improved oxidative stability, the thermal stability is reduced. In general, hydrogénation increases the glass transition temperature of a ROMP polymer by about 50°C, but because of the ethylene groups located

44

Engineering Thermoplastics: Polyolefins and Styrenics

between the cyclic monomers, the glass transition temperature is still low (9). The radical or ionic polymerization of norbornene yields a saturated polymer with a rearranged structure of 2,7 linkages (16). Polymerization using Ziegler-Natta catalysts yields a mostly saturated polymer with 2,3 linkages (17). The polymerization with heterogeneous Ziegler-Natta catalysts is accompanied by ROMP, whereas homogeneous metallocene, Ni, and Pd catalysts promote addition polymerization (18). The quasi living polymerization of ethene and norbornene has been reviewed, among other topics in living polymerization of alkenes (19). Specifically, arylimido-aryloxo-vanadium(V) complexes with methylaluminoxane or Et2AlCl as co-catalyst have been used as catalyst systems. The polymers exhibit a low polydispersity and a high molecular weight (20). In the vinyl addition polymerization, the bicyclic structural unit is left unchanged. Only the double bond is opened. The polymer obtained in this way does not contain double bonds. Poly(cycloalkene)s obtained from the vinyl addition polymerization method exhibit extremely high melting points. The high melting points make the polymers unprocessable. For this reason, comonomers, such as ethene or propene are introduced to lower the melting points. Copolymers of this type are addressed as COCs. Depending on the application, different demands are placed on the melt viscosity of the polymer. For injection molding applications, lower melt viscosities are required than for extrusion applications. For a given comonomer composition and processing temperature, the melt viscosity of the cycloolefin copolymers increases with the mean molecular weight. To lower the molecular weight, either hydrogen can be used as chain transfer agent or the polymerization temperature can be increased. In contrast, the molecular weight can only be increased by lowering the temperature (21). In addition, when 1-alkenes are used as comonomers, the molecular weights of the polymers tend to become low because the insertion reaction becomes slower and there occurs an additional chain transfer (22).

Cyclic Olefin Copolymers 2.2.1

45

Catalysts

Catalysts can be divided into three groups (10): 1. Metallocene catalysts, 2. Complexes of chromium, iron, cobalt and copper, and 3. Transition-metal nickel(II) and palladium(II) catalysts. Metallocene catalysts are most common. Complexes of chromium, iron, cobalt and copper are rarely used, as well as nickel and palladium catalysts. However, the latter class exhibits a high activity. A metallocene is a compound consisting of two cyclopentadienyl anions. The concept originates from ferrocene, and a metallocene is considered as a generalized ferrocene type. Metallocenes belong to the type of sandwich compounds. For industrial applications for the polymerization of norbornenes into COCs, zirconium based metallocene catalysts are most popular. However, other metal based catalysts have been described too. Catalysts for olefin polymerization have been reviewed in the literature (10,23,24). Certain types of metallocene compounds based on indenyl moieties are known as catalyst components for the polymerization of olefins (25,26). These compounds may also include a bis-cyclopentadienyl coordination complex with the transition metal. The two cyclopentadienyl groups are joined via a bridging group, such as an ethylene group, or a dimethyl-silanediyl group. In other types, two cyclopentadienyl groups are bridged by a single carbon atom. Common metallocene catalysts are summarized in Table 2.2. For example, ethylene bis(indenyl) zirconium dichloride can be prepared by the reaction of zirconium tetrachloride with bis(indenyl)ethane lithium salt in tetrahydrofuran (4). The synthesis of several other catalysts has been described in detail in the literature (25). An aluminoxane can be prepared by the reaction of Al2(S04)3 x I4H2O and trimethylaluminum in toluene at 0°C (4). The alumoxane acts as an activating co-catalyst to form an alkylmetallocene cation.

46

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Table 2.2: Metallocene Catalysts Compound

References

Ethylene bis(indenyl) zirconium dichloride Diphenylmethylene(cyclopentadienyl) (9-fluorenyl) zirconium dichloride Bis(indenyl) zirconium dichloride Methylene-bis(3-ferf-butyl-l-indenyl) zirconium dichloride Methylene-bis(3-ferf-butyl-l-indenyl) zirconium dichloride Methylene-bis(3-t-butyl-l-indenyl)hamium dichloride Cyclobutylidene(l-ry 5 -cyclopentadienyl)(l-r/ 5 -indenyl) zirconium dichloride Cyclopentylidene(l-r75-cyclopentadienyl)(l-775-indenyl) zirconium dichloride Cycloheptylidene(l-r75-cyclopentadienyl)(l-775-indenyl) zirconium dichloride Diphenylmethylidene(cyclopentadienyl)(9-fluorenyl) zirconium dichloride Cyclohexylidene(l-rj s -cyclopentadienyl)(l-rj 5 -indenyl) zirconium dichloride

(4) (5) (5) (25) (25) (25) (26) (26) (26) (26) (26)

Examples of alumoxanes suitable as activating co-catalysts in the catalysts system are methylalumoxane, isobutylalumoxane, 2,4,4trimethyl-pentylalumoxane, and 2-methyl-pentylalumoxane. Mixtures of different alumoxanes can also be used (25). Alumoxanes have a core structure analogous to boehmite, i.e., a sequence of - ( A l - O ) n - , either linear or also as rings. To the free valency of aluminum an organic group of halogen is attached. Alumoxanes are also addressed as aluminoxanes or alumina gels (27,28). On the other hand, instead of an alumoxane compound as activator, Ν,Ν-dimethylanilinium tetrakis-perfluorophenylboron has been used with a metallocene catalysts (29). Ruthenium complexes have been described that are active both in the ROMP reaction and in a subsequent hydrogénation step (30). These catalysts have the pyrimidin moiety incorporated, for example, ( 1,3-diisopropyltetrahydropyrimidin-2-ylidene) (ethoxymethylene) (tricyclohexylphosphine) ruthenium dichloride.

Cyclic Olefin Copolymers 2.2.2 Metallocene Catalyzed

47

Polymerization

Addition polymers of norbornene have been prepared using metallocene catalysts (31). An example of such a catalyst system is racemic isopropylene bis(l-indenyl) zirconium dichloride in combination with an aluminoxane (21). The reaction is carried out in hydrocarbon solvents, e.g., toluene. A solution of norbornene in toluene with the catalyst is degassed and then pressurized with ethene. The polymerization is carried out while stirring at 70°C under constant ethylene pressure at 18 bar. After completion, the polymer is precipitated in acetone and filtered (21). The cycloolefin copolymers obtained in this way have a high thermal shape stability and it is possible to use the polymers as thermoplastic molding compositions. In order to precipitate the polymer, conventionally, the polymer solution is mixed with a non-solvent or a polymer solution is poured into a non-solvent. If the polymer precipitates rapidly a fiber like precipitate having a low bulk density is obtained. In contrast, if the non-solvent is slowly added to the polymer solution the polymer precipitates slowly. As a result, uniform and spherical polymer particles having a bulk density are obtained (32). 2.2.2.3

Materials with high Glass Transition Temperature

Conventional processes for preparing COCs have some common problems. The conversion of the cycloolefin may be low and further, a high amount of ethylene incorporated results in unsatisfactory low glass transition temperatures. Catalyst compositions have been developed in order to obtain materials with high glass transition temperatures (26). Examples are shown in Table 2.3. These catalysts are used for the copolymerization of ethene and norbornene. The investigation of propylene and norbornene as comonomers is straightforward, since the respective copolymers have been expected to exhibit higher glass transition temperatures than the copolymers of ethene because of the higher glass transition temperature of propene in comparison to ethylene. A detailed investigation has been carried out, using various metallocene catalysts (33). However, the glass transition temperature

48

Engineering Thermoplastics: Polyolefins and Styrenics

Table 2.3: Materials with High Glass Transition Temperatures (26)

A: B: C: D: E:

Catalyst

Rings [No.]

A B C D E

4 5 7 0 6

Yield [g] 26.3 26.3 21.5 6.9 15.7

Activity [gg^h-1]

[°C]

2.1 x 105 2.1 x 105 1.7 x 105 0.5 x 105 1.3 X 105

289 288 286 216 288

Τχ

Cyclobutylidene(l-775-cyclopentadienyl)(l-i75-indenyl) zirconium dichloride Cyclopentylidene(l-f7 5 -cyclopentadienyl)(l-/f i -indenyl) zirconium dichloride Cycloheptylidene(l-f7 5 -cyclopentadienyl)(l-r/ 5 -indenyl) zirconium dichloride Diphenylmethylidene(cyclopentadienyl)(9-fluorenyl) zirconium dichloride Cyclohexylidene(l-rj 5 -cyclopentadienyl)(l-ij 5 -indenyl) zirconium dichloride

reported in this study, turned out to be somewhat lower than reported for ethene as comonomer using different catalysts (26). 2.2.2.2

Functionalization

COCs that contain cyclic poly(ene)s can be functionalized with maleic anhydride. These polymers do not have any gel particles and are completely soluble in decalin at 135°C, indicating that they are of substantially linear form and thus not crosslinked (4). 2.2.3 Addition

Polymerization

The representative metals constituting the addition polymerization catalyst include mostly Ni and Pd (34). Addition copolymers of cycloolefin compounds with a polar substituents in the side chain exhibit excellent heat resistance and transparency. They are also capable of crosslinking to improve the adhesion properties, the dimensional stability and the chemical resistance (35).

Cyclic Olefin Copolymers

49

A Ni based catalyst for addition polymerization can be prepared from nickel(2-ethylhexanoate), methylaluminoxane, and triethylborane (34). The polymerization is carried out in toluene as a solvent under pressure. Instead of methylaluminoxane, fluorina ted aromatic compounds, such as a, a, α-trifluorotoluene can be used (36). The polymerization yield may be deteriorated when the mole ratio is out of the range, i.e., the fluorine-containing aromatic hydrocarbon compound is used in an amount of less than one mole with respect to one mole of the nickel salt compound. Otherwise, when the fluorine-containing aromatic hydrocarbon compound is used in an amount of more than 100 moles with respect to one mole of the nickel salt compound, there occurs a discoloration of the product with a deterioration of efficiency in the aspect of economy. The introduction of functional groups is suitable to control the chemical and physical properties of the polymer. However, the introduction of functional groups may cause a reaction of the unshared electron pairs of the functional groups with the active catalytic sites. Thus, the active sites of the catalyst are destroyed. In order to overcome this problem, a procedure has been developed, where the functionalized monomers, such as maleic acid, nadie acid or their anhydrides are grafted after the polymerization reaction (4,37). Grafting takes place as a radical reaction, using e.g., dicumyl peroxide. Other attempts use excessive amounts of catalysts. Conventional Ziegler-Natta catalysts, compounds, such as TÍCI4 in combination with organoaluminum co-catalysts, have been used to prepare the addition polymer of norbornene (38). Carboxylic esters of norbornene can be polymerized with Pd(Il)-nitrile catalysts Pd(RCN) 4 x (BF4)2 with R = CH 3 ,C 2 H 5 (39). However, the polymerization takes place only selectively, as mostly the exo isomer polymerizes. Similarly, (r/ 3 -crotyl)(cycloocta-l,5-diene)palladium hexafluorophosphate can be activated with a with a co-catalyst such as AgBF4 or AgSbF 6 (40). On the other hand, special catalyst systems have been developed that allow the polymerization of norbornene-based monomers having an ester or acetyl group without loss of yield and molecular weight. Suitable ligands are introduced that avoid a deterioration

50

Engineering Thermoplastics: Polyolefins and Styrenics

of the catalytic activity. The stability of the catalyst system can be readily visualized in molecular models (9). For example, a homopolymer of norbornene carboxylic acid butyl ester can be prepared by addition polymerization using tricyclohexylphosphine and palladium(II) acetylacetonate as a catalyst (9). With regard to catalytic activity, a catalytic system comprising palladium(II) acetylacetonate or palladium(II) acetate, dimethylanilinium tetrakis(pentafluorophenylborate), and tricyclohexylphosphine is more effective than a catalyst system comprising (allyl Pd Clh, borate, and phosphine. It is believed that the acetylacetonate group is easily released from palladium to form a large space around the palladium, so a large norbornene monomer can access the site easily (9). Multi-component catalyst systems based on palladium compounds and phosphorus compounds show a particularly high activity (35). The high catalytic activity is not deteriorated in the course of polymerization. Substituted norbornene dérivâtes can be used that are otherwise difficult to polymerize. 2.2.4

Thermosetting

Resins

The majority of COCs use norbornene and ethene as comonomers. However, heat curable compositions have been described (41). These compositions find use in glass reinforced materials. They can be handled analogous to thermosetting resins, and thus the use of highly volatile comonomers, such as ethene or propene is prohibitive. Instead, other vinyl monomers are used. A heat curable formulation uses a mixture of tetracyclododecene, 2norbornene, 5-vinyl-2-norbornene, and divinylbenzene as reactive components (41). The mixture further contains 3,5-di-íerí-butylhydroxyanisole as antioxidant and a hybrid catalyst system containing a zirconium based metathesis catalyst and a radical catalyst. The metathesis catalyst is benzylidene (l,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)ruthenium dichloride and the radical catalyst is di-tert-butyl peroxide. In order to fabricate a resin laminated copper foil, the composition is poured over a glass cloth placed on a glass fiber reinforced poly(tetrafluoroethylene) (PTFE) film. Another sheet PTFE film is placed

Cyclic Olefin Copolymers

51

on the glass cloths, and the laminate is roller pressed to impregnate the glass cloths with the composition. The laminate in which the impregnated glass cloths are sandwiched between the PTFE films is then polymerized by adhering onto a hot plate heated at 145°C for 1 min. Thereafter, the PTFE films are peeled off to get a prepreg. Eventually the prepreg is laminated on both sides with a copper foil and a PTFE film having a thickness of 0.05 mm. The laminate is then put into a mold and heat pressed in the mold frame under a press pressure of 4.1 MPa at 200°C for 15 min. 2.2.5

Analysis

The comonomer content in COC can be determined with nuclear magnetic-resonance spectroscopy measurements. Other test methods include differential scanning calorimetry to investigate the glass transition temperature, gel permeation chromatography to get information about the molecular weight distribution, contact angle measurements to get the surface tension, and peel strength for the adhesion behavior (6,42). 2.2.6

Solvent Bonding

In particular for medical assemblies, the solvent bonding technique has been suggested. The method of solvent bonding includes the steps of (43,44): 1. Providing a first article of a polymer composition, 2. Providing a second article of a material of low crystallinity polymers, 3. Applying a solvent to one of the articles to define an interface area, and 4. Bonding the first article to the second article along the interface area. The first article may be a polymer composition with a COC as basic material. Suitable low crystallinity polymers to fabricate the second article include COCs and blends of COCs with poly(methyl pentene), other polyolefins, and styrenics.

52

Engineering Thermoplastics: Polyolefins and Styrenics

2.3

Properties

2.3.2

Mechanical

Properties

Typically COC has a higher modulus than high density polyethylene) (HDPE) or poly(propylene) (PP). Thus, it is the more brittle than ordinary poly(olefine)s. However, branched COC chains increase the flexibility and processability of the polymers without significantly weakening the optical properties (45). 2.3.2

Thermal Properties

The glass transition temperature varies with monomer composition. It can readily exceed 150°C. It increases with increasing norbornene content (22). A linear relationship between cyclic monomer content and glass transition temperature has been reported (6). 2.3.3

Optical Properties

Some COC types exhibit good optical properties. They exhibit high refractive indices. The highest refractive index among commercialized types is reported to be 1.54. In comparison, the refractive index of crown glass, a preferred type of optical glass used in lenses and other optical components is 1.52. Their transmittance is greater than 90%. Further, the low birefringence makes the materials ideal for opto-electrical applications. A birefringence comparable to poly(methyl methacrylate) (PMMA) can be achieved. For this reason, COCs are suitable as a glass substitute in any type of optical devices.

2.3.4 Barrier Properties The moisture barrier properties and humidity resistance make COCs suitable for container and film applications. The low moisture absorption prevents swelling.

Cyclic Olefin Copolymers

53

Table 2.4: Chemical Resistance of Apel™ (46) Chemicals Acid Alkaline Inorganic salt Alcohol Ketone Ester Chlorinated hydrocarbon Aromatics Hydrocarbons Gasoline Grease Salad oil Limonene

Apel

PP

PS

PVC

+ + + + + + —

+ + + + + +

+ + + / —

+ / + + —

—

/

/ -

/ + +

— + -

/ / / / + /

+: Resistant, /: Swells, -: Not resistant 2.3.5

Chemical

Resistance

In addition to moisture barrier properties, COCs exhibit good resistance to acid, alkalis and alcohols. Comparative chemical resistance properties are shown in Table 2.4. Important for medical applications, COC is considered as a high purity product with low amounts of low molecular weight extractable compounds.

2.4

Applications

There are numerous actual and potential applications for COC in the film, optical, medical, and packaging areas. 2.4.1

Films

COCs meet the optical application requirements as they can be used in the back light and image light areas of liquid crystalline displays (LCD)s, such as diffusion film, protective film, retardation film and as an anti-glare polarizing film for high resolution LCDs.

54

Engineering Thermoplastics: Polyolefins and Styrenics

2.4.2

Optical

Applications

Optical Applications include: • Pick-up lenses for digital versatile disc (DVD) players, recorder and super audio compact disc players, • Camera lenses for digital cameras and mobile phones, • Compact disks, • Optical films, • Lenses for laser printers, • Lenses for sensors, and • Films or sheets for the screens of laptop computers. 2.4.2.1

Crosslinked Types

Crosslinked products exhibit superior optical transparency, heat resistance, and adhesion, as well as improved dimensional stability, solvent resistance, and chemical resistance. In addition, crosslinking prevents the occurrence of cracks in films. Crosslinkable COCs are obtained by the modification with an alkoxysilyl group (2,47). A series of more or less complicated silyl modified norbornene dérivâtes have been described (48). As a side effect, the silyl group improves the adhesion properties of the materials. The crosslinkable COCs have been suggested for the use as alternatives for a glass substrate of a liquid crystal display devices and an electroluminescence (EL) display devices. Moreover, a crosslinkable COC can be used as a polarizing film, surface protective film, retardation film, transparent conductive film, light diffusion film, film for EL display devices, transparent conductive composite material, anti-reflection film, etc. Methods how to prepare these types of films have been described in detail (47). 2.4.2.2

Cuvette Cartridges

Disposable cuvette cartridges for optical measurements have been developed (49). The cartridge is formed from three flexible thin layers. The middle layer is an adhesive sheet with cut out regions, typically between 30 and 50, serving as optical chambers bounded

Cyclic Olefin Copolymers

55

by the two outer layers. Inlet and vent holes in one of the outer sheets provide access to the optical chambers. At least one of the outer sheets is made of a COC, since this material exhibits a low fluorescence. With its low background fluorescence, the cuvette cartridge is useful for high throughput fluorescence measurements of biological samples. 2.4.2.3

Toner Binder Resins

Toners find use in electrophotography (50). The basic invention of electrophotography originates from Carlson* and was filed in 1938 (51). The first commercial black and white copier, the Xerox A was released in 1949 and the first color copier was introduced in 1973. In reproducing a page by electrophotography, the following steps are involved (52): • Charging of the photoreceptor, • Exposure by an optical system to form the latent image, • Development, where the toner is contacted to the latent image, • Transfer where the toner is transferred to the paper, • Fusing where the toner is fixed on the surface of the paper, and • Cleaning. In color copiers or full-color printers, a silicone oil with satisfactory releasing properties is coated onto the fixing roller to prevent the so-called offset. That is, the toner adheres and accumulates on the fixing roller. However, this method requires an oil tank and an oil coating device, thus the device becomes complex and large. Oil-less type of image forming devices have been developed that do not use release oil in the fixing device. Instead of using release oil, a release agent like wax is added in large amounts within the toner formulation. Dry developers suitable for use in image forming devices are roughly classified into (53): 'Chester Floyd Carlson, born Feb. 8,1906 in Seattle, Washington, died Sep. 19, 1968

56

Engineering Thermoplastics: Polyolefins and Styrenics Table 2.5: Toner Formulations (53,54) Black White Toner (54)

%

Cyclic olefin resin Cyclized poly(isoprene) Carnauba Carbon black Charge controlling agent

60 25 15 10 1

Color Toner (53)

%

Topas® COC (binder resin) Poly(propylene) wax (release agent) Carnauba wax Boron complex (charge control agent) Quinacridone master batch (pigment)

76 5 2 2 12

1. Two-component developers in which toner is mixed with a carrier, such as ferrite powder, iron powder, glass beads, etc., 2. Magnetic single-component developers in which magnetic powder is comprised in the toner itself, and 3. Non-magnetic single-component developers. COCs have been used as binder resins in toners to replace the conventional binders, such as styrene/acrylate resins and poly(ester) resins (53,55). By using a COC, the softening point, melting point and dielectric property of the resultant toner can be satisfactorily controlled. Thereby the non-offset fixing temperature range of the toner can be expanded. In addition, the high speed fixability, the low-temperature fixability, and the low-pressure fixability can be also improved (54). Also, their excellent optical transparency makes these resins suitable for use in full-color toners (56). Typical formulations of oil-less toners utilizing COCs are shown in Table 2.5. The compatibility with other resins and the pigment dispersibility can be improved by introducing carboxyl groups into the COC by the fusing air oxidation method, maleic anhydride modification, or acrylic acid modification (53). Carnauba wax is obtained from the leaves of the carnauba palm. It is composed of esters of fatty acids and fatty alcohols. In contrast, a PP wax is unpolar. A toner including a large amount of wax tends

Cyclic Olefin Copolytners

57

to have a poor fluidity. However, when paraffin, polymerized olefin and microcrystalline wax are used together, the smoothness among toner particles is improved. 1-20% by weight of these waxes can improve smoothness among toner particles without exerting a bad influence on the wax and the toner (54). A charge control agent is added to impart polarity. Examples of charge control agents used for positive charge toners include quaternary ammonium salts or pyridinium salts. Examples of charge control agents used for negative charge toners include azo-based metal complexes, salicylic acid-based metal complexes, and boron complexes with diphenylglycolic acid dérivâtes. Coated fumed silica improves both the flow properties and the charging properties of the toner particle (55). 2.4.2.4

Data Storage Media

The combination of high transparency, high glass transition temperature, and refractive index, together with an excellent processability, makes COCs attractive as an alternative for materials like poly(carbonate) and PMMA in the field of optical components and high capacity DVDs and compact disks (57,58). For optical applications requiring extreme clarity it is desirable to minimize silver streaking, and yellowing. For example, Topas® 5013 can be modified pentaerythritol tetrastearate, pentaerythritol distearate, or zinc stéarate in order to improve the optical properties (59). These blends are suitable for high precision optical applications. 2.4.2.5 Photolithography Photoresists are photosensitive films used for the transfer of images onto a substrate (60). A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. Exposure to radiation provides a photoinduced reaction in the coating layer. After exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate. A photoresist can be either a positive or negative type. Mostly, in negative photoresists, areas that are exposed to the activating radi-

58

Engineering Thermoplastics: Polyolefins and Styrenics

Figure 2.3: Photoresist Polymers (Schematically) (61)

ation undergo polymerization or crosslinking reactions. Thus, the exposed material becomes insoluble. In contrast, in a positive photoresist, exposed portions are rendered more soluble in a developer solution while areas not exposed remain ideally insoluble (61). Basically, a positive resist composition consists of (62): 1. A resin which enhances a solubility of the resin in an alkaline developer by an action of an acid, and 2. A compound, which generates an acid upon irradiation. Polymers based on COCs that have been described for photoresists are schematically shown in Figure 2.3. In addition, to the formulation a photoacid generator, di-(4-ferf-butylphenyl)iodonium10-camphor sulfonate is added. Other optional additives include anti-striation agents, plasticizers, speed enhancers, etc. Ethyl lactate acts as a solvent (61). Several other types of photoacid generators have been described (62). The formulated resist composition is then spin coated on silicon wafers. The resist coating layer is exposed through a photomask at 193 nm, and then the exposed coating layers are post-exposure baked at 110°C. The coated wafers are then treated with a diluted aqueous tetramethylammonium hydroxide solution to develop the imaged resist layer and provide a relief image (61). 2.4.3 Medical

Applications

COC resins can be used in the development of precision medical

Cyclic Olefin Copolymers

59

instruments, where heat and moisture resistance and clarity are needed. Applications include: • • • • 2.4.4

Press through package sheets, Syringes, vials and bottles, Pre-filled syringes, and Surgical instruments. Packaging Areas

Packaging and multilayer barrier films produced from COC materials exhibit improved moisture and thermal resistance. Thus, they are suitable for • • • • 2.4.4.1

Pharmaceutical packagings, Blister packs, Food Packaging, and Extrusion Coated Packagings. Blister Packs

Multilayer sheets containing poly(chlorotrifluoroethylene) and COC for blister packaging applications have been described (63). In the production of the multilayered film, the fluoropolymer layer is joined with the thermoplastic polymer layer and an adhesive tie layer. The adhesive tie layer can be made up from 82% ethylene-based octene plastomer, 15% styrene modified terpene resin and 3% of a styrene/isoprene/styrene styrenic block copolymer. The multilayer film is formed by injection molding, co-injection blow molding, co-injection stretch-blow molding or co-extrusion blow molding techniques. 2.4.4.2

Heat Sealable Packaging Materials

Polymer-coated heat sealable packaging materials are composed of several layers (64). The material includes a fiber base of packaging paper or packaging board, an outer polymeric heat sealing layer, such as low density poly(ethylene) (LDPE), and an inner polymeric

60

Engineering Thermoplastics: Polyolefins and Styrenics

LDPE COC BOARD COC LDPE

Figure 2.4: Layers and Example for Packaging Article (64) water vapor barrier layer, which is partly or totally formed of an amorphous COC. In addition, further layers, e.g., polymeric oxygen barrier layers, such as ethylene vinyl alcohol or poly(amide) layers, can be incorporated into the packaging material. A most simple structure for the build up of the layers and an example for a packaging article are shown in Figure 2.4. The LDPE is generally used in the uppermost heat sealing layer and also gives protection against the permeation of water vapor. However, LDPE is not a very efficient material in this respect, and for achieving a good water vapor barrier it has to be used as a relatively thick layer. Alternatively, HDPE is used in fiber-based packaging materials as a considerably more efficient polymer water vapor barrier. The layer containing the HDPE is typically placed inside the packaging between the heat sealing layer and the fiber base and the possible oxygen barrier layer. It protects the base material and further layers from both environmental moisture and moisture emitted from the packed product. However, the drawback of the use of HDPE has been the curling of the material caused by it. The reason for this is the post-crystallization taking place in the HDPE layer after its extrusion. This problem can be circumvented by replacing the HDPE by COC. COCs exhibit good water vapor barrier properties, and in addition, they are amorphous. Thus, neither post-crystallization nor curling caused by this occur in the extruded COC layer (64). The barrier layer containing COC can be attached by extrusion directly to the heat sealing layer of LDPE. It is not necessary to

Cyclic Olefin Copolymers

61

apply a binding agent between the layers. COC as such is not heat sealable, but it can be heat sealed combined with LDPE. Further, the COC barrier layer can be attached directly to the base material. Eventually, the sealed package is formed by folding and heat sealing. The glass transition temperature Tg is an important parameter for the characterization of the material. Films with a Tg of 30-55°C can be heat sealed a low temperatures of 50-80°C (65). By varying the norbornene content in a copolymer with ethene as further comonomer, COCs of varying Tg can be prepared. Generally, reducing the norbornene content and increasing the ethylene correspondingly reduces the Tg. The following relationship has been reported (65):

Here N is the norbornene content in mol-% and Tg is the glass transition temperature in °C. Another research group reports quite similar relations (66). 2.4.4.3

Ultraclean Containers

Thermoplastic resin containers are used in various industrial fields because they are light in weight and can be mass produced. For example, containers made by injection molding of poly(styrene) (PS) resins, poly(ethylene terephthalate) (PET), or poly(ethylene) (PE) are used as cases for office supplies and consumers' goods, closed containers and, liquid beverages. In some uses of containers, their contents are very susceptible to contamination caused by the containers or the environment. For example, containers for storing and carrying wafers used for the production of semiconductors are required to effectively protect the wafers from external contamination substances such as water and chemical substances. Furthermore, the containers should not release contaminating substances. Semiconductor devices must be prevented from being spoiled with dust by all means because dust adherence of the dust coming from the air or treating chemicals to the surface of the devices causes reduction of yield and deterioration of performance.

62

Engineering Thermoplastics: Polyolefins and Styrenics

When chemical amplification type photoresists are stored after exposure, they are influenced in several minutes by basic organic substances contained in the environment in even a slight amount of less than about 10 ppb, and the desired resist patterns sometimes cannot be obtained. Therefore, containers used for storing and carrying these contents are required to exclude the outside contaminating substances. In addition, the containers themselves are required not to generate contamination substances. PS, PET, and PE as mentioned above, exhibit certain disadvantages in this aspect. On the other hand, since COCs are superior in transparency, heat resistance and chemical resistance, the use of them for various containers has been proposed (7). Molding materials comprising COCs can be polymerized from DCPD by ROMP using tungsten hexachloride, triethylaluminum and diisopropyl ether. The resulting polymer is hydrogenated by using a Ni-kieselguhr catalyst as a hydrogénation catalyst and activated alumina at 150°C. A molding material in the form of pellets can be obtained by mixing in a twin-screw extruder at 200°C and pelletizing. Instead of DCPD, ethyltetracyclododecene can be used. 2.4.4.4

Oxygen Scavenging Film

Many oxygen sensitive products, including food products, electronic components, pharmaceuticals, and medical products, deteriorate in the presence of oxygen. Both the color and the flavor of foods can be adversely affected. The oxidation of lipids within the food product can result in the development of rancidity. These products benefit from the use of oxygen scavengers in their packaging (67). One particular oxygen scavenger that has proved useful commercially is poly(ethylene/methyl acrylate/cyclohexene methyl acrylate). It has been found that COCs in a film structure having an oxygen scavenger offers a means for providing adequate interlaminar bond strength between the oxygen scavenger and adjacent layers, and good hot tack seals. 2.4.5 Absorption of Organic

Contaminants

To eliminate contaminants of soil or waters with organic compounds which occasionally or constantly enter the environment, such as oils,

Cyclic Olefin Copolymers

63

Table 2.6: Absorption of Oil by Cycloolefin Copolymers (68) No.

TK [°C]

Tm [°C]

Absorption [g Oil/g Polymer]

1 2 3 4

121 118 127 127

265 268 272 276

>10:1 >10:1 8:1 8:1

complete absorption and disposal of these contaminants is necessary. Polyolefins are suitable absorbents for absorbing oils on water surfaces. PP powder and granules as well as poly(norbornene) have been described as absorbents for hydrocarbons on water surfaces. It order to get a COC with a loose, wadding-like consistency, a solution of a COC in toluene is poured into the precipitating agent acetone in a ratio of about 1:10 at room temperature and the mixture is stirred at high speed for about 5 minutes (68). Experiments with various grades of COCs have been performed. The results are shown in Table 2.6. The results indicate that the capability of absorption decreases with glass transition temperature An ecological advantage is that the COC is unproblematic with respect to dumping and also combustion. Furthermore, reuse of the absorbent is possible, for example by simple extraction of the contaminants and subsequent drying (68). 2.4.6 Adhesives in Semiconductor

Technology

Adhesives for semiconductor parts have been developed. The compositions include COCs. The materials are either derived from ROMP and subsequent hydrogénation or from addition polymerization (69). The polymers are further modified by allyl alcohol, trimethoxyvinylsilane, allyl glycidyl ether, or maleic anhydride. The functionalization is effected by dicumyl peroxide. Other components in the composition include (69): • Fillers, either conductive or nonconductive, • Flame retardants,

64

Engineering Thermoplastics: Polyolefins and Styrenics

Figure 2.5: Bonding of a Conductive Film (69) • Low molecular weight resin, in order to improve the viscosity characteristics upon heating and melting of the base polymer, • Phenolic antioxidants, and • Fatty acid metal salts. From the composition, films are fabricated. The principle of bonding is illustrated in Figure 2.5. Here the joining of an adhesive bonding a tape carrier package, in which a semiconductor chip has been incorporated, to a liquid crystal display panel through an anisotropic conductive film is shown. The adhesive film is laminated onto the surface of the substrate, by placing a semiconductor part on the adhesive film, bonding the semiconductor part to the substrate by heating typically up to 190°C and pressurizing. Eventually, the adhesive film is cooled. Typically a bonding strength of 90-130 kp c m - 2 is obtained, which does not significantly alter its properties after 6 months. The adhesives are suitable for use in flip chip bonding of semiconductor parts. They exhibit good shelf stability, productivity, strength properties and heat resistance. The electrical properties, such as dielectric constant and dielectric loss tangent are highly satisfactory.

Cyclic Olefin Copolymers

65

Table 2.7: Examples for Commercially Available Cyclo Olefin Copolymers Tradename

Producer

Remarks

Apear® Apel™

Optical Polymers

Avatrel®

B.F. Goodrich (18) Mitsui Chemicals America, Inc. Promerus

Duvcor® 385

Promerus (18)

Duvcor® 387

Promerus (18)

Topas®

Polyplastics Co., Ltd. Topas Advanced Polymers, Inc.

Topas®

poly(norbornene) dielectric polymer tert-Butyl norbornenecarboxylate-norbornene5-methylenehexafluoroisopropanol copolymer 5-Norbornene-2-(2,2ditrifluoromethyl-2-hydroxy)ethyl homopolyTTlf*t* 11 l e i

Ethene norbornene copolymers Ethene norbornene copolymers

2.5 Suppliers and Commercial Grades Apel™, is obtained by Ziegler polymerization. It is available in film and resin form. The material exhibits a high density and a bulky structure. It is amorphous, optically isotropic and non polar (70). Topas® is copolymerized from norbornene and ethylene using a metallocene catalyst. Suppliers and Commercial Grades are shown in Table 2.7. Special grades are available for injection molding, extrusion, and toner production. Tradenames appearing in the references are shown in Table 2.8.

2.6

Safety

COCs are considered to be not harmful. However, they are inflammable.

66

Engineering Thermoplastics:

Tradename Description Aclon™ 1180

Polyolefins

and

Styrenics

Table 2.8: Tradenames in References Supplier Honeywell International Inc.

Poly(chlorotrifluoroethylene) (63) Affinity® Dow Metallocene catalyzed polymers (MCP), long chain LLDPE (63,67) Attane® Resins Dow Ultra low density poly(ethylene) (67) Dowlex® NG 5056E Dow 1-Octene/ethene copolymer (LLDPE) (67) Enerpar® Amoco Hydraulic oil (68) Engage™ resins DuPont Low density poly(ethylene) (67) Escorene® Exxon Ultra low density poly(ethylene) (67) Exact® Exxon Metallocene catalyzed ethylene copolymers (MCP) (67) Exceed® (Series) Exxon Linear low density poly(ethylene) (67) Glycolube® (Series) Lonza Inc. Fatty esters, flow promotor, mold release agent (59) Hefty® Pactiv Corp. Packages (67) Irgacure® 819 Ciba 2,2-Dimethoxy-2-phenyl acetophenone (67) Irgacure® 819 Ciba Bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide(67) Kevlar® DuPont Aramid (37) Ñuto® H Shell Anti-wear hydraulic oils (68) Silde-Rite® Pactiv Corp. Closure Systems (67) Surlyn® DuPont Ionomer resin (5)

Cyclic Olefin Copolymers

67

Table 2.8 (cont): Tradenames in References Tradename Supplier Description Sylvares® ZT105LT Arizona Chemical Comp. Styrene modified terpene resin (63) Tanner® Mitsui Chemicals, Inc. Ethylene/a-olefin copolymers (LLDPE) (67) Teflon® Dupont Tetrafluoro polymer (40) Topas® COC Topas Advanced Poylmers Cyclic olefin copolymers (49,59,63,65,67) Vector® Dexco Polymers LP Styrenic block copolymer (63) Vectra® (Series) Hoechst Celanese Corp. (Ticona) Liquid Crystal Polymer, composed from mainly 4-hydroxybenzoic acid or 6-hydroxy-2-naphthoic acid, further, depending on type: p-acetaminophenol, terephthalic acid, and biphenol (65) Zeonor® (Series) Nippon Zeon Co. Cyclo-olefin copolymer (49)

2.7 Environmental Impact and Recycling A route of chemical recycling by pyrolysis has been examined (71). The pyrolysis of COC was performed in a fluidized-bed reactor. Various parameters, such as pyrolysis temperature, fluidizing gas or residence time were varied. Under favorite conditions, the undesired tar fraction could be reduced to a minimum of around 10%. Up to 44% of valuable gases and 45% of aromatic light oils could be obtained at a pyrolysis temperature of 700°C. In general, norbornene was recovered only in traces. Thus, it is concluded that 2-norbornene is not sufficiently stable to resist the conditions of pyrolysis. Actually, a retro-Alder reaction occurs resulting in ethene and cyclopentadiene.

References 1. W.A. Anderson and G.N. Merckling, Polymeric bicyclo-(2,2,l)-2heptene, US Patent 2 721189, assigned to Du Pont, October 18,1955.

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Engineering Thermoplastics:

Polyolefins

and

Styrenics

2. N. Oshima, Y. Maruyama, N. Sakabe, K. Sawada, K. Ohkita, Y. Hashiguchi, T. Kanamori, and K. Kawahara, Composition of cyclic olefin addition copolymer and cross-linked material, US Patent 6 639 021, assigned to JSR Corporation (Tokyo, JP), October 28, 2003. 3. M. Sakamoto and Y. Tsunogae, Copolymer formed by ring-opening polymerization, product of hydrogénation of copolymer formed by ring-opening polymerization, and process for producing these, US Patent 6 815 516, assigned to Zeon Corporation (Tokyo, JP), November 9, 2004. 4. N. Ishimaru, T. Tsutsui, A. Toyota, and N. Kashiwa, Cyclo-olefinic random copolymer, olefinic random copolymer, and process for producing cyclo-olefinic random copolymers, US Patent 5 008 356, assigned to Mitsui Petrochemical Industries, Ltd. (Tokyo, JP), April 16,1991. 5. W. Kreuder and F. Osan, Cycloolefin copolymers and processes for their preparation, US Patent 5 756 623, assigned to Hoechst AG (DE) and Mitsui Petrochemical Ltd. (JP), May 26,1998. 6. J.Y. Shin, J.Y. Park, C. Liu, J. He, and S.C. Kim, Chemical structure and physical properties of cyclic olefin copolymers, Pure Appl. Chem., 77 (5):801-814, May 2005. 7. K. Otoi and T. Suzuki, Contamination resistant cyclic olefin container, US Patent 6682797, assigned to Nippon Zeon Co., Ltd. (Tokyo, JP), January 27,2004. 8. K. Ohkita, T. Imamura, and N. Oshima, Cycloolefin copolymer formed by ring-opening polymerization, process for producing the same, and optical material, US Patent 7056999, assigned to JSR Corporation (Tokyo, JP), June 6, 2006. 9. S.-H. Chun, W.-K. Kim, S.-C. Yoon, T.-S. Lim, H. Kim, and K.-H. Kim, Method for preparing norbornene based addition polymer containing ester or acetyl functional group, US Patent 7312285, assigned to LG Chem, Ltd. (KR), December 25, 2007. 10. F Blank and C. Janiak, Metal catalysts for the vinyl/addition polymerization of norbornene, Coord. Chem. Rev., 253(7-8):827-861, April 2009. 11. R. Shick, Commercializing poly cyclic polyolefins, Technical report, Promerus, Brecksville, OH, 2008. [electronic:] www.promerus. com/ASSETS/0CB6C4C4B40048B3B6FA217F063D8A67/Technology% 20Tuturial%205-27-08%20Update%20(2).pdf. 12. T. Hasan, T. Ikeda, and T. Shiono, Homo- and copolymerization of norbornene derivatives with ethene by ansa-fluorenylamidodimethyltitanium activated with methylaluminoxane, /. Polym. Sei., Part A: Polym. Chem., 45(20):4581-4587, October 2007. 13. I. Tritto, L. Boggioni, and D.R. Ferro, Metallocene catalyzed etheneand propene co-norbornene polymerization: Mechanisms from a de-

Cyclic Olefin Copolymers

14. 15. 16. 17. 18.

19. 20.

21. 22.

23. 24. 25.

26.

69

tailed microstructural analysis, Coord. Chem. Rev., 250(1-2):212-241, January 2006. X. Li and Z. Hou, Organometallic catalysts for copolymerization of cyclic olefins, Coord. Chem. Rev., 252(15-17):1842-1869, August 2008. T. Sunaga, M. Okita, and T. Asanuma, Preparation of hydrogenated product of cyclic olefin ring-opening metathesis polymer, US Patent 6197894, assigned to Mitsui Chemicals, Inc. (JP), March 6, 2001. N.G. Gaylord, A.B. Deshpande, B.M. Mandai, and M. Martan, Poly2,3- and 2,7-bicyclo[2.2.1]hept-2-enes: Preparation and structures of polynorbornenes, /. Macromol. Sci.-Chem., 11(5):1053 -1070, May 1977. N.G. Gaylord and A.B. Deshpande, Structure of vinyl-type polynorbornenes prepared with Ziegler-Natta catalysts, /. Polym. Sei, Polym. Lett. Ed., 14:613-617, October 1976. W Kaminsky and M. Arndt-Rosenau, "Tactic norbornene homo- and copolymers made with early and late transition metal catalysts," in L.S. Baugh and J.A.M. Canich, eds., Stereoselective Polymerization with Single-Site Catalysts, chapter 16, pp. 413-444. CRC Press, Boca Raton, FL, 2008. GJ. Domski, J.M. Rose, G.W. Coates, A.D. Bolig, and M. Brookhart, Living alkene polymerization: New methods for the precision synthesis of polyolefins, Prog. Polym. Sei., 32(l):30-92, January 2007. W. Wang and K. Nomura, Remarkable effects of aluminum cocatalyst and comonomer in ethylene copolymerizations catalyzed by (arylimido)(aryloxo) vanadium complexes: efficient synthesis of high molecular weight ethylene/norbornene copolymer, Macromolecules, 38(14): 5905-5913, July 2005. T. Weller, F. Osan, F. Kuber, and M. Aulbach, Process for preparing cycloolefin copolymers, US Patent 5 698 645, assigned to Hoechst Aktiengesellschaft (Frankfurt, DE), December 16,1997. G.M. Benedikt, E. Elce, B.L. Goodall, H.A. Kalamarides, L.H. Mclntosh, L.F. Rhodes, K. Selvy, C. Andes, K. Oyler, and A. Sen, Copolymerization of ethene with norbornene derivatives using neutral nickel catalysts, Macromolecules, 35(24):8978-8988, November 2002. G.G. Hlatky, Heterogeneous single-site catalysts for olefin polymerization, Chem. Rev., 100(4):1347-76,2000. G.G. Hlatky, Single-site catalysts for olefin polymerization: Annual review for 1997, Coord. Chem. Rev., 199(l):235-329, April 2000. L. Resconi, D. Balboni, V.A. Dang, and L.-C. Yu, Metallocene compounds and their use in catalysts for the polymerization of olefins, US Patent 6268518, assigned to Montell Technology Company B.V. (NL), July 31,2001. J.-C. Tsai, M.-Y. Wu, T.-Y. Hsieh, Y.-Y. Wei, and C.-Y Yu, Catalyst composition for preparing olefin polymers, US Patent 6930157, assigned

70

Engineering Thermoplastics:

Polyolefins

and

Styrenics

to Industrial Technology Research Institute (TW), August 16,2005. 27. A.R. Barron, Oxide, chalcogenide and related clusters of aluminum, gallium and indium, Comments Inorg. Chem., 14(2):123-153,1993. 28. A.R. Barron, Commercialization of alumoxane nanoparticles, [electronic:] http://www.nanotxstate.org/resources/barronnac31oct2005. pdf, 2005. 29. B.A. Harrington, Copolymerization process for the preparation of crystalline copolymers of olefins and cyclic olefins, US Patent 5 621054, assigned to Exxon Chemical Patents Inc. (Wilmington, DE), April 15, 1997. 30. M. Sakamoto, S. Okada, Y. Tsunogae, S. Ikeda, W.A. Herrmann, and K. Oefele, Ruthenium complexes, process for preparation thereof, and processes for producing open-ring polymer of cycloolefins and hydrogénation products thereof by using the complex as catalyst, US Patent 7084 222, assigned to Zeon Corporation (Tokyo, JP), August 1,2006. 31. W. Kaminsky, A. Bark, and M. Arndt, New polymers by homogeneous zirconocene/aluminoxane catalysts, Makromol. Chem., Macromol. Symp., 47:83-93,1991. 32. C.-H. Choi, S.-Y. Kim, and J.-U. Choi, Method for preparing cyclic olefin polymer having high bulk density and cyclic olefin polymer prepared thereby, US Patent 7202312, assigned to LG Chem, Ltd. (Seoul, KR), April 10, 2007. 33. W. Kaminsky, S. Derlin, and M. Hoff, Copolymerization of propylene and norbornene with different metallocene catalysts, Polymer, 48(25): 7271-7278, November 2007. 34. Y.C. Jang and H.K. Sung, Method for preparing homo-and co-polymers of cyclic olefin compounds using an organic boron compound as a catalyst activator, US Patent 7 091290, assigned to Korea Kumho Petrochemical Co., Ltd. (Seoul, KR), August 15, 2006. 35. N. Oshima, M. Kaizu, S. Ebata, and T. Imamura, Process for producing cycloolefin addition polymer, US Patent 7268196, assigned to JSR Corporation (Tokyo, JP), September 11, 2007. 36. Y.C. Jang and H.K. Sung, Method for preparing a homo-and co-polymers by polymerization of cyclic olefin compounds using fluorinecontaining aromatic hydrocarbon compound as catalyst activator, US Patent 6998450, assigned to Korea Kumho Petrochemical Co., Ltd. (Seoul, KR), February 14,2006. 37. S. Minami, H. Kajiura, H. Oda, and H. Yamaguchi, Random copolymer, and process for production thereof, US Patent 5179171, assigned to Mitsui Petrochemical Industries, Ltd. (Tokyo, JP), January 12,1993. 38. J.E. McKeon and P.S. Starcher, Novel polynorbomenes, process for production thereof, and products produced therefrom, US Patent 3330815, assigned to Union Carbide Corp, July 11,1967.

Cyclic Olefin Copolymers

71

39. J.P. Mathew, A. Reinmuth, J. Melia, N. Swords, and W. Risse, (77-3-allyl) palladium (ii) and palladium (ii) nitrile catalysts for the addition polymerization of norbornene derivatives with functional groups, Macromolecules, 29(8):2755-2763,1996. 40. B.L. Goodall, W. Risse, and J.P. Mathew, Addition polymers of polycycloolefins containing functional substituents, US Patent 5 705 503, January 6,1998. 41. T. Sugawara and H. Tanimoto, Polymerizable composition and molded articles produced by using the same, US Patent 7381 782, assigned to Zeon Corporation (Tokyo, JP), June 3, 2008. 42. G.M. Benedikt, B.L. Goodall, N.S. Marchant, and L.F. Rhodes, Polymerization of multicyclic monomers using zirconocene catalysts. Effect of polymer microstructure on thermal properties, New J. Chent., 18 (1):105-114,1994. 43. Y.-p.S. Ding, B. Lai, M.T.K. Ling, R. Mennenoh, D. Beedon, L. Woo, S. Corbin, G. Dillon, D. Pennington, C. Qin, and P. Ryan, Cycloolefin blends and method for solvent bonding polyolefins, US Patent 6 590 033, assigned to Baxter International Inc. (Deerfield, IL), July 8, 2003. 44. Y.-p.S. Ding, C. Qin, L. Woo, and M.T.K. Ling, Method for solvent bonding polyolefins, US Patent 6632318, assigned to Baxter International Inc. (Deerfield, IL), October 14, 2003. 45. J. Katajisto, M. Linnolahti, and T.A. Pakkanen, Effect of branching of cyclo-olefin copolymers and polycarbonate polymers on mechanical and optical properties: Ab initio and molecular simulation study, /. Mol. Struct., 758(2-3):189-194, 2006. 46. Mitsui Chemicals, Cyclo olefin copolymer characteristics, [electronic:] http ://www.mitsuichemicals .com/apel_cha .htm, 2008. 47. N. Oshima, Y. Maruyama, M. Kaizu, K. Sawada, T. Hayashi, and K. Ohkita, Cyclic olefin addition copolymer and process for producing same, crosslinking composition, crosslinked product and process for producing same, and optically transparent material and application thereof, US Patent 6992154, assigned to JSR Corporation (Tokyo, JP), January 31, 2006. 48. N. Oshima, T. Sakai, K. Ohkita, and T. Tsubouchi, Cycloolefin addition copolymer and optical transparent material, US Patent 7015293, assigned to JSR Corporation (Tokyo, JP), March 21, 2006. 49. L.J. Dietz and C.E. Todd, Disposable optical cuvette cartridge with low fluorescence material, US Patent 7 259 845, assigned to PPD Biomarker Discovery Sciences LLC (Wilmington, NC), August 21,2007. 50. B.E. Springett, "A brief introduction to electrophotography," in A.S. Diamond and D. Weiss, eds., Handbook of Imaging Materials, chapter 4, pp. 145-172. Marcel-Dekker, Inc., New York, 2nd edition, 2001.

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Engineering Thermoplastics:

Polyolefins

and

Styrenics

51. C.F. Carlson, Electron photography, US Patent 2221776, November 19,1940. 52. P.C. Juien and R.J. Gruber, "Dry toner technology," in A.S. Diamond and D. Weiss, eds., Handbook of Imaging Materials, chapter 5, pp. 173208. Marcel-Dekker, Inc., New York, 2nd edition, 2001. 53. Y. Suwa and T. Nakamura, Full-color toner for oil-less fixing, US Patent 6846602, assigned to Tomoegawa Paper Co., Ltd. (Tokyo, JP) and Ticona GmbH (DE), January 25, 2005. 54. K. Tomita and N. Iwata, Oilless toner, US Patent 7309553, assigned to Ricoh Company Limited (Tokyo, JP), December 18, 2007. 55. W.-S. Lee, C.-S. Lee, H.-E. Han, and K.-H. Song, Non-magnetic monocomponent positive toner composition having superior transfer efficiency, US Patent 7378206, assigned to LG Chem, Ltd. (KR), May 27, 2008. 56. Y. Suwa and T. Nakamura, Toner for electrophotography and method for forming image using the same, US Patent 7 378 209, assigned to Tomoegawa Paper Co., Ltd. (Tokyo, JP) and Ticona GmbH (Kelsterbach, DE), May 27, 2008. 57. R.R. Lamonte and D. McNally, Cyclic olefin copolymers, Adv. Mater. Processes, 159(3):33-36, 2001. 58. J. Kiesewetter, B. Arikan, and W. Kaminsky, Copolymerization of ethene with norbornene using palladium(II) a-diimine catalysts: Influence of feed composition, polymerization temperature, and ligand structure on copolymer properties and microstructure, Polymer, 47 (10):3302-3314, May 2006. 59. D.A. Hammond and D. Heukelbach, Cycloolefin copolymer resins having improved optical properties, US Patent 6 951898, assigned to Ticona LLC (Summit, NJ), October 4,2005. 60. W.M. Moreau, Semiconductor Lithography: Principles, Practices, and Materials, Microdevices, Plenum Press, New York, 3rd edition, 1991. 61. G.G. Barclay, S.J. Caporale, W. Yueh, Z. Mao, and J. Mattia, Copolymers and photoresist compositions comprising same, US Patent 6849381, assigned to Shipley Company, L.L.C. (Marlborough, MA), February 1, 2005. 62. K. Kodama and H. Kanda, Positive resist composition for immersion exposure and method of pattern formation with the same, US Patent 7 273 690, assigned to Fujifilm Corporation (Tokyo, JP), September 25, 2007. 63. S. Rhee and M.P Delia Vecchia, Formation of multilayer sheets containing PCTFE and COC for blister packaging applications, US Patent 7211308, assigned to Honeywell International Inc. (Morristown, NJ), May 1, 2007.

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73

64. T. Penttinen, K. Nevalainen, and J. Jarvinen, Method for manufacturing heat-sealable packaging material having barrier layer; containing cycloolefin copolymer, US Patent 7 344 759, assigned to Stora Enso Oyj (Helsinki, FI), March 18, 2008. 65. R.D. Jester, Cycloolefin copolymer heat sealable films, US Patent 7288316, assigned to Topas Advanced Polymers, Inc. (Florence, KY), October 30, 2007. 66. M.-J. Young, W.-S. Chang, and C.-C.M. Ma, Polymerization kinetics and modeling of a metallocene cyclic olefin copolymer system, Eur. Polym. /., 39(1):165-171, January 2003. 67. J.W. Rivett and D.V. Speer, Oxygen scavenging film with cyclic olefin copolymer, US Patent 7258930, assigned to Cryovac, Inc. (Duncan, SC), August 21, 2007. 68. F. Helmer-Metzmann and A. Jacobs, Method for absorbing contaminants, US Patent 6818 590, assigned to Ticona GmbH (DE), November 16, 2004. 69. J. Kodemura, Adhesive for semiconductor part, US Patent 6833180, assigned to Nippon Zeon Company, Ltd. (Tokyo, JP), December 21, 2004. 70. Mitsui Chemicals, Apel™ cyclo olefin copolymer (COC), [electronic:] http://www.mitsuichemicals.com/apel.htm, 2008. 71. M. Donner and W. Kaminsky, Chemical recycling of cycloolefin-copolymers (COC) in a fluidized-bed reactor, /. Anal. Appl. Pyrolysis, 74 (l-2):238-244, August 2005.

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3

Ultra High Molecular Weight Poly(ethylene) Ultra high molecular weight poly(ethylene)s (UHMWPE)s are a special form of poly(ethylene) (PE). Due to the exceptional properties in comparison to ordinary PE types, UHMWPEs deserve to be dealt with in a separate chapter. The polymerization of UHMWPE was commercialized in the 1955 by Ruhrchemie AG (l).

3.1

Monomers

The essential and only monomer for UHMWPE per definition is ethene, also addressed as ethylene. However, this should not taken too seriously. In special cases, some other comonomers are used. Initially, ethylene was obtained by the dehydration reaction of ethanol. Nowadays, ethylene is obtained by steam cracking from naphtha as a basic chemical. Steam cracking degrades longer aliphatic chains and introduces the double bond. Steam cracking is done at temperatures up to 900°C and leaves a wide variety of products behind. Ethylene is recovered by distillation processes. The production of ethylene by gas crackers, mostly from C2, C3, and some C4 feeds, amounts to about 40% of the world ethylene capacity. This results in a small coproduction of benzene compared to benzene co-produced in naphtha and gas oil crackers, which account for 60% of the world's ethylene production capacity. A typical overall benzene yield from ethane cracking is on the order of only 0.6% of the ethane feed, and the yield of benzene from propane cracking is on the order of 3% of the propane feed. In contrast, the 75

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Engineering Thermoplastics: Polyolefins and Styrenics

yield of benzene resulting from naphtha cracking can range from 4 -10% of the naphtha feed depending the on aromatic content of the naphtha and the severity of cracking (2).

3.2 Polymerization and Fabrication Various types of catalysts have been described, including ZieglerNatta catalysts, mixed catalysts and single-site catalysts. These types are explained in detail subsequently. 3.2.1 Ziegler-Natta

Catalysts

Traditionally, UHMWPE is produced by Ziegler-Natta polymerization. This process requires exceptionally pure ethylene and other raw materials. The low-pressure polymerization of olefins using Ziegler-Natta catalysts, i.e., mixtures of compounds of transition groups IV to VI of the periodic table of the elements together with organometallic compounds of groups I to III is widely applied. Such catalysts, consist of titanium alkyl compounds and aluminum alkyl compounds or alkylaluminum halides. The Ziegler-Natta catalysts are prepared by the reduction of TiIV compounds, e.g., T1CI4 or esters of titanic acid, by organoaluminum compounds. A higher catalyst activity and thus an improved polymer color is achieved by the use of MgCh as support component. If the polymerization is carried out in suspension, agglomeration of the polymer particles formed and settling as a deposit on the walls of the reactor is frequently observed. Such phenomena are undesirable, since they adversely affect heat transfer and thus the possible throughput. In addition, the agglomerates can grow until they are relatively large, so that the output of product is adversely affected (3). Further, thé polymerization plant has to be frequently shut down and cleaned. The probability of the formation of polymer agglomerates is appreciably increased by electrostatic interactions. This phenomenon is, inter alia, also known in the handling of polymer powders. Owing to the fact that the polymer particles are not electrically conductive, electrostatic charging occurs in pneumatic transport systems in an

Ultra High Molecular Weight Poly(ethylene)

77

electrically nonconductive environment, and this can lead to wall deposits and finally to blockages. A similar occurrence is to be expected in polymerization processes. The polymeric particles move quickly in a nonconductive medium, e.g., the monomer in the gas or liquid phase or an aliphatic hydrocarbon, and become charged as a result. The polymer agglomerates and polymer deposits on the reactor walls are consequently observed. The immobilized polymer particles grow to form a firmly adhering coating on the reactor wall, and this significantly impairs a heat transfer. This coating has to be removed mechanically from the empty reactor (4). In order to increase in the electrical conductivity of the hydrocarbon, protic compounds, which are soluble in the hydrocarbon, for instance, poly(amine)s are added (3). In concentrations of around 30 ppm, the catalyst activity is not affected. A catalyst, prepared from isoprenylaluminum and titanium tetrachloride has been used to prepare polymers with a highly irregular shape (5). The polymerization is performed at 70-80°C with an ethylene partial pressure of 0.16-0.27 M Pa. A bulk density of 0.16-0.23 g e m - 3 is obtained. Such materials are intended to be used as filter elements. 3.2.1.1 Multiple Zone Process In the multiple zone process an olefin mixture is polymerized in a first reaction zone to produce a pre-polymer that has a lower molecular weight up to 35-65% the final conversion. After this step, volatile materials, such as hydrogen, are removed. The polymerization continues in a second reaction zone by adding more of the olefin mixture to produce the final polymer with a higher molecular weight (6). Both reaction zones use a Ziegler-Natta catalyst. The total amount of the required catalyst can be added in the first reaction zone and then carried over to the later reaction zone or zones. Alternatively, an additional amount of catalyst can be added in the second reaction zone. Common Ziegler-Natta catalysts are used. The resulting polymer has a bimodal molecular weight distribution containing a high molecular weight component and a low molecular weight component. The high molecular weight component imparts a supe-

78

Engineering Thermoplastics: Polyolefins and Styrenics

rior bubble stability in a blown film process and the low molecular weight component imparts excellent processability. 3.2.2

Mixed

Catalysts

Mixed catalysts have the titanium in the oxidation states four and three together with an organic aluminum compound. The molar ratio of TiIV to Ti m is preferably 2.6:1 (4). Such a catalyst, preactivated with triethylaluminum exhibits a low tendency to form deposits. Other catalyst systems are based on organic zirconium or hafnium compounds. One of the most economical routes to most commercial grades of olefin polymers is the loop slurry process with a paraffin diluent. This process was introduced by Chevron Phillips in 1960 (7). There, a mixture of catalyst particles, growing polymer particles, comonomers, and diluent is pumped in a loop. The polymer particles are harvested by guiding a side stream of the slurry to settling chambers, where the polymer particles settle toward the bottom. The polymerization process can be carried out at a temperature low enough that the resulting polymer is largely insoluble in the diluent. The pressures in the loop slurry process are in the range of 2.5-4 M Pa. Alkyl compounds of Group IVB metals can readily eliminate a hydrogen through a mechanism referred to as ß-hydride elimination (8), as shown in Eq. 3.1. M - C H 2 - C H 2 - R -> M - H + CH 2 =CH-R.

(3.1)

^-Stabilized compounds are inherently more stable then those compounds, which contain ^-hydrogens. Therefore, catalysts where the j3-positions are blocked, are preferred (8). Examples are zirconium tetrakis(trimethylsilylmethyl) or hafnium tetrakis(trimethylsilylmethyl). Catalyst supports are porous alumina with an amount of 0.5% of silica. Properties of polymers obtained with supported zirconium tetrakis(trimethylsilylmethyl) catalyst systems are shown in Table 3.1. The incorporation of 1-hexene lowers the molecular weight of the resultant polymer.

Ultra High Molecular Weight Poly(ethylene)

79

Table 3.1: Properties of Polymers (8) T/[°C]

P/[MPa]

l-Hexene/[g]

p/[gcm 3 ]

TS a /[MPa]

SAb/tg]

90 90 90 75 75

3.8 3.8 3.8 25.9 25.9

0 20 60 0 60

0.929 0.930 0.927 0.930 0.927

45.3 56.5 64.4 65.4 58.8

64 62 75 75 61

Catalyst: Zirconium tetrakis(trimethylsilylmethyl) a TS: Tensile strength b SA: Sand wheel abrasion Single-Site

3.2.3

Catalysts

Unlike the conventional UHMWPE made with the Ziegler catalysts, the single-site UHMWPE has narrow molecular weight distribution. A suitable catalyst is supported 8-quinolinoxytitanium trichloride and triethylaluminum. The supported catalyst is prepared by (9): 1. 2. 3. 4.

Treating a silica support with hexamethyldisilazane, Calcining the treated silica, Treating the calcined silica with dibutylmagnesium Mixing the treated silica with 8-quinolinoxytitanium trichloride, and 5. Removing any solvents. The polymerization is performed at a temperature of 50-80° C at a pressure of 3.5-14 M Pa. At higher pressures, the process is more productive. Using an aromatic solvent reduces the molecular weight of the polymer considerably. Thus, isobutane is the preferred solvent. This process has a high catalyst activity of 1,200 k g m o l ^ h - 1 . It produces UHMWPE with improved tensile properties and impact resistance. The molecular weight is greater than 4.5 M Dalton and the polydispersity is less than 3. In contrast, the unsupported catalyst has an activity of only 600 kg m o l ^ b r 1 , however large molecular weights are reached as well. In the case of supported 8-quinolinoxytitanium tribenzyl, but omitting the treatment of silica with dibutylmagnesium, a still higher

80

Engineering Thermoplastics: Polyolefins and Styrenics

catalytic activity is obtained of 26,000 k g m o l ^ h 1 . The molecular weight is 5.3 MDalton and the polydispersity is 2.6 (9). The presence of an organophilic clay increases the catalyst activity (10). Suitable clays include montmorillonite, hectorite, mica, etc. For example, Lucentite™ is a trioctylmonomethylammonium salttreated synthetic hectorite. The clays are modified with quaternary ammonium compounds. The clays are heat treated prior to their use in the polymerization process. Further, the incorporated clay can improve the performance of the UHMWPE or function as filler. 3.2.4

Fractionation

PE fractions can be produced with a polydispersity of less than 2.3 and a weight-average molecular weight (Mw) of greater than 1-6 MDalton (11). Such PE fractions are separated from an UHMWPE parent polymer by first dissolving the parent polymer in a relatively good solvent to form a PE parent solution. The conditions employed for such dissolution are selected to reduce the degradation of the UHMWPE parent polymer. In particular, the UHMWPE parent polymer and the solvent may be agitated at a rate of 55-65 rpm while heating the mixture at a temperature ranging from about the melting point temperature of the UHMWPE parent polymer to about 30°C above its melting point temperature. This agitation and heating of the mixture may be performed for a period of time effective to dissolve substantially all of the UHMWPE parent polymer in the solvent. After this dissolution step, the resulting parent solution is then transported into a fractionation column in which a support, e.g., glass beads, is disposed. The fractionation column may be scaled-up in size to produce relatively large quantities of the PE fractions. The fractionation column is operated at conditions effective to form a precipitate on the support. The temperature of the column is lowered to a temperature less than about 40°C at a rate of 1-0.5K hr" 1 . The PE fractions may then be recovered from the fractionation column by displacing a recovery solvent/non-solvent mixture into the column. The relative concentrations of the solvent and the nonsolvent are based on a solvent gradient profile of the PE parent polymer. The temperature of the column is raised to a temperature ranging from about the melting point temperature of the UHMWPE

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parent polymer to about 30°C above its melting point temperature, thereby heating the solvent/non-solvent mixture. The fractionation column is maintained at that temperature while a portion of the poly(ethylene) parent polymer is allowed to dissolve in the solvent/ non-solvent mixture. The mixture subsequently can be displaced from the fractionation column and combined with a precipitating agent to recover the poly(ethylene) fraction dissolved therein. The foregoing steps related to the recovery of the poly(ethylene) fractions can be repeated until the solvent/non-solvent mixture exiting the fractionation column is substantially absent of the poly(ethylene) precipitate. 3.2.5

Crosslinking

UHMWPE components are known to undergo a spontaneous, postfabrication increase in crystallinity and changes in other physical properties. These changes may occur in medical parts after sterilization with gamma radiation, which initiates an ongoing process of chain scission, crosslinking, and oxidation or peroxidation involving the free radicals formed by the irradiation. These degradative changes may be accelerated by oxidative attack and cyclic stresses applied during use (12). 3.2.6

Fabrication

Fabrication techniques include compaction and sintering, direct compression molding, hot stamping, forging, and hot plate or spin welding (13). Articles formed from UHMWPE polymers can be prepared in a one step process by using high temperature compression, or in a two step process comprising cold compaction molding followed by high temperature compression molding. During high temperature compression molding, the polymeric powder is poured into a positive pressure mold that is heated and then cooled under pressure. The cooled mold is then opened to yield a fully sintered UHMWPE article. In order to reduce the potential for corrosion, chlorine/acid acceptors or scavengers are generally added in low levels, typically in the range of 0.01-5.00%, to the dry polymer during polymerization

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Engineering Thermoplastics: Polyolefins and Styrenics Table 3.2: Properties of an UHMWPE Type 3 Property Density Tensile Modulus Tensile Stress (Yield) Tensile Strain (Yield) Charpy notched impact strength 23°C Charpy notched impact strength -30°C Vicat Softening Temperature a GUR™ UHMW-PE 5113, Ticona

Value

Unit

0.93 g cm"3 750 MPa 17.0 MPa 20 % >100 kj m~2 >100 kirn -2 80 °C

or after formation. Most common are metal soaps, such as calcium stéarate and zinc stéarate. In addition to serving as acid scavengers, stéarates also function as internal lubricants and as mold release agents. However, these compounds lower the cold compaction strength of molded articles (14). This effect is less dominant, if inorganic additives are used, such as dihydroxy aluminum sodium carbonate, or hydrotalcite. 3.2.7

Porous Parts

Porous parts are produced by the compaction and sintering method, vibratory compaction may be used (13). A cavity is filled with resin and vibrated to ensure uniform packing. The volume is then enclosed and heated to 175-205°C without applying pressure, and then cooled. Materials with extremely low bulk densities of 200-250 kg m~3 are obtained.

3.3

Properties

The specifications of UHMWPE are standardized in an ASTM publication (15). Properties of an UHMWPE are shown in Table 3.2. UHMWPE has a molecular weight that is 10 to 20 times greater than high density poly(ethylene). It has a molecular weight greater than 3MDalton. It is essentially insoluble in common solvents at room temperature. Its molecular weight must be determined by intrinsic viscosity in decahydronaphthalene at 135°C (13).

Ultra High Molecular Weight Poly(ethylene) 3.3.1 Mechanical

83

Properties

UHMWPE exhibits an outstanding sliding abrasion resistance, the highest notched impact resistance of any known plastic material and a low coefficient of friction (13). Further, these materials exhibit a high energy absorption and high sound-dampening properties. These properties are retained under cryogenic conditions. However, in general, adhesion of UHMWPE to substrates is poor, even when the surface is roughened. 3.3.2

Electrical Properties

UHMWPEs exhibit excellent dielectric and insulating properties. The base polymer is an effective electrical insulator with a dielectric constant of 2.3 at 2 MHz. The high surface resistivity may cause electrostatic discharges. It can be reduced by the addition of carbon black. 3.3.3

Optical

Properties

The natural color of plain UHMWPE is opaque white. Of course, it can be loaded with pigments. 3.3.4

Other Properties

The water absorption is negligible. Further, the materials show a good chemical resistance. The chemical resistance to most strong oxidizing agents, is excellent. Aromatic and halogenated hydrocarbons cause only slight surface swelling at moderate temperatures. Unfortunately, the flammability of UHMWPE is high. It ignites readily and burns after removal of the source of ignition, similar to ordinary PE. Fabricated parts can be machined with standard wood or metal fabricating machines (13).

3.4

Special Additives

UHMWPE can be formulated with additives and fillers. However,

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this is not very effective, since there are only weak interactions between the basic material and the filler. Because the resin is viscoelastic, any additive must be homogeneously mixed prior to processing. Hardness, creep resistance, dimensional stability, and the coefficient of thermal expansion, can be improved by reinforcing materials or fillers, i.e., (micro) glass spheres, glass fibers, graphite, aluminum powder, talc, chalk, silicates, and carbonates. Crosslinking can be achieved by the addition of organic peroxides, which improves the wear resistance. In addition, crosslinking occurs by the treatment with energy rich radiation. If the fabricated parts are continuously exposed to high temperature, the addition of antioxidants is advisable. The heat conductivity of UHMWPE is improved by the addition of metal powders such as copper, aluminum, and bronze. Also graphite is effective in this way. Satisfactory UV resistance is obtained by the admixture of UV stabilizers.

3.5

Applications

UHMWPE is used in • • • • 3.5.1

Medial applications, Highly stressed parts, Self lubricating bearings and bushings, and Cryogenic applications. Prosthetic Joints

When a human joint has been destroyed or damaged by disease or injury, surgical replacement, also addressed to as arthroplasty, is normally required. A total joint replacement includes components that simulate a natural human joint (16): • A spherically shaped ceramic or metal ball, often made of cobalt-chromium alloy, • Attached to a stem, which generally is implanted into the core of the adjacent long bone, and

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Figure 3.1: Design of a Prosthetic Hip Joint • A hemispherical socket, which takes the place of the acetabular cup and retains the spherical ball. This hemispherical socket typically is a metal cup affixed into the joint socket by mechanical attachments and lined with a suitable polymeric material so that the ball can rotate within the socket, and so that the stem, via the ball, can pivot and articulate. The basic design of a prosthetic hip joint is shown in Figure 3.1. A prosthetic hip joint includes a ball, which is connected by a neck to a body and a stem. The stem may be held in place in the femur by a variety of methods, including use of cementing agents, an interference press fit, a threaded mechanism, and biological fixation. The cupshaped socket is anchored in the pelvis by cementing, press fitting, use of screws, etc. Basic principles for the construction of prosthetic joints are figured out in great detail in the literature (17). UHMWPE is commonly used to make prosthetic joints such as artificial hip joints (12). 3.5.1.1

Common Issues

Three basic problems may cause a total joint replacement to fail or to have a limited service life. The first problem, arises, because the elastic modulus of the stem greatly exceeds that of the bone. Flexural loading caused by walking creates local cyclic stress concentrations due to the non-compliance of the stem. These stresses can be intense and even severe enough to cause death of local bone cells. If this

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occurs, pockets of non-support are created, and the stem may loosen or fail. The second basic problem is known as ball-cup friction and wear. It results from frictional wear between the hemispherical bearing and the polished spherical ceramic or metal ball attached to the stem. The third problem is addressed to as sub-surface fatigue. It results from the brittleness of the UHMWPE bearing and the tendency of the UHMWPE bearing to fail under reciprocating applied loads. Some insight into the cause of failure due to ball-cup friction and wear has been gleaned from histological studies of the surrounding tissue. Histological studies show that the surrounding distressed tissue typically contains extremely small particles of UHMWPE which range from sub-micrometers to a few micrometers in size. Larger particles of UHMWPE appear to be tolerated by the body, as is the solid bulk of the UHMWPE bearing. However, the body apparently does not tolerate smaller particles of UHMWPE. In fact, these small particles of UHMWPE cause powerful histiocytic reactions by which the body unsuccessfully attempts to eliminate the foreign material. Agents released in this process attack the neighboring bone to cause wear debris-induced osteolysis which, in turn, leads to a loss of fixation and loosening of the prosthesis due to remodeling of the bone (16). From a medical view, tissue necrosis and interface osteolysis, in response to UHMWPE wear debris, are the primary contributors to the long-term loosening failure of prosthetic joints. For example, wear of acetabular cups of UHMWPE in artificial hip joints introduces many microscopic wear particles into the surrounding tissues. The wear debris stimulates macrophages to produce mediators of osteolysis, which causes aseptic loosening of the implant (18). The biological activity of PE wear debris is dependent upon the size and number of particles present (19). Particles of the size 0.24, 0.45, and 1.7 μ m are most biologically active. The specific biological activity SBA of the wear debris is calculated using the equation (18).

SBA = B(r)C(c)| o ;¡¡; + B{r)C{cf\^m + B(r)C(c)|11^™ ,

(3.2)

where B(r) is the biological activity function of a given particle size

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and C(c) is the volumetric concentration of the wear debris for a given particle size. In summary, the reaction to these particles includes inflammation and deterioration of the tissues, particularly the bone to which the prosthesis is anchored. Eventually, the prosthesis becomes painfully loose and must be replaced (12). 3.5.2.2

Composites

Implantable prosthetic bearings may be constructed from a composite material having a first layer and a second layer (20). The first layer has an articulating surface defined therein, whereas the second layer has an engaging surface defined therein for engaging either another prosthetic component or the bone itself. The first layer is constructed of a UHMWPE, whereas the second layer is constructed of a copolymer of ethylene and an acrylate. The use of such an ethylene/acrylate copolymer provides a number of advantages. The ethylene portion of the copolymer is particularly well suited for adhering to the PE of the first polymer layer during fusion of the first polymer layer and the second polymer layer to one another. Further, the acrylate portion of the copolymer is particularly well suited for adhesion to bone cement, such as bone cement that includes poly(methyl methacrylate). Thus, using such a copolymer in the construction provides for ease of implantation in regard to a bearing designed for cement fixation. In particular, the ethylene portion of the copolymer is compatible with and provides for adhesion to the PE of the first layer, whereas the acrylate portion of the copolymer is compatible with and provides for adhesion to commonly utilized bone cements. 3.5.1.3

Improving Wear Resistance

Improving the wear resistance of the UHMWPE socket and, thereby, reducing the rate of production of wear debris would extend the useful life of artificial joints and permit them to be used successfully in younger patients. Consequently, numerous modifications in physical properties of UHMWPE have been proposed to improve its wear resistance. In particular, modifications of UHMWPE include (12):

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Engineering Thermoplastics: Polyolefins and Styrenics 1. 2. 3. 4.

Annealing, Protective Coating (16), Reinforcement with carbon fibers, Post-processing treatments such as solid phase compression molding, 5. Radiation sterilization (21), and 6. Crosslinking (21,22). Annealing. In order to improve the wear resistance, acetabular cups have been fabricated from conventionally extruded bar stock that previously had been subjected to heating and hydrostatic pressure. This procedure causes reduced fusion defects and increases the crystallinity, density, stiffness, hardness, and yield strength. Further, it results in an increased resistance to creep, oxidation and fatigue. Carbon Fibers. Indeed, carbon fiber reinforced PE and a heat pressed PE have shown relatively poor wear resistance when used as the tibial components of total knee prosthesis (23). Radiation Sterilization. In addition, the method of radiation sterilization to improve the wear resistance of UHMWPE components has been modified (24). This has typically involved packaging the PE cups either in an inert gas (25), in a partial vacuum or with an oxygen scavenger (12). Diamond Coatings. The friction between the metal and UHMWPE components can be reduced by coating one or both of the components with diamond-like carbon (DLC), which is chemically inert, biocompatible, and is known to have a low coefficient of friction. Unfortunately, the very properties of DLC that make it a desirable coating for parts that will be frictionally engaged make it difficult to achieve strong adhesion of the DLC coating to the substrate, particularly where deposition temperatures must be low. This limited adhesion problem can be exacerbated by a very high compressive stress, such as that found in a plasma-deposited DLC which is up to 8 G Pa. Therefore, is was concluded by some scientists that DLC, or at least plasma-deposited DLC, cannot be used in orthopaedic

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applications (26). However, a method has been developed for creating strong adhesion of the DLC coating to the spherical ball. This method consists in a solvent immersion step of the UHMWPE, followed by a ion beam assisted deposition of silicon. Eventually the deposition of DLC is done. Silicon is chosen because the DLC is known to adhere better to silicon that any other substrate, which is attributed to strong SiC bonds formed at the interface (16). Sintering is the preferred method of creating a diamond table with a strong and durable bond to a substrate material. A table of polycrystalline diamond may be manufactured and later attached to a prosthetic joint in a location such that it will form a bearing surface. The attachment could be performed by welding, brazing, or by the use of fasteners such as screws, bolts, or rivets (17). Although high pressure high temperature sintering is the preferred method for creating a diamond bearing surface, other methods for producing a volume of diamond may be employed as well. For example, either chemical vapor deposition (CVD), or physical vapor deposition (PVD) processes may be used. CVD produces a diamond layer by thermally cracking an organic molecule and depositing carbon radicals on a substrate. PVD produces a diamond layer by electrically causing carbon radicals to be ejected from a source material and to deposit on a substrate where they build a diamond crystal structure. The CVD and PVD processes have some advantages over sintering. Sintering is performed in large, expensive presses at high pressure of 45-68 kbar and at high temperatures, in the range 1200-1500°C Often the basic material does not allow these conditions. In contrast, CVD and PVD take place at atmospheric pressure or lower, so there no need for a pressure medium and there is no deformation of the substrates. Moreover, in sintering it is difficult to achieve some geometries in a sintered polycrystalline diamond compact. When CVD or PVD are used, however, the gas phase used for carbon radical deposition can completely conform to the shape of the object being coated, making it easy to achieve a desired non-planar shape. The finished component will tend to have large residual stresses caused by differences in the coefficient of thermal expansion and the modulus between the diamond and the substrate. While residual stresses can be used to improve the strength of a part,

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Engineering Thermoplastics: Polyolefins and Styrenics

they can also be disadvantageous. Only a few substrates are suitable for sintering. Typically tungsten carbide is used. When CVD or PVD is used, residual stresses can be minimized because CVD and PVD processes do not involve a significant pressures during manufacturing. These processes allow to place synthetic diamond on many substrates, including titanium, most carbides, silicon, and molybdenum. This arises because the temperature and pressure of the CVD and PVD coating processes are low enough that differences in coefficient of thermal expansion and modulus between diamond and the substrate are not as critical as they are in a high temperature and high pressure sintering process. A basic CVD reactor includes four components, namely (17): 1. 2. 3. 4.

Gas inlets, Power sources for the generation of thermal energy, a Stage or platform for placing the substrate, and an Exit port for removing the exhaust gases.

CVD reactors are classified according to the power source used. The power source is chosen to create the desired species necessary to carry out a thin film deposition of diamond. Some CVD reactor types include plasma-assisted microwave, hot filament, electron beam, single, double or multiple laser beam, arc jet and DC discharge. These reactors differ in the way, in which they transfer thermal energy to the gas species and in their efficiency in breaking the gases down to the species necessary for the deposition of the diamond. It is possible to have an array of lasers to perform local heating inside of a high pressure cell. Alternatively, an array of optical fibers could be used to deliver light into the cell. The basic process by which CVD reactors work is as follows: A substrate is placed into the reactor chamber. Reactants are introduced to the chamber via one or more gas inlets. For diamond CVD, methane CH4 and hydrogen H2 gases are preferably brought into the chamber in premixed form. Instead of methane, any carbon-bearing gas, in which the carbon has sp 3 bonding; may be used. Other gases may be added to the gas stream in order to control the quality of the diamond film, deposition temperature, gain structure and growth rate. These include oxygen, carbon dioxide, argon, halogens, and others.

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The gas pressure in the chamber is preferably maintained at about 100 torr. Flow rates for the gases through the chamber are preferably about 10 Ncm 3 min _ 1 for methane and about 100 Ncm 3 h - 1 for hydrogen. The composition of the gas phase in the chamber is preferably in the range of 90-99.5% hydrogen and 0.5-10% methane. When the gases are introduced into the chamber, they are heated. Heating may be accomplished by many methods. In a plasmaassisted process, the gases are heated by passing them through a plasma. Otherwise, the gases may be passed over a series of wires, such as those found in a hot filament reactor. Heating the methane and hydrogen will break them down into various free radicals. Through a complicated mixture of reactions, carbon is deposited on the substrate and joins with other carbon to form crystalline diamond by sp 3 bonding. The atomic hydrogen in the chamber reacts with and removes hydrogen atoms from methyl radicals attached to the substrate surface in order to create molecular hydrogen, leaving a clear solid surface for further deposition of free radicals. If the substrate surface promotes the formation of sp2 carbon bonds, or if the gas composition, flow rates, substrate temperature or other variables are incorrect, then graphite rather than diamond will grow on the substrate. There are many similarities between CVD reactors and processes and PVD reactors and processes. PVD reactors differ from CVD reactors in the way that they generate the deposition species and in the physical characteristics of the deposition species. In a PVD reactor, a plate of source material is used as a thermal source, rather than having a separate thermal source as in CVD reactors. A PVD reactor generates an electrical bias across a plate of source material in order to generate and eject carbon radicals from the source material. The reactor bombards the source material with high energy ions. When the high energy ions collide with the source material, they cause ejection of the desired carbon radicals from the source material. The carbon radicals are ejected radially from the source material into the chamber. The carbon radicals then deposit themselves onto whatever is in their path, including the stage, the reactor itself, and the substrate (17).

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Engineering Thermoplastics: Polyolefins and Styrenics

Crosslinking. Probably the most common technique to improve wear resistance is crosslinking. Several techniques of crosslinking have been described, including (18): • Radiation-induced crosslinking, and • Chemical crosslinking. Radiation-Induced Crosslinking. In the absence of oxygen, the predominant effect of ionizing radiation on UHMWPE is crosslinking (27). Crosslinking of UHMWPE forms covalent bonds between the polymer chains, which inhibit cold flow or creep of the individual polymer chains. Free radicals formed during irradiation, however, can exist indefinitely if termination by crosslinking or other forms of recombination do not occur. Furthermore, reacted intermediates are continuously formed and decayed. Exposure of these free radical species at any time, e.g., during irradiation, shelf-aging, or in vivo aging to molecular oxygen or any other reactive oxidizing agent can result in their oxidation. Extensive oxidation leads to a reduction in molecular weight, and subsequent changes in physical properties, including wear resistance (18). In order to reduce oxidation processes after y-sterilization, some orthopaedic manufacturers have implemented techniques to irradiate their materials under conditions that encourage crosslinking and reduce oxidation. These techniques include the use of inert gas atmospheres during all stages of processing, use of vacuum packaging, and post sterilization thermal treatments. These techinques are summarized in the literature (18). Chemical Crosslinking. In addition to irradiation crosslinking, chemical crosslinking of UHMWPE has been investigated as a method for the increasing wear resistance. Chemical crosslinking provides the benefit of crosslinking while avoiding the degradative effects of ionizing irradiation (18). However, residuals from chemical crosslinking, are a regulatory concern and may contribute to long-term oxidative degradation.

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Surface Crosslinking. The wear resistance of an UHMWPE implant, is improved by crosslinking its bearing surface layer, while leaving its non-bearing interior unaffected. Such a kind of crosslinking is achieved by electron beam irradiation or by chemical crosslinking. Typical electron energies are in the range of 0.6-0.9 MeV. The resulting article may be further treated to remove the residual free radicals that are generated by the crosslinking process. Further, a possibly oxidized top layer can be removed (28). When using electron beam crosslinking, the implant should be packaged in a low oxygen atmosphere during irradiation, in order to minimize oxidation and maximize crosslinking of the surface layer. In contrast, if an implant is electron beam irradiated in air, the outer layer of the bearing surface may then be removed, e.g., by machining, to eliminate the more oxidized and less crosslinked layer. In such a case, the depth of crosslinking penetration of the electron beam should be increased to take into account the thickness of the material to be eventually removed. The residual free radicals can be removed by (28): 1. 2. 3. 4.

Remelting, Annealing, Treatment with hydrogen, or Treatment with ethylene oxide.

In Figure 3.2 the increase of the melting temperature as a function of the distance from surface is shown. Silane Crosslinking. Further, silane crosslinked UHMWPE has been used for acetabular cups for total hip replacements in goats. In this case, the number of in vivo debris particles appeared to be greater for crosslinked materials than conventional UHMWPE (29). Microwave Supported Crosslinking. Because of abrasion in conventional UHMWPE, the body may react with inflammations and tissue alterations. The mechanical properties can be improved by additional crosslinking. Crosslinking is customarily achieved by way of intermediate stages involving radicals that are produced either by means of ionizing radiation or, by chemical processes.

94

Engineering Thermoplastics: Polyolefins and Styrenics 138

ü o

15MRad 10MRad 5 MRad

137

· o

CI)

3 05

i_

136

Φ

u. F Φ

h-

13S

O)

c

Cl>

134

¿¿ CO
133

Έ

132

1

1.5

2

2.5

Distance from Surface/[mml

3

3.5

Figure 3.2: Decrease of the Melting Temperature as a Function of the Distance from Surface (28)

An essential prerequisite for the application of the crosslinked material within an organism is that the radicals initially produced are completely eliminated by subsequent reactions. Otherwise, the radicals could bring about destruction of tissue, for instance by acting as carcinogens (30). However, the complete elimination of the radicals is problematic, because their stability and hence their lifespan is enhanced by various kinetic or thermodynamic effects. For instance, alkyl groups have a stabilizing action and there is also a steric intervention by substituents with a blocking action or reduced mobility owing to strong crosslinking. Thus, some radicals hardly have any opportunity for recombination and remain isolated in the matrix. Attempts have been made to eliminate the residual radicals by: • Tempering the workpiece at an elevated temperature (31), • External hydrogen exposure (32), • Electron beam crosslinking, which produces less free radicals (33), and • Special post crosslinking treatments (30).

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95

Highly crosslinked UHMWPE can be produced by irradiation of a blank UHMWPE with ionizing radiation, in particular by Xrays, y-rays or electron beams, in order to produce radicals. The subsequent treatment of the irradiated material consists in exciting free radicals, which have not recombined, by means of microwave radiation or ultrasound. The process is claimed to ensure a substantially complete recombination of the free radicals. In addition, the crosslinking of the UHMWPE is also further optimized (30). Microwave radiation exhibits advantages over conventional heating. The excitation is brought about in the immediate surroundings of a polar structural element, and it causes a heating of the polar components. Essentially no heating of the further surroundings of the polar structural element is done directly by the microwave radiation. Hence, the microwave radiation makes it possible to restrict heating within the matrix to the immediate vicinity of the radicals. The increased kinetic energy of the free radicals and their surroundings in turn results in an increased mobility of the electrons involved, and to a migration of the impaired electron, until another radical comes close together in order to allow e.g., recombination or disproportionation reactions. The frequencies of the microwave radiation applied are in general in the range between 20 MHz and 300 GHz, the frequencies in any particular case being adjusted in particular so as to induce carbon-carbon and carbon-hydrogen binding in the vicinity of the radicals. Ultrasound can be used to supplement or replace the microwave radiation. Ultrasound effects a high frequency mechanical vibration that warms the interior of the exposed object. In this case, the sample can exposed, and heated, as a whole. However, because ultrasonic waves can be so readily focused, it is also possible to apply them in bundled form so that they act on certain selected regions of the blank, for instance by sweeping along a raster. When ultrasound is used as energy carrier, a sound intensity in the range from 5-10 W cm" 2 is employed. This energy is sufficient to heat the material up to or even above its melting point. As a result, the diffusion velocity of the free radicals in turn increased. In addition, in the fluid phase of the matrix, sonochemical reactions are possible, based on cavitation. Such cavitation is associated with

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extremely high temperatures lasting for only a short time, which cause molecular dissociation and a subsequent recombination of the radicals thus produced, which enhances the migration ability of the original radical electron. Controlling the Crosslinking Density. The selective, controlled manipulation of polymers using radiation chemistry can be achieved by preferential irradiation shielding. By using a shield made of selected materials, of a certain shape, the overall properties of the irradiated polymer may be controlled and tailored. Thus, the crosslinking density can be locally controlled in a direction perpendicular to the direction of irradiation by (34): 1. Shielding a part of polymer preferentially with a shield of varying shape, cross-section or thickness, and 2. Irradiating the preferentially shielded polymer in order to provide a gradient of crosslink density. Exemplary materials of shields include ceramics, metals, and glass. Suitable ceramics are alumina and zirconia. Suitable metals include aluminum, lead, iron, and steel. In a medical device, such as a finger joint spacer, shoulder meniscus, knee meniscus, or tibial knee inserts, regions where the elastic modulus is desirably lower, can be achieved. The preform is shielded so that the electron beam penetration is limited to those regions that will selectively be treated to have lower elastic modulus. The preform is then irradiated. The shield is then removed and the preform is further irradiated with the desired method without any more shielding. This leads to much higher cumulative dose levels in initially irradiated regions, where the low elastic modulus is desired. The higher dose levels in these regions will then lead to lower elastic modulus compared with the rest of the preform. 3.5.2

Microporous

Membranes

In general, UHMWPE is difficult to process because the resin does not flow when melted. However, there are alternative techniques to process this material, i.e., sintering, compression molding, ram extrusion, or gel processing. Microporous membranes can be made

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Table 3.3: Additives for Gel Processing Processing oils

Lubricants

Paraffinic oils Naphthalenic oils Aromatic oils Dibutyl phthalate Bis(2-ethylene)phthalate Diisodecyl phthalate Dicyclohexyl phthalate Butyl benzyl phthalate Ditridecyl phthalate

Alcohol ethoxylates Alkyl and alkyllaryl ethers Alkyl sulfates Amide surfactants Alkylphenol ethoxylates Betaines, sultaines Aminopropionates Ethoxylated fatty amines Guerbet ester Hydrogenated tallow glycerol Glycol and poly(ethylene glycol) esters Phosphate and phosphonate esters Sorbitan esters

from UHMWPE by gel processing (35). Thereby, UHMWPE is mixed with a processing oil and a lubricant. Processing oils or plasticizers have little solvating effect on UHMWPE at lower temperatures, e.g., at 60°C, but have a significant solvating effect at elevated temperatures, such as 200°C. Lubricants are compounds that, when added to an UHMWPE mixture, improve the processability of the UHMWPE mixture. Improved processability refers to a reduction in fusion time (the time it takes the polymeric system to melt or dissolve into a flowable solution. Improved processability is also seen as a reduction in energy consumption by the motor and as a reduction in mixture temperature when comparing systems with and without the lubricants. The results arising from this phenomenon include, but are not limited to, decreasing energy consumption, decreased thermal and mechanical degradation of the polymer, increased polymer strength, decrease machine wear, and increased polymer throughputs. Examples for additives for gel processing are shown in Table 3.3. For gel processing, the components, UHMWPE, optionally filler, processing oil, and lubricant are mixed. The components are preferably mixed in a continuous fashion, e.g., in a twin-screw extruder or a Brabender extruder, or a screw extruder with a blown film die. After mixing, the mixture is shaped. Shaping will depend upon the

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particular article that is desired. If a film or sheet is desired, then the appropriate die may be added to the extruder. After shaping, the articles are most often subjected to a step to remove the processing oil or solvent from the gel. An extraction, washing, or leaching step is introduced in order to remove the processing oil and the lubricant (36). In formulations with filler, the extruded sheets are preferably subjected to an extraction step to remove processing oil. After extraction, these sheets may have about 10-20% of residual oil. It is impossible to remove all of the processing oil and lubricant from any of the mixtures, so at least a trace amount will remain in the final sheets. In formulations without fillers, the extruded sheets are preferably subjected to an extraction step. After extraction, these sheets may have only residual amounts of oil and lubricant. Eventually, the articles are formed into microporous sheets or films. Such microporous sheets and films may be used as labels, diffusion membranes, and separators in electrochemical devices, e.g., batteries, capacitors, and fuel cells. Special examples for formulations are presented in the literature (35). Recall that a battery is an electrochemical device having an anode, a cathode, an electrolyte, and a separator sandwiched between the anode and the cathode and impregnated with the electrolyte. Membranes with filler are used preferably in lead acid batteries. Membranes without filler are used preferably in lithium batteries. 3.5.2.1 Shutdown Separators In lithium ion rechargeable batteries, shutdown separators are used as part of the overall battery safety system. These devices prevent, or substantially reduce the likelihood of thermal runaway, which may arise from short circuiting caused by physical damage, internal defect, or overcharging. The shutdown separators, will shutdown by a sufficient pore closure to substantially stop ion or current flow within the cell (37). Conventional shutdown temperatures are around 130°C. However, a microporous polyolefin battery separator with a shutdown temperature of 95-110°C and a melt integrity of more than 165°C can be made from a basic UHMWPE formulation (38).

Ultra High Molecular Weight Poly(ethylene) 3.5.3

99

Binders for Filter Materials

In purification filters for purifying liquids or gases, sometimes a loose bed of grains of an adsorbent material, such as activated carbon, is located between two porous walls which confine the grains. Since there is no cohesion within the granular material, the flow and filter use period are difficult to control. In the flow of the filtrate and as a result of fracturing, relocation of various particle size fractions or washing out or local blockages caused by fines can occur. In particular, the adsorbency of the granular material resulting from internal porosity of the grains is effective only to a small extent. Since most of the filtrate flows past the filter material through the interstices between the grains and essentially contacts only the surface of the grains. Thus, activated carbon filters are treated with binder materials in order to reduce the drawbacks indicated above (39). Filter materials are produced by dry mixing very fine activated carbon with a UHMWPE type. The mixture is introduced into a mold and heated in the absence of air to a temperature, which is significantly above the melting range of the binder. At these temperatures, the binder melts slowly. The process steps of dry mixing, introduction into the mold, compaction, heating according to a time program and demolding can be readily carried out in mass production. 3.5.4

Fibers

Though the processing UHMWPE is known to be extremely difficult, the manufacture of fibers is highly suggestive, since products made from such fibers are very strong, tough and durable. Numerous techniques related to the fabrication of fibers made from UHMWPE have been described. Fibers can be fabricated from films by subsequent splitting (40,41). A process for the production of films and fibers of UHMWPE below 2 mil (=1/1000 inch) in thickness has been described (42). This process involves the calendering and drawing the tapes at a temperature above the melting point of the UHMWPE. Fibrillation, is done by a fibrillating roll, i.e., a rotating steel roll incorporating slitting teeth about its periphery. This process yields a fiber that is much more flexible, pliant and softer. Consequently,

100

Engineering Thermoplastics: Polyolefins and Styrenics Table 3.4: Examples of commercially available UHMWPEs Tradename Dyneema® Spectra Tivar Polystone-M Tensylon Gardur GUR (Series) Devlon UHMWPE UTEC (Series) Avalon 37 Lennite (Series) Lubriblend® PE 5902 Stamylan® (Series)

Producer Royal DSM Honeywell Quadrant EPP Röchling Engineering Plastics Integrated Textile Systems Garland Manufacturing Ticona Devol Engineering Polymers Braskem Greene, Tweed & Co. Westlake Plastics Company TP Composites, Inc. DSM Engineering Plastics

such a product can be more easily woven and is much more comfortable to the wearer of a garment, such as a ballistic vest produced from this material. In addition, the availability of such a soft material woven from the thinner and more flexible fibers of the UHMWPE material allows the production of, ballistic vests comprised of multiple layers of fabric thus providing enhanced ballistic protection to the wearer. Further, the thin films or fibers may be used in diverse other applications such as dental floss and sails for sailing boats.

3.6 Suppliers and Commercial Grades Examples of commercially available UHMWPEs and suppliers are shown in Table 3.4. Tradenames appearing in the references are shown in Table 3.5.

3.7

Safety

Virgin UHMWPE grades are in compliance with U.S. Food and Drug Administration regulations (13).

Ultra High Molecular

Tradename Description

Weight Poly(ethylene)

Table 3.5: Tradenames in References Supplier

Ageless® Grace & Co. Iron oxide (25) Albrite® Rhodia UK Ltd. Phosphorus containing chemicals (35) Alkamuls® EGDS Rhodia Inc. Corp. Glycol distearate (35) Alkamuls® EL-620 Rhodia HPCII Sorbitan monooleate (35) Alkamuls® GMS Rhodia Inc. Corp. Glycerol monostearate (35) Alkamuls® JK Rhodia Inc. Corp. Guerbet ester (35) Alkamuls® SML Rhodia Inc. Corp. Sorbitan monoester (35) Alkamuls® SMO Rhodia HPCII Sorbitan monooleate (35) Alkamuls® STO Rhodia HPCII Sorbitan trioleate (35) Amgard® TOF Rhodia Inc. Corp. Phosphate ester (Flame Retardant) (35) ARCOprime® 400 Atlantic Richfield Co. Mineral oil (36) Crossfire® I Iowmedica Osteonics Corp. Crosslinked Poly(ethylene) (12) Dura ph os® Rhodia Inc. Corp. Phosphate ester (35) Duration™ Howmedica Osteonics Corp. Stabilized UHMWPE (12) Exxsol® D30 Exxon Isoparaffinic hydrocarbon solvents (the number refers to approxiumate flashpoint in°C) (5) GUR® (Series) Ticona UHMWPE (39) Hi-Sil® SBG PPG Industries, Inc. Precipitated silica (36)

101

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Styrenics

Table 3.5 (cont): Tradenames in References Tradename Description

Supplier

Igepal® CO-210 Rhodia HPCII Nonylphenol ethoxylates (35) Igepal® CO-630 Rhodia HPCII Nonylphenol ethoxylates (35) Igepal® RC-630 Rhodia HPCII Dodecylphenol ethoxylates (35) Irganox® (Series) Ciba Geigy Hindered phenols, polymerization inhibitor (36) Isopar® G Exxon Isoparaffinic solvent (6) Kaydol® oil Witco Corp. Mineral oil (36) Kemester® 1000 G Crompton Corp. Glycerol trioleate (35) Lucentite™ Co-Op Chemical Co. Organophilic clay (10) Marlex® BHB 5003 Chevron Phillips Chemical Comp. Metallocene catalyzed ethylene copolymers (MCP) (8) Miranol® Rhodia Inc. Alkylaspartic acid, ampholytic detergent (35) Mirataine® CBS Rhodia Inc. Corp. Coco betaine sultaine (35) Mirataine® COB Rhodia Inc. Corp. Coco oleamidopropyl betaine (35) Mylar® (Series) DuPont Poly(ethylene terephtalate) (31) Neustrene® 059 Chemtura Corp. Hydrogenated tallow glycerol (30% palmitic, 60% stearic) (35) Neustrene® 064 Chemtura Corp. Hydrogenated tallow glycerol (88% stearic, 10% palmitic) (35) Petrac® CZ81 Synpro Corp. Lubricant (35,36) Polyblak® 1850 Color concentrate A. Schulman, Inc. (36) Rhodacal® N Rhodia Inc. Sodium napthalene sulfonate (35)

Ultra High Molecular

Weight Poly(ethylene)

Table 3.5 (cont): Tradenames in References Tradename Description

Supplier

Rhodafac® LO-11A Phosphate ester (35) Rhodameen® (Series) Ethoxylated tallow amine (35) Rhodapex® CD-I 28 Ammonium caprylether sulfate (35) Rhodapon® BOS Sodium 2-ethylhexyl sulfate (35) Rhodapon® UB Sodium lauryl sulfate (35) Rhodaquat® DAET-90 Quaternary Amine Complex ditallow Rhodasurf® LA-12 Linear alcohol ethoxylates (35) Rhodasurf® LA-3 Linear alcohol ethoxylates (35) Rhonotec® 201 Antioxidant (36) Shellflex® 371 Processing oil (36) Supragil™ WP Dispersant (35) Sylopol® 5910 Catalyst support (8) TiPure® R103 Titanium dioxide (36) Tufflo® 6056 Mineral oil (36)

Rhodia Inc. Rhodia Chimie Corp. Rhodia Chimie Corp. Rhodia Chimie Corp. Rhodia Inc. Rhodia Chimie Corp. sulfate (35) Rhodia HPCII Rhodia HPCII Hoffmann La Roche Shell Rhodia Chimie Corp. Grace & Co. DuPont Atlantic Richfield Co.

103

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References 1. R. Otto, Process for the production of high molecular weight ethylene polymers, US Patent 3254070, assigned to Ruhrchemie Ag, May 31, 1966. 2. D. Netzer, Process for the coproduction of benzene from refinery sources and ethylene by steam cracking, US Patent 6677496, January 13, 2004. 3. K.W. Willcox, Prevention of fouling in polymerization reactors, US Patent 4182 810, assigned to Phillips Petroleum Company (Bartlesville, OK), January 8,1980. 4. W. Payer and J. Ehlers, Method for the production of olefin polymers and selected catalysts, US Patent 7157 532, assigned to Ticona GmbH (DE), January 2, 2007. 5. J. Ehlers, S. Haftka, and L. Wang, Method for producing a polymer, US Patent 7141636, assigned to Ticona GmbH (DE), November 28, 2006. 6. P.J. Garrison, L.R. Wallace, D.L. Wise, J.H. Meas, Jr., L.V. Cribbs, J.A. Merrick-Mack, and PL. Nygard, High molecular weight, medium density polyethylene, US Patent 6 486 270, assigned to Equistar Chemicals, LP (Houston, TX), November 26,2002. 7. EH. Syed and W.D. Vernon, Status of low pressure PE process licensing, New Generation Polyolefins, 7(6):18-27, June-July 2002. 8. J.L. Martin, J.J. Bergmeister, E.T. Hsieh, M.P. McDaniel, E.A. Benham, and S.J. Secora, Olefin polymerization processes and products thereof, US Patent 7119043, assigned to Phillips Petroleum Company (Bartlesville, OK), October 10,2006. 9. J.-C. Liu, Preparation of ultra-high-molecular-weight polyethylene, US Patent 6 635 728, assigned to Equistar Chemicals, LP (Houston, TX), October 21, 2003. 10. J.-C. Liu, Olefin polymerization with pyridine moiety-containing single-site catalysts, US Patent 7 091 272, assigned to Equistar Chemicals, LP (Houston, TX), August 15, 2006. 11. C.C. Tso, M. Hildebrand, P.J. DesLauriers, and Y Yu, Ultra high molecular weight polyethylene fractions having narrow molecular weight distributions and methods of making and using the same, US Patent 7241 620, assigned to Chevron Phillips Chemical Company LP (The Woodlands, TX), July 10, 2007. 12. F.-W. Shen, H.A. McKellop, and R. Salovey, Crosslinking of polyethylene for low wear using radiation and thermal treatments, US Patent 6800670, assigned to Orthopaedic Hospital (Los Angeles, CA) and University of Southern California (Los Angeles, CA), October 5,2004. 13. H.L. Stein, "Ultra high molecular weight polyethylene (UHMWPE)," in M.M. Gauthier, ed., Engineered Materials Handbook, Vol. 2, Engi-

Ultra High Molecular

14.

15. 16.

17. 18. 19.

20.

21. 22. 23. 24. 25.

Weight Poly(ethylene)

105

neering Plastics, pp. 167-171. ASM International, Materials Park, OH, 2nd edition, 1998. [electronic:] http://www.uhmwpe.org/downloads/ publications/steinUHMWPE1999.pdf. K. Clark, J. Ehlers, and L. Wang, Method for making articles by cold compaction molding and the molded articles prepared thereby, US Patent 6846869, assigned to Ticona LLC (Summit, NJ), January 25, 2005. Standard specification for ultra-high-molecular-weight polyethylene molding and extrusion materials, ASTM Standard ASTM D 4020-05, ASTM International, West Conshohocken, PA, 2007. G. Dearnaley and J. Lankford, Jr., Ultra high molecular weight polyethylene components treated to resist shearing and frictional wear, US Patent 6171343, assigned to Southwest Research Institute (San Antonio, TX), January 9, 2001. B.J. Pope, J.K. Taylor, R.H. Dixon, M.A. Vail, and K.M. Jensen, Prosthetic knee joint having at least one diamond articulation surface, US Patent 7 077 867, assigned to Diamicron, Inc. (Orem, UT), July 18,2006. M.L. Scott and S.C. Jani, Cross-linked ultra-high molecular weight polyethylene for medical implant use, US Patent 6 726 727, assigned to Smith & Nephew, Inc. (Memphis, TN), April 27, 2004. J.B. Matthews, T.R. Green, M.H. Stone, B.M. Wroblewski, J. Fisher, and E. Ingham, Comparison of the response of primary human peripheral blood mononuclear phagocytes from different donors to challenge with model polyethylene particles of known size and dose, Biomaterials, 21(20):2033-2044, 2000. R. King, D.E. McNulty, and T.S. Smith, Composite prosthetic bearing constructed of polyethylene and an ethylene-acrylate copolymer and method for making the same, US Patent 7186364, assigned to DePuy Products, Inc. (Warsaw, IN), March 6, 2007. R.M. Streicher, Influence of ionizing irradiation in air and nitrogen for sterilization of surgical grade polyethylene for implants, Int. J. Radiât. Appl. Instrum. C Radiât. Phys. Chenu, 31(4-6):693-698,1988. D. Dijkstra, W. Hoogsteen, and A. Pennings, Cross-linking of ultrahigh molecular weight polyethylene in the melt by means of electron beam irradiation, Polymer, 30(5):866-873, May 1989. C M . Rimnac, P.D. Wilson Jr., M.D. Fuchs, and T.M. Wright, Acetabular cup wear in total hip arthroplasty, Orthopaedic Clinics of North America, 19(3):631-636,1988. R.M. Streicher, Sterilization and long-term aging of medical-grade uhmwpe, Radiât. Phys. Chem., 46:893-896, 1995. Proceedings of the 9th International Meeting on Radiation Processing, 1994, Pt. 1. D.-C Sun and CF. Stark, Non-oxidizing polymeric medical implant, US Patent 6818020, assigned to Howmedica Osteonics Corp. (Mah-

106

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Thermoplastics:

Polyolefins

and

Styrenics

wah, NJ), November 16,2004. 26. G. Dearnaley and J. Lankford, Jr., Treatments to reduce frictional wear between components made of ultra-high molecular weight polyethylene and metal alloys, US Patent 5593719, assigned to Southwest Research Institute (San Antonio, TX), January 14,1997. 27. R.M. Rose, E.V. Goldfarb, E. Ellis, and A.N. Crugnola, Radiation sterilization and the wear rate of polyethylene, /. Orthop. Res., 2(4):393400,1984. 28. H.A. McKellop and F.-W. Shen, Wear resistant surface-gradient crosslinked polyethylene, US Patent 6494917, assigned to Orthopaedic Hospital (Los Angeles, CA) University of Southern California (Los Angeles, CA), December 17, 2002. 29. B.D. Ferris, A quantitative study of the tissue reaction and its relationship to debris production from a joint implant, British journal of experimental pathology, 71(3):367-373,1990. 30. H. Schmotzer, Method for producing implant parts from highly crosslinked uhmwpe and implant parts for human medicine, US Patent 7364685, assigned to Plus Orthopedics AG (Rotkreuz, CH), April 29, 2008. 31. K.A. Saum, W.M. Sanford, W.G. Dimaio, Jr., and E.G. Howard, Jr., Process for medical implant of cross-linked ultrahigh molecular weight polyethylene having improved balance of wear properties and oxidation resistance, US Patent 6017975, January 25, 2000. 32. J.V. Hamilton, M.A. Manasas, and T.M. Flynn, Method for improving wear resistance of polymeric bioimplantable components, US Patent 5 577368, assigned to Johnson & Johnson Professional, Inc. (Raynham, MA), November 26,1996. 33. S.L. Krebs, D.L. Pletcher, R. Gsell, D.F. Swarts, G.S. Meadows, and G.K. Taylor, Method for crosslinking uhmwpe in an orthopaedic implant, US Patent 6365089, assigned to Zimmer, Inc. (Warsaw, IN), April 2, 2002. 34. O.K. Muratoglu, Selective, controlled manipulation of polymers, US Patent 7 381752, assigned to The General Hospital Corporation (Boston, MA), June 3, 2008. 35. J.G. Yaritz and J.K. Whear, Ultrahigh molecular weight polyethylene articles and method of manufacture, US Patent 7238744, assigned to Daramic, Inc. (Charlotte, NC), July 3,2007. 36. R.R. Ondeck, R.W Pekala, R.A. Schwarz, and R.C. Wang, Very thin microporous material, US Patent 5 948 557, assigned to PPG Industries, Inc. (Pittsburgh, PA), September 7,1999. 37. K.V. Nguyen and C.G. Wensley, Shutdown battery separator made with a blend of polymer and oligomer, US Patent 6749961, assigned to Celgard Inc. (Charlotte, NC), June 15, 2004.

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Weight Poly(ethylene)

107

38. G. Samii, A.M. Samii, and D.C. Veno, Shutdown separators with improved properties, US Patent 6949315, September 27,2005. 39. S. Haftka, J. Ehlers, C. Barth, and L. Wang, Activated carbon filter, US Patent 6 770 736, assigned to Ticona GmbH (DE), August 3, 2004. 40. S. Kobayashi, T. Mizoe, and Y. Iwanami, Process for continuous production of polyolefin material, US Patent 5 200129, assigned to Nippon Oil Co., Ltd. (Tokyo, JP), April 6,1993. 41. S. Kobayashi, T. Mizoe, Y Iwanami, O. Otsu, S. Yokoyama, K. Kurihara, and H. Yazawa, Split polyethylene stretched material and process for producing the same, US Patent 5 578 373, assigned to Nippon Oil Co., Ltd. (Tokyo, JP) Nippon Petrochemicals Co., Ltd. (Tokyo, JP) Polymer Processing Research Institute Ltd. (Tokyo, JP), November 26,1996. 42. G.C. Weedon, C.P. Weber, Jr., and K.C. Harding, Ultra high molecular weight polyethylene fibers, US Patent 6 951 685, assigned to Integrated Textile Systems, Inc. (Monroe, NC), October 4, 2005.

This Page Intentionally Left Blank

4 Poly(methyl)pentene The structure of a poly (4-methy 1-1-pen tene) (TPX) homopolymer is shown in Figure 4.1. Actually, TPX is a registered trademark from various companies, with a different meaning. Sometimes TPX is also abbreviated as PMP.

4.1

Monomers

4-Methyl-l-pentene belongs to the class of the hexenes. It can be produced by the catalytic dimerization of propylene (1,2). The dimerizarion of propene with a high selectivity to 4-methyl-l-pentene can be achieved in the presence of a catalyst, which is obtained by dispersing metallic sodium and metallic potassium on a molded article comprising an anhydrous inorganic potassium compound and elemental carbon (3). The basic monomer for TPX is 4-methyl-l-pentene. However, homopolymers are not usual, instead copolymers with α-olefins are in use. In Table 4.1, several comonomers are listed and depicted in Figure 4.2.

^^C/H

CH2—OH—C/H2*"'*w

CH2 H3O

CH2

*-''~'3 ■'3^-'

^-'''3

Figure 4.1: Poly(4-methyl-l-pentene) homopolymer 109

110

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Table 4.1: C o m o n o m e r s for TPX (4) Monomer 4-Methyl-l -pentene Comonomers 1-Decene 1-Dodecene 1-Tetradecene 1-Hexadecene 1-Octadecene 1-Eicosene Comonomers for Grafting Maleic acid Fumaric acid Itaconic acid Citraconic acid Crotonic acid endo-cis-Bicyclo[2,2,l ]hept-5-ene-2,3-dicarboxylic acid (NADIC acid) Acrylic acid Methacrylic acid

ΟΠ2—OH

L/H2

Οπ2 — \-/Π3

¿H 3 4-Methyl-1 -pentene

CH3

Acrylic acid

Metacrylic acid

1-Decene

CHj

Itaconic acid

Figure 4.2: Monomers

Poly(methyl)pentene

111

4.2 Polymerization and Fabrication TPX is polymerized commercially by a Ziegler-Natta polymerization. Mostly copolymers are on the market. Besides a Ziegler-Natta polymerization, also a living polymerization process has been reported. 4.2.1

Ziegler-Natta

Polymerization

The homopolymerization and copolymerization of 4-methyl-l-pentene is generally carried out in a batch polymerization process (5). Batch polymerization refers to a polymerization method in which a quantity of the monomers are polymerized in a reaction vessel and then the resulting polymer is recovered from that reaction vessel upon the desired level of polymerization of the monomers. It is desirable to carry out such processes under conditions, which result in a slurry of particles of the desired polymer or copolymer in the polymerization diluent rather than a solution of the polymer or copolymer. The formation of such a slurry aids in the separation and purification of the resulting polymer. Copolymers of 4-methyl-l-pentene with an a-olefin are obtained when 4-methyl-l-pentene is initially polymerized in the absence of the comonomer and then the comonomer is added to the reaction vessel to permit copolymer formation. Initially, pure 4-methyl-lpentene homopolymer is produced in order to reduce the solubility of the later formed copolymer so that eventually the copolymer does not contain more than about 5% weight percent of homopolymer. Examples of α-olefins include 1-pentene, 1-hexene, 1-octene, etc. A suitable catalyst is titanium trichloride with diethylaluminum chloride as co-catalyst. Hydrogen is a chain transfer agent. When catalysts suitable for the polymerization of propylene are applied to the polymerization of 4-methyl-l-pentene, they show a fairly high level of performance but do not prove to be entirely satisfactory with regard to the yield of the TPX per unit weight of the catalyst or the proportion of a stereoregular TPX in the resulting polymerization product (6). In order to improve the performance of the polymerization or copolymerization of 4-methyl-l-pentene, it is important to meet a combination of two parameters, i.e., the selection of a catalyst system

112

Engineering Thermoplastics: Polyolefins and Styrenics

composed of specific components and the pre-polymerization of 4-methyl-l-pentene. A polymer with improved stereoregularity and bulk density can be produced advantageously on an industrial scale using catalysts with improved catalytic activity. Such catalysts are prepared from MgCl2, T1CI4 and phthalic anhydride (6). Further, it turned out to introduce a step of pre-polymerization. In this step the catalyst described just above is used. For the main polymerization, triethylaluminum and trimethylmethoxysilane are added. Hydrogen is used as the chain transfer agent and methanol is added after an appropriate time to stop the polymerization. The stereoregularity index of the polymer can be expressed as the percentage of the insoluble portion in boiling «-heptane based on the total amount of the polymer. The polymerization activity is expressed as grams of the entire polymer per m mol of titanium. The polymerization activity and the stereoregularity index are shown in Table 4.2. 4.2.2 Metallocene Catalyzed

Polymerization

The class of monocyclopentadienylamido (CpA) titanium complexes has attracted the interest for the polymerization of a-olefins with bulky side groups. This arises since conventional Ziegler-Natta catalysts are less effective in starting the copolymerization of ethene with 4-methyl-l-pentene. Homogeneous catalysts of the zirconium cyclopentadienyl type (Cp2M) with methylaluminoxane exhibit a low catalytic activity. . It has been observed that for the copolymerization CpA catalysts exhibit a higher catalytic than the Cp2M complexes with an identical ligand substitution pattern (7). A catalyst of the CpA type with high activity is shown in Figure 4.3. In the copolymerization of ethene with 4-methyl-l-pentene, a penultimate effect has been observed (8). The 4-methyl-l-pentene unit in the penultimate position causes a remarkable decrease of the ethene reactivity. For this reason, isolated units of ethene are decreased in the copolymer. Actually, just the reverse would be expected from the concept of steric hindrance. However, the particular microstructure is produced by highly isospecific catalytic sites.

Poly(methyl)pentene

113

Table 4.2: Properties of Polymers (6) Prepolymerization Yes No Yes Yes Yes Yes Yes

Silicon compound added in *-•polymerization pre F A B B F E D

main F F B F B F C

Activity of Ti

Stereoregularity

mmol(gTi)" 1 24,000 11,000 4,300 6,700 5,000 17,100 25,600

% 98.2 96.5 91.7 93.6 90.9 97.9 98.1

(A) None (B) Diphenyldimethoxysilane (C) Triethylethoxysilane (D) Triethylmethoxysilane (E) Trimethylethoxysilane (F) Trimethylmethoxysilane

Figure 4.3: Catalyst of the CpA Type (7)

114

Engineering Thermoplastics: Polyolefins and Styrenics &

B(C 6 F 5 ) 4

Figure 4.4: Zirconium Complex Catalyst (9) 4.2.3

Living

Polymerization

Amorphous isotactic TPX was synthesized from 4-methyl-l-pentene in the presence of the zirconium complex as the catalyst of living polymerization. The catalyst is shown in Figure 4.4. A number of linear isotactic copolymers of 4-methyl-l-pentene with 1-hexene and functionalized olefins, such as 5-(trialkylsiloxy)1-pentene, could be prepared under similar conditions (9). In Figure 4.5 the melting point of a TPX copolymer with varying amounts of 1-hexene obtained by living polymerization are given. 4.2.4

Modification

A TPX polymer can be modified by heating the polymer together with a modification monomer up to a temperature of 125-250°C, in a solvent and in the presence of a polymerization initiator. Likewise, the TPX is kneaded with the modification monomer at a temperature of 235-250°C in an extruder in the presence of a polymerization initiator, however, without solvent (10). The polymerization initiator is an organic peroxide type. Particular examples of the organic peroxides are shown in Table 4.3. The polymerization initiator is used in an amount of usually about 0.01-1% of the polymer. Examples of the solvents include 1. Aliphatic hydrocarbons, such as hexane, heptane, octane,

115

Poly(methyl)pentene

240 -

1 i

220 200 -

O

o c "o Q.

V

"·.

·-.· »·-,_

180 -

O)

•

160 -

•

140 120 •

100 -

1

0

10

1

T

20

30

40

1

1

50

60

1-Hexene/[°C]

Figure 4.5: Dependence of the Melting point of a TPX Copolymer on its Content of 1-Hexene

Table 4.3: Organic Peroxides (10) Peroxides Alkyl peroxides

Di-ferf-butyl peroxide 2,5-Dimethyl-2,5-di-f£Tf-butylperoxy-hexyne-3 Diisopropyl peroxide

Aryl peroxides

Dicumyl peroxide

Acyl peroxides

Lauroyl peroxide

Aroyl peroxide

Dibenzoyl peroxide

Ketone peroxides

Methyl ethyl ketone peroxide Cyclohexanone peroxide

Hydroperoxides

ferf-Butyl peroxide Cumene hydroperoxide

136

Engineering Thermoplastics: Polyolefins and Styrenics 2. Alicyclic hydrocarbons, such as methylcyclopentane, cyclohexane, 3. Aromatic hydrocarbons, such as benzene, toluene, xylene, ethylbenzene, and 4. Halogenated hydrocarbons, such as chlorobenzene, bromobenzene, o-dichlorobenzene, carbon tetrachloride.

These solvents can be used singly or in combination of two or more kinds. The solvent is used in an amount of usually about 100-5,000 parts by weight based on 100 parts by weight of the polymer. 4.2.5 Flash Spinning Blades and White described a flash spinning process for producing plexifilamentary film-fibril strands from fiber-forming polymers. A solution of the polymer in a liquid, which is a non-solvent for the polymer at or below its normal boiling point, is extruded at a temperature above the normal boiling point of the liquid and at autogenous or higher pressure into a medium of lower temperature and substantially lower pressure. This flash spinning causes the liquid to vaporize and thereby cool the exúdate, which forms a plexifilamentary film-fibril strand of the polymer. Preferred polymers typically include crystalline polyolefins such as poly(ethylene) (PE) and polypropylene) (PP). According to Blades and White, a suitable liquid for flash spinning (11): • Has a boiling point that is at least 25°C below the melting point of the polymer, • Is substantially unreactive with the polymer at the extrusion temperature, • Should be a solvent for the polymer under the pressure and temperature (3447-10342 kPa and 165-225°C) • Should dissolve less than 1% of the polymer at or below its normal boiling point, and • Should form a solution that will undergo rapid phase separation upon extrusion to form a polymer phase that contains insufficient solvent to plasticize the polymer.

Poly(methyl)pentene

117

Commercial spun bonded or flash spun products have been made primarily from PE plexifilamentary film-fibril strands and have typically been produced using trichlorofluoromethane as a spin agent. However, trichlorofluoromethane is an atmospheric ozone depletion chemical, and therefore, alternatives have been under investigation. There have been many other agents used for flash spinning PE to either minimize or eliminate the potential for ozone depletion. Plexifilamentary film-fibril strands of fiber-forming TPX having a tenacity of 1 p d e n - 1 have been produced*. Also blends of TPX with PE and PP can be fabricated (12). It is known that TPX has a higher melting point than either PE or PP (235°C - versus 140°C and 165°C, respectively) and as such can provide a flash spun product usable at higher temperatures. Rather the copolymers with around 85% 4-methyl-l-pentene are in use than the pure homopolymer. In addition, it can be blended with either PE or PP or both. The flash spun TPX exhibits a very good fibrillation, but it does not have the strength of PE. However, the plexifilamentary fibers made from TPX have a strength of greater than 0.5 p d e n - 1 , which is sufficient for many purposes. At the most, a strength greater than 1 p den - 1 can be achieved. Trichlorodifluoroethane (HCFC-122) is a co-spin agent, which lowers the cloud-point pressure. The cloud-point pressure means the pressure at which a single phase liquid solution begins to phase separate. At temperatures above the critical point, there cannot be any liquid phase present and therefore a single phase, supercritical solution phase separates into a polymer-rich/spin fluid-rich, twophase gaseous dispersion. Microcellular foams can be obtained by flash spinning and are usually prepared at relatively high polymer concentrations in the spinning solution, i.e., at least 40% synthetic fiber-forming polyolefin. Relatively low spinning temperatures and pressures that are above the cloud-point pressure can be used. Microcellular foam fibers may be obtained rather than plexifilaments, even at spinning pressures slightly below the cloud-point pressure of the solution. *p is the unit of gram-force pond, den is the unit of Denier, one Denier is the weight of a fiber of 9 km length

118

Engineering Thermoplastics: Polyolefins and Styrenics

Spin agents used are the same as those noted above for plexifilamentary, film-fibril materials. Nucleating agents, such as fumed silica and kaolin, are usually added to the spin mix to facilitate spin agent flashing and to obtain uniform small size cells (12).

4.3

Properties

TPXs are excellent in the heat resistance, transparency and other properties. Accordingly, these polymers are widely used for the manufacture of vessels for physical and chemical experiments, tablewares for electronic oven treatments, percolators, syringes for medical treatments and paper coatings for food vessels. Although TPXs are excellent in the heat resistance and other properties, they are somewhat defective in the moldability because the melting point is high. Therefore, it is very difficult to prepare a molded article having a complicated configuration directly from a TPX according to the melt molding method (13). The combination of physical properties and characteristics are due to its distinctive molecular structure, which includes a bulky side chain. Properties of standard grades can be found in internet pages maintained from the manufacturer (14). 4.3.1 Mechanical

Properties

TPX is a hard solid material, which can be mechanically shaped into various optical components like lenses and windows. TPX has a density of only 0.835 g e m - 3 . 4.3.2

Thermal Properties

TPX exhibits heat resistance, resistance against microwaves. For these reasons it is suitable in food packaging applications. It has a high melting point of 240°C (15, p. 219). Due to the high melting point and good temperature stability, TPX is used for autoclavable medical equipment, components in microwave devices, and as cookware.

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119

4.3.3 Electrical Properties TPX is a good insulating material. It is used in electric and electronic applications. Because of its outstanding dielectrical properties, TPX is used in the field of high-frequency applications. At 12 GHz, the dielectric constant η is 2.1 and tañó = 8 x 10" 4 . 4.3.4 Optical

Properties

TPX is a crystalline resin, however, it is transparent like glass and has an excellent transmission rate for visible light. In the UV-range it shows a better transmission compared with glass or other transparent resins. Due these properties, TPX can be used for cells in spectroscopy. Homopolymers of 4-methyl-l-pentene have some properties, which are particularly desirable such as transparency (5). Specifically TPX is used in CO2 laser pumped molecular lasers as output windows. Namely, it is transparent in the whole T Hz range. 4.3.5 Other Properties TPX shows a good oil and grease resistance. Moreover it has a low moisture absorption. TPX has a very low surface tension around 24 mN m" 1 . For example, PE has a surface tension oi 31 mN m" 1 and PTFE has a surface tension of 18 m N m - 1 . Because of its low surface tension, articles from TPX must be pretreated with e.g., corona, flame, plasma, etc., for printing, painting or bonding (16). TPX shows an excellent peelability from a wide variety of materials. Therefore, TPX is used in applications in that separating properties are important. For this reason, it can be used as a release material in the process of curing thermosetting resins. In Table 4.4, the separating force expressed as surface tension of various materials against an epoxy resin are shown. TPX does not mix with other thermoplastic resins, e.g., as polyethylene terephthalate) (PET) or PP. It can be used to impart microporous properties in films made from PET and PP.

120

Engineering Thermoplastics: Polyolefins and Styrenics Table 4.4: Separating Force from Epoxy Resins (17) Material

Surface tension /[mNrrt-1 ]

Poly(4-methyl-l-pentene) Fluorocarbon Poly (butylène terephthalate) Poly(ethylene terephthalate)

4.4

0 10 170 60

Applications

Applications include • • • • • • • •

Sonar covers, Speaker cones, Ultrasonic transducer heads, Synthetic paper, Cosmetic and chemical tubes, Heat resistant nonwovens, Gas permeable packaging, and Lightweight structural parts.

TPX is also FDA compliant for use in food processing machinery. Thus, it is often used for food packaging. 4.4.2

Membranes

Several types of membranes have been described, for a wide variety of applications. 4.4.1.1 Gas Separation Membranes TPX has a high selectivity for hydrogen gas permeation. Data of selected polymers are shown in Table 4.5. A method for effectively separating and continuously purifying high purity pentafluoroethane (HFC-125) from the crude HFC-125 uses permeation membrane basically composed of TPX (18). Gas separation membranes may be prepared in a continuous manner by passing a porous support, which may be backed by a fabric through a solution of TPX dissolved in an organic solvent, such as hexane. The support member is passed through the solution

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121

Table 4.5: Hydrogen Permeability of Selected Polymers (19) Polymer Ethyl cellulose Poly(ether imide) Poly(phenyleneoxide) Poly(sulfone) Poly(methylpentene) Poly(imide) (Matrimid®) Poly(ethersulfone) Poly(styrene) Poly(vinylidene fluoride) (Kynar) Poly(methyl methacrylate)

T/[°C]

Permeability/[Barrer]

30 30 30 30 30 30 35 30 30 30

87 7.8 113 14 125 28.1 8.96 23.8 2.4 2.4

while one side thereof is in contact with a roller, thereby permitting only one side of the support member to be coated with the polymer. After continuously withdrawing the support member from the bath, the solvent is allowed to evaporate and the resulting membrane is recovered (20). 4.4.1.2 Electrolytic Membranes Separators in lithium ion batteries must separate positive electrodes and negative electrodes to prevent short circuits, and must allow passage of electrolytes or ions. Porous films and nonwoven fabrics of resins are known separators. The lithium ion battery separators are also required to exhibit stable properties at high temperatures such as in charging, and therefore high heat resistance is desired (21). PE sheets manufactured by a drawing process or phase separation method are in practical use as lithium ion battery separators. They are composed essentially of porous films of ultra high molecular weight poly(ethylene). Porous films of high melting point polyolefins, PET and poly(amide)s (PA)s have been proposed for enabling uses at high temperatures. However, manufacturing porous films from high melting point resins is difficult. In contrast, nonwoven fabric separators are suited for mass production and possess advantageous high porosity and lightweight, so that various nonwoven fabrics and separators using thereof having high heat resistance and small pore diameters have been studied.

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Engineering Thermoplastics: Polyolefins and Styrenics

Melt-blown non woven fabric TPX are used as separator materials. They are thin, but sufficient in mechanical strength and possess superior shape retention at elevated temperatures. However, melt-blown nonwoven fabrics with a microscopic variation of basis weight in different parts are a further drawback. The variation changes little even after the melt-blown nonwoven fabrics are pressed or embossed with metal rolls or press plates. Accordingly, the fabrics or pressed products, when used as separators, cause a microscopic nonuniform passage of electrolytes or ions in different parts of the membrane. More uniform pore diameters and diameter distribution will reduce the internal resistance. An important factor to achieve this is in the process of press forming. The press forming is preferably accompanied by heating. If the temperature and the pressure in the pressing are too high, the fibers are excessively fusion bonded with each other and the pores are shut down. In this case, the lithium ion battery separator obtained causes an extremely increased internal resistance and is often unusable. When the temperature and the pressure are too low, the pressing cannot produce sufficiently microscopic pores and the separator obtained has a low elongation resistance and a poor strength. Preferably, the lithium ion battery separators range in average fiber diameter from 1-3 μ, and in basis weight from 10-20 g m - 2 The average fiber diameter and basis weight are substantially the same before and after the pressing. The lithium ion battery separator desirably has a porosity of 40 to 50%, and a thickness of 20^45 μ. A lithium ion battery separator with this porosity value provides a low internal resistance and does not pass electrode substances to prevent short circuits. The thickness in the above range is suitable for the separator to be applied to small sized lithium ion batteries (21). 4.4.1.3

Filter Supports

Filter materials suitable for gas analysis, especially for non-gravimetric gas analysis can be made as laminates. One layer acts as filter material and the other as support (22). The filter material is a poly(carbonate) (PC) membrane with a maximum pore size of 2 μ. The support is made from TPX. The support is thermally bound to the PC membrane.

Poly(methyl)pentene

123

Table 4.6: Properties of Selected Compositions (23) MFRa g(lOmin)- 1

a b c

EBb %

450/550 30 550/650 40 400/450 35 380/400 30 250/350 30 Melt flow index Elongationi at break Oxygen permeability

OX PERC cm m~ 2 d~ 1 at~ 1 3

2500 1200 2000 3200 8400

Seal Strength kp(15mm) l Temperature of Heat Seal Bar 280°C 285°C 290°C 4.0 6.1 3.6 3.5 2.3

5.0 6.2 4.4 4.2 2.5

4.6 5.5 4.1 3.8 2.1

The filters are suitable for a variety of gas analyzing and sampling protocols, including the EPA and the NIOSH protocols (24). Further, the filters are suitable for non-gravimetric analysis and sampling protocols, especially for monitoring submicron particulate matter in gas. 4.4.2 Heat Sealable

Compositions

Films made from TPX exhibit an insufficient heat sealability. A widely adopted solution for improving such insufficient heat sealability is addition of a low density poly(ethylene) (LDPE) homopolymer or an ethylene propylene copolymer. However, the addition of these polymers only result in little improvement in their heat sealability. Instead, the addition results in poor dispersion and deteriorated impact resistance (23). It has been proposed to improve the heat sealability of TPX by the addition of a propylene-a-olefin copolymer. Satisfactory results have been achieved by melt mixing a TPX polymer with an 1-butene polymer and a propylene polymer (23). Properties of selected compositions are shown in Table 4.6. The compositions thus obtained have excellent mechanical properties including heat resistance, heat sealability, and impact resistance as well as satisfactory gas permeability. Therefore, the compositions are an appropriate material for producing various structural materials by injection molding.

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Engineering Thermoplastics: Polyolefins and Styrenics

The compositions may also be extruded into films and laminate papers. The films have excellent mechanical properties, including impact resistance and tensile strength as well as satisfactory releasability and gas permeability. The films are also heat sealable and the heat sealed film has sufficient strength. Therefore, such films are quite appropriate for the use as vegetable wrapping films, industrial films, and bags for storing platelets and cells. In addition to such films, the compositions can be used in the production of tablewares and structural materials by injection molding(23). 4.4.3 Laminates for Packaging Films TPX is used in mold-releasing films, printed circuit mold-releasing materials, various containers, etc., because of its heat resistance, chemical resistance, mold-releasing properties, transparency and other properties (4). In application areas, which require mechanical strength, gas barrier properties and high temperature mechanical strength, among other properties, composites are needed. Vegetables and fruits are packaged with packaging media to prevent rotting or deterioration or to keep freshness. For example, vegetables, such as lettuce, sweet pepper, broccoli, asparagus, spinach and mushroom, or fruits such as peach are packaged with packaging media made of PP, LDPE, and the like to keep freshness. However, it is particularly difficult to keep freshness of vegetables and fruits having high respiration rates, such as broccoli and asparagus, so that development of packaging media capable of keeping freshness for a long period of time has been desired (10). The use of packaging media having excellent gas permeability is desirable to keep freshness of vegetables and fruits having high respiration rates. In order to increase the gas permeability of the packaging media, a method of thinning the packaging media can be thought, but if the packaging media are thinned, it becomes difficult to maintain strength appropriate for packaging media. Further, there is a limit to the thickness of the packaging media because production of thin packaging media is accompanied by technical difficulty. A method of opening fine holes in the packaging media to in-

Poly(methyl)pentene

125

crease the gas permeability has been previously described. This method, however, is undesirable from the hygienic viewpoint because there is a possibility of bacteria entering through the holes. In contrast, vegetables and fruits having low respiration rates are desired to be packaged with packaging media having low gas permeability to keep freshness. Thus, as materials of the packaging media for keeping freshness of vegetables and fruits, those having gas permeability corresponding to the respiration rate should be employed. In general, it has been difficult to control the gas permeability of the packaging media over a wide range of high permeability to low permeability. However, a laminate consisting of a layer of TPX, an intermediate layer of an adhesive resin composition and a layer of an olefin polymer has excellent peel resistance and can be easily controlled in the gas permeability (10). One the attempt to give improved mechanical properties to TPX is to laminate the polymer and a resin containing polar groups, such as ethylene vinyl acetate and PA. These polymers exhibit excellent gas barrier properties, and the lamination of TPX makes an improvement in the gas barrier properties. Furthermore, PA, in particular biaxially-oriented PA, shows an excellent rigidity, toughness, impact resistance (4). Laminate samples are prepared by overlaying an ethylene vinyl alcohol polymer film, adhesive resin film and TPX film and are press-molded. 4.4.4

Overwrap Films

Overwrap films are used as wrappers of foods under storage or cooking. Conventional overwrap films are made of thin films of poly(vinyl chloride) or poly(vinylidene chloride), which are capable of withstanding heat at temperatures of about 140°C. Since the use of overwrap films has expanded, a demand has arisen for products that can withstand use at even higher temperatures, namely, those which have higher heat resistance. Polymers based on TPX melt at 220-240°C and are known to exhibit high heat resistance. Thus, overwrap films with high transparency and heat resistance

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Engineering Thermoplastics: Polyolefins and Styrenics

can be produced by shaping 4-methyl-l-pentene based polymers into films (25). However, films of 4-methyl-l-pentene based homopolymers are unsatisfactory, not only in flexibility, but also in tackiness, which is an important property in the case where they are to be used as wrappers. Instead, compositions comprising of TPX, a butene based liquid polymer and a 1-butene based solid polymer exhibit not only high heat resistance in the range of 190°C, but also good flexibility and tackiness and, hence, are advantageous to be used as heat resistant wrappers (25). 4.4.5 Image Forming Solution Among the image forming materials are positive image forming materials of which the portion exposed to light or other forms of radiation, such as electron beams, X-rays, y-rays, and a-rays undergoes a photochemical reaction or degradation reaction and thereby becomes soluble in a liquid developer. These positive image forming materials are suitable for the formation of fine patterns and for information recording. A number of positive image forming materials, such as quinone diazides, poly(methacrylic acid ester)s, and poly(l-butene sulfone) are well known, but all of them are low in sensitivity and have small y-values as calculated from their photosensitivity characteristic curves. Their low sensitivity requires large exposure doses of light or radiation or long exposure times and thus cause practical inconvenience. Moreover, their small y-values cause the incident light or radiation to be reflected or back-scattered from the substrate, making difficult the formation of fine images. Especially in the case of information recording, these positive image forming materials fail to achieve high resolution and thus lead to a reduction in information storage density. Subsequently, an improved method based on TPX materials is described (26). A starting polymer of TPX having an intrinsic viscosity of 9.38 dl g _ 1 and a melting point of 237°C as measured with a differential scanning calorimeter was degraded in the presence of dicumyl peroxide. The degraded polymer had an intrinsic viscosity of 1.17 dl g _ 1 and a melting point of 212-220°C.

Poly(methyl)pentene

127

Then, an image forming solution containing 2% by weight of the degraded polymer was prepared by adding an appropriate amount of the polymer to cyclohexene, heating and shaking the resulting mixture at 70°C to dissolve the polymer completely, and cooling the resulting solution to room temperature. The degraded polymer remained in solution at room temperature. Using a spinner, this solution was applied to a silicone wafer at room temperature to form thereon a photosensitive layer having a thickness of 0.5 μ, and the wafer was then prebaked at 200°C. Thereafter, using an electron beam lithographic apparatus, a latent image having a pattern width of 0.5 μ was formed with electron beams having an exposure dose of 3.5 ^C m~2 and a width of 0.5 μ. Then, the exposed photosensitive layer was developed by treating it with trichloroethylene at 18°C for 15 s. The positive image so formed had a pattern width of 0.5 μ and a y-value of 5. Thus, the degraded polymer was found to achieve an approximately equal resolution at a lower exposure dose, as compared with poly(methyl methacrylate) (PMMA) known as a conventional image forming material (26). 4.4.6

Xerographic Devices

Attempts to transfer and so print images have been made previously. In the past there has not been a successful attempt to provide a single universal material, which can be used both in xerographic photocopiers, laser printers and the like and also permit transfer of full-color images from one surface to another without the use of intermediate means, such as adhesive materials and without loss of definition or color tones or image quality. It has been normal practice to use paper, etc., for carrying images which are copied from a photocopier or dry-ink or toner printer, but these images have, been fixed on the paper or other material as permanent images. The term permanent means that the image cannot be removed from the carrier without damaging it. In addition, it is also known to transfer images onto self-supporting films for use as overhead projection slides. With state of the art copiers and laser printers, it is possible to produce mirror images in the copiers themselves and for those mir-

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Engineering Thermoplastics: Polyolefins and Styrenics

rored images to be printed. Having that facility, it is then desirable to carry that image directly from the copier or printer onto a medium that will permit transfer of the image directly from the medium onto a substrate that is intended to carry the image permanently, e.g. the surface of a packaging blank. Poly(ethylene naphthalate) films are known for a number of years for overhead projection foils or films. A transfer material has been developed for transferring monochrome and full-color images produced by a xerographic process or a dry toner printing onto a substrate. The process requires the use of a film from TPX as the transfer material. This material is used to transfer the xerographic or dry toner image onto the substrate with the application of heat and pressure (27). It has been discovered that the use of TPX not only allows the problem of distortion to be overcome, but also allows transfer of fullcolor images to be effected directly or indirectly from a photocopier or printer onto any desired suitable surface. The TPX material, which is associated with the toner in the transferred image assists in providing a very strong bond between the image and whatever substrate the image is finally transferred to. It has also been found, when the image has been examined, after transfer to the intermediate image carrier, the exposed surface of the image has enhanced scratch resistance. The use of TPX permits complete transfer of the toner from its initial carrier onto many other surfaces including of paper, card, cardboard, all of which may be uncoated or coated with many different types of finish, and of glass, ceramics, woods, metals, plastics, etc. TPX has sufficient thermal stability to be useful within the range of temperatures at which the material can be used for effecting image transfer. 4.4.7 Acoustic Devices 4.4.7.1 Speaker Panels A high molecular weight PP resin composition, has been prepared which has excellent acoustic properties and rigidity and high specific gravity suitable for use in acoustic instruments including speaker panels or boxes. The composition comprises 30-80% of PP as a main component.

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129

The PP is either a homopolymer or a crystalline copolymer of PP with ethene, 1-butene, 1-pentene, 1-hexene, 4-methyl-l-pentene, 1heptene, 1-octene or 1-decene as comonomers (28). Supplementary components include 10-60% of calcium carbonate with an average particle size of 1-20 μ and barium sulfate.

4.4.7.2

Noise Absorption

A video projector needs a strong light source. Using conventional light sources, the heat produced must be guided away from the projector. A good cooling efficiency of optical elements including the electro-optical device is needed. Therefore, the projector must be provided with an intake fan arranged in the vicinity of the optical elements including the electro-optical device and a duct. The duct is connected to the intake fan and arranged to face an exhaust port formed in the casing. Specifically, there can be a problem that when the size of the fan must be increased, the airflow rate and air velocity of cooled air are increased, and the cooled air hits against the duct, producing wind noise, so that the projector is liable to be noisy. It has been shown that paper sheets made from TPX placed in the ventilation duct offer a solution to avoid the noise. TPX is hardly melted by heat of the high temperature air flowing inside the duct, the shape retention of the duct can be sufficiently secured even at the high temperature. When arranged in an electronic apparatus, the duct can be simply configured matching the shape of a space in the electronic apparatus, thereby improving the degree of freedom in designing the duct (29).

4.4.8

Miscellaneous

4.4.8.1

Bottle Closure

Copolymers of PP and methylpentene have been shown to be used as materials for bottle closures. A procedure for the fabrication of bottle closures has been reported (30).

130 4.4.8.2

Engineering Thermoplastics: Polyolefins and Styrenics High Temperature Scintillator

Nuclear radiation has been used for borehole and well analysis, generally referred to as logging. Detecting and measuring the radiation permits an evaluation of the properties of a formation surrounding the borehole and therefore, is used for locating and extracting, for example, radioactive mineral deposits and petroleum. High energy neutron generators are particularly useful in well logging applications. In such applications one important factor is accurate knowledge of the neutron pulses that irradiate the surrounding formation. For example, it is desirable to accurately measure the neutron output, e.g., the number of neutrons emitted by the neutron detector. In a conventional logging apparatus, the scintillation material is comprised of a specially formulated organic polymer or plastic. Many conventional plastic scintillators do not exhibit acceptable mechanical and optical properties when used at relatively high temperature of 75-175°C encountered in a borehole. TPX is considered a high temperature host polymer, which provides scintillator properties. A modified TPX is manufactured under the brand name THERMOSCIN. The material is temperature resistant and has a relatively high hydrogen content as compared to a conventional scintillation material (20). The modified TPX offers low efficiency for generating scintillation pulses. One reason for the low light output is that the TPX host polymer does not have an extended system of π-electronic bonding. Alternative materials are polymers consisting of p-terf-butylstyrene and 4-vinylbiphenyl (31). 4.4.8.3

Radiation Resistant Formulations

In the development of solutions for reducing the radiation risks associated with manned space flight, radiation shielding materials have been developed to protect personnel and equipment from the damaging effects of radiation, including galactic cosmic radiation. PE is a favorable material because it exhibits many high performance properties (i.e., strength, thermal, and optical). However, the use of PE is limited to low temperature applications and to those ap-

Poly(methyl)pentene 250

Neat TPX 0.5% CNT

Λ

131 • Δ

200 Λ

CL

w O

if

150 100

\

/*

W O

A

*

50

-50

1

1

0

50

1 -

100

1

1

150

200

Temperature/[°C] Figure 4.6: Loss modulus of TPX (32)

-i^—, 250

plications wherein visibility through the polymer is not required, because PE is an opaque polymer (32). The incorporation of carbon nanotubes (CNT)s into polymer matrices has resulted in composites that exhibit increased thermal stability, modulus, strength, electrical and optical properties (33-35). Several investigations have concluded that carbon nanotubes can also act as a nucleating agents for polymer crystallization (36,37). Various processing techniques have been employed in order to uniformly disperse the nanotubes. This is important to increase the interaction at the polymer-nanotube interface. CNTs are used that are single wall CNTs. CNTs are 100 times stronger than steel, exhibit both excellent electrical and mechanical strength, and are light in weight. Due to their weight, CNTs are thought to be ideal fillers in a TPX matrix in order to produce a composite with radiation resistant properties, as well as with enhanced electrical and mechanical properties. Materials that are light in weight are better in resisting galactic radiation and limiting secondary radiation (32). The change in mechanical properties is shown in Figure 4.6. The

132

Engineering Thermoplastics: Polyolefins and Styrenics

Table 4.7: Examples for Commercially Available TPX Polymers Tradename

Producer

Remarks

Crystalor

Chevron Phillips Chemical Company Mitsui Chemicals America, Inc. Honeywell

Off market ?

Westlake Plastics Company RTP Company

PMP PMP

TPX® (Series) Honeywell PMP (Series) Westlake PMP (Series) RTP Compounds (Series)

PMP Copolymer PMP

crystalline region as noted in the loss modulus data was found to enhance with the addition of carbon nanotubes, indicating good interaction between the polymer-nanotube interface.

4.5 Suppliers and Commercial Grades Suppliers and Commercial Grades are show in Table 4.7 TPX® is available in pellet form. Since it does not absorb water or moisture, it is not necessary to dry the material before processing provided that it has been stored under normal conditions (16). Because of its high melting point TPX is normally processed at high temperatures in a range of 300°C. In order to minimize the decomposition of TPX, a nitrogen-feeding at the hopper during the molding process is recommended. Due to its crystallinity TPX shows bigger mold shrinkage than e.g. PC of PMMA. Blow molding is rather difficult and limited to the direct blow molding process, because of the rhéologie characteristics. For the same reason the injection blow molding process does not work. Tradenames appearing in the references are shown in Table 4.8.

Poly(methyl)pentene

Tradename Description Alathon®

133

Table 4.8: Tradenames in References Supplier Lyondell Petrochemical Co.

Poly(ethylene) (12) Eval® EP-F Kuraray Co. Ltd. Saponified ethylene/vinyl acetate copolymer (13) Nuclepore® Whatman Inc. Corp. Laminate membrane (22) Teflon® Dupont Tetra fluoro polymer (21) TPX® RT-18 Mitsui Chemicals 4-Methyl-l-pentene polymer (13)

References 1. H. Imai, M. Matsuno, and M. Kudoh, Process for preparing 4-methyl-l-pentene, US Patent 4388480, assigned to Nippon Oil Co., Ltd. (Tokyo, JP), June 14,1983. 2. M. Yankov, J. Ninov, and P. Petrov, Process for production of pure 4-methyl-l-pentene, Chemical Engineering & Technology, 17(5), 1994. 3. R.S. Smith, Alkene dimerization, US Patent 5 243119, assigned to Ethyl Corporation (Richmond, VA), September 7,1993. 4. K. Noritomi and T. Takata, 4-methyl-l-pentene polymer compositions, and the laminates and adhesives using the compositions, US Patent 6458890, assigned to Mitsui Chemicals, Inc. (Tokyo, JP), October 1, 2002. 5. P.M. Stricklen, D.M. Hasenberg, and P. Rooney, Process for the copolymerization of 4-methyl-l-pentene, US Patent 5182330, assigned to Phillips Petroleum Company (Bartlesville, OK), January 26,1993. 6. N. Kashiwa and K. Fukui, Process for production of 4-methyl-l-pentene polymer or copolymer, US Patent 4 659 792, assigned to Mitsui Petrochemical Industries, Ltd. (Tokyo, JP), April 21,1987. 7. G. Xu and D. Cheng, Homo- and copolymerization of 4-methyl-l-pentene and ethylene with group 4 ansa-cyclopentadienylamido complexes, Macromoleades, 34(7):2040-2047, February 2001. 8. S. Losio, P. Stagnaro, T. Motta, M.C. Sacchi, F. Piemontesi, and M. Galimberti, Penultimate-unit effect in ethene/4-methyl-l-pentene copolymerization for a sequential distribution of comonomers, Macromolecules, 41(4):1104-1111,2008.

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Polyolefins

and

Styrenics

9. D. Kisun'ko, D. Lemenovskii, and A. Aladyshev, Synthesis of isotactic copolymers of 4-methyl-l-pentene by living polymerization catalyzed by zirconium non-metallocene complexes, Polynt. Sei. Ser. A, 48(12): 1227-1231, 2006. 10. T. Tanizaki, T. Nakahara, and M. Kubo, Poly (4-methyl-l-pentene) resin laminates and uses thereof, US Patent 6 265 083, assigned to Mitsui Chemicals, Inc. (Tokyo, JP), July 24, 2001. 11. H. Blades and J.R. White, Fibrillaed strand, US Patent 3081519, assigned to E. I. du Pont de Nemours and Company (Wilmington, DE), March 19,1963. 12. R. Akki and H. Shin, Flash spinning polymethylpentene process and product, US Patent 6 352 773, assigned to E. I. du Pont de Nemours and Company (Wilmington, DE), March 5,2002. 13. T. Shiomi and K. Funakoshi, Method of bonding 4-methyl-l-pentene polymers, US Patent 4386991, assigned to Mitsui Petrochemical Industries, Ltd. (Tokyo, JP), June 7,1983. 14. Mitsui Chemicals, Properties of standard TPX™ grades, [electronic:] http://www.mitsuichemicals.com/tpx_phy.htm, 2009. 15. K. Sudheer and V. Indira, Post Harvest Technolog}/ of Horticultural Crops, Vol. 7 of Encyclopaedia of Horticulture and Allied Science, Anmol Publ., New Delhi, 2007. 16. Mitsui Chemicals, Polymethylpentene processing method, [electronic:] http://www.mitsuichemicals.com/tpx_proc.htm, 2008. 17. Mitsui Chemicals, TPX™ polymethylpentene (PMP) characteristics, [electronic:] http://www.mitsuichemicals.com/tpx_cha.htm, 2009. 18. Y. Suzuki and H. Ono, Method for production of pentafluoroethane, JP Patent 2 007055 934, assigned to Showa Denko Kk, March 08, 2007. 19. L. Shao, B.T. Low, T.-S. Chung, and A.R. Greenberg, Polymeric membranes for the hydrogen economy: Contemporary approaches and prospects for the future, /. Membr. Set., 327(1-2):18-31, February 2009. 20. J.J. Simonetti, High temperature plastic scintillators, US Patent 4 713198, assigned to Sangamo Weston, Inc. (Norcross, GA), December 15,1987. 21. Y. Sudou, H. Suzuki, S. Nagami, K. Ikuta, T. Yamamoto, S. Okijima, S. Suzuki, and H. Ueshima, Separator for battery and lithium ion battery using the same, US Patent 7183 020, assigned to Mitsui Chemicals, Inc. (Tokyo, JP) Denso Corporation (Aichi, JP), February 27,2007. 22. J.G. Adiletta, Filter for gas analysis, US Patent 6672135, assigned to Pall Corporation (East Hills, NY), January 6,2004. 23. K. Kan and A. Yamamoto, 4-methyl-l-pentene polymer composition, US Patent 5922812, assigned to Mitsui Chemicals, Inc. (Tokyo, JP), July 13,1999.

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135

24. P.C. Schlecht and P.F. O'Connor, NIOSH Manual of Analytical Methods, National Institute for Occupational Safety and Health, Washington, DC, 4th edition, 1994. 25. Y. Nagase, M. Kobayashi, T. Kato, and S. Imuta, Heat-resistant overwrap film from 4-methyl-l-pentene and isobutylene and 1-butene, US Patent 5 338 792, assigned to Mitsui Petrochemical Industries, Ltd. (Tokyo, JP) Chugoku Resin Co., Ltd. (Yamaguchi, JP), August 16,1994. 26. H. Yoshida, M. Miyamura, K. Funakoshi, and R. Nagano, Positive image-forming method using 4-methyl-l-pentene polymer, US Patent 4 623 610, assigned to Tokyo Shibaura Denki Kabushiki Kaisha (Kawasaki, JP) Mitsui Petrochemical Industries, Ltd. (Tokyo, JP), November 18,1986. 27. RJ. Mabbott, Transfer materials, US Patent 6 929 847, assigned to Xyron UK Limited (Bolton, GB), August 16, 2005. 28. Y.U. Kim, YH. Kim, and D.S. Song, High-molecular weight polypropylene resin composition having excellent rigidity for acoustic instruments, KR Patent 100429466, assigned to Samsung Total Petrochemicals, April 19,2004. 29. H. Meguro, H. Abe, and T. Hashizume, Duct and electronic apparatus having the duct, US Patent 6 843 277, assigned to Seiko Epson Corporation (Tokyo, JP), January 18, 2005. 30. Y Hatakeyama and S. Kozuka, Method for forming bottle closure, US Patent 4485065, assigned to Yoshida Industry Co., Ltd. (Tokyo, JP), November 27,1984. 31. J.J. Simonetti, W.P. Ziegler, E.F. Durner, Jr., and C.D.M. Busser, High temperature scintillator, US Patent 6 884 994, assigned to Schlumberger Technology Corporation (Ridgefield, CT), April 26, 2005. 32. J.P Harmon and L.M. Clayton, Polymer/carbon nanotube composites, methods of use and methods of synthesis thereof, US Patent 7399 794, assigned to University of South Florida (Tampa, FL), July 15,2008. 33. R. Haggenmueller, H.H. Gommans, A.C. Rinzler, J.E. Fischer, and K.I. Winey, Aligned single-wall carbon nanotubes in composites by melt processing methods, Chem. Phys. Lett., 330(3-4):219-225, November 2000. 34. Z. Ounaies, C. Park, K.E. Wise, E.J. Siochi, and J.S. Harrison, Electrical properties of single wall carbon nanotube reinforced polyimide composites, Compos. Sei Techno!., 63(11):1637-1646, August 2003. 35. K.I. Winey, R. Haggenmueller, F. Du, and W. Zhou, Polymer-nanotube composites, fibers, and processes, US Patent 7285 591, assigned to The Trustees of the University of Pennsylvania (Philadelphia, PA), October 23, 2007. 36. K.P. Ryan, S.M. Lipson, A. Drury, M. Cadek, M. Ruether, S.M. O'Flaherty, V. Barren, B. McCarthy, H.J. Byrne, W.J. Blau, and J.N. Cole-

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man, Carbon-nanotube nucleated crystallinity in a conjugated polymer based composite, Chem. Phys. Lett., 391(4-6):329-333, June 2004. 37. K. Ryan, M. Cadek, V. Nicolosi, S. Walker, M. Ruether, A. Fonseca, J. Nagy, W. Blau, and J. Coleman, Multiwalled carbon nanotube nucleated crystallization and reinforcement in poly (vinyl alcohol) composites, Synth. Met., 156(2-4):332-335, February 2006.

5 Ionomers Ionomers are obtained by the copolymerization of an unpolar monomer with a polar monomer. There are several monographs on ionomers (1^1). The term ionomer was originally introduced in 1964 by Dupont to indicate a thermoplastic polymer containing both covalent and ionic bonds (5-7). By definition, ionomers are statistical thermoplastic copolymers consisting of (8): 1. A mono-olefin, 2. A mono-olefinically unsaturated acid, and 3. Optionally additional comonomers for purposes of modifying the chemical and physical properties of these copolymers, whereby 4. The acid groups of these copolymers are partially or totally neutralized with inorganic cations.

5.1

Monomers

Ionic copolymers are composed from an α-olefin with an olefin content of 80 mol-% and an ethylenically unsaturated carboxylic acid (6). Suitable olefins include ethylene, propylene, 1-butene, 1-pentene, 1hexene, etc. The second essential component of the base copolymer are monomers, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, etc. Although maleic anhydride is not a carboxylic acid in that it has no hydrogen attached to the carboxyl groups, it can be considered an acid for the purposes to be incorporated in 137

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Engineering Thermoplastics: Polyolefins and Styrenics Table 5.1: Monomers for Ionomers (6) Monomer

Remarks

Ethene Propene 1-Butene 1-Hexene Acrylic acid Methacrylic acid Itaconic acid Fumaric acid Maleic acid Maleic anhydride

non-ionic non-ionic non-ionic non-ionic ionic ionic ionic ionic ionic hydrolyzable

CHo^ = CH2

Ethene

UH;?—OH

OH3

Propene

OH

Acrylic acid Maleic anhydride Figure 5.1: Monomers used for Ionomers the copolymer. Preferred monomers are those in which the carboxylic acid groups are randomly distributed over the copolymer molecules. Monomers used for ionomers are shown in Table 5.1 and in Figure 5.1. Besides olefins as raw materials, other vinyl compounds are also in use.

5.2 Polymerization and Fabrication Copolymers of ethylene and unsaturated acids can be made by (9): • Grafting the acid onto poly(ethylene) (PE), by batch or con-

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139

tinuous polymerization of mixtures of monomers of ethylene and the unsaturated acid, • By polymerization of mixtures of monomers of ethylene and the acid in a tubular reactor, and hydrolysis of copolymers of ethylene and alkyl acrylates, which converts the ester groups to carboxylic acid groups. • Block copolymers can be made, whereby the chain segments of poly(acrylic acid) and the chain segments of PE form long polymer chains. 5.2.1

Processing

Ionomers can be processed by conventional methods, such as injection molding, continuous molding and blow molding. However, at the stage of processing the functional group that effects the ionomeric properties must be still masked. In other words, the ionomer in its final form with the ionic moiety cannot be processed by thermoforming. After processing, the functional group is activated into its ionic form. A special processing is the formation of membranes. Here, the material can be cast from solution. 5.2.2

High Acid Types

A high acid type contains more than 16% acid monomer (10). High acid ionomer types have been widely described in the production of golf balls. They are used in multi-piece balls that exhibit an enhanced travel distance while maintaining the playability and durability characteristics necessary for repetitive play (11). High acid ionomers are neutralized to various extents by several different types of metal cations, such as by manganese, lithium, potassium, calcium and nickel cations. Several types can be blended. It has been found that these by additional cations neutralized high acid ionomer blends produce compositions exhibiting enhanced hardness and resilience due to synergies, which occur during processing (12). Consequently, these metal cation neutralized high acid ionomer resins can be blended to produce substantially higher coefficients of

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restitution than those produced by the low acid ionomer compositions. 5.2.2.1 Microporous Oriented Fibers Such fibers can be produced, for example, as a copolymer composed from 80% ethene and 20% acrylic acid is extruded through a spinnerette die into a 500 μ diameter strand at 125°C and then drawn to a 10 μ diameter filament. The filament contains an orientation resembling to a cold-drawn filament (9). After several intermediate steps, eventually microporous chopped fibers are obtained that are useful as intermediates for forming high melting aluminum salt derivative fibers. This is effected by contacting the fibers with an aqueous solution of 0.5% aluminum sulfate. 5.2.3

Mechanisms of Crosslinking

We summarize here the different available mechanisms of crosslinking. Namely, in ionic polymers a special mechanism of crosslinking will become important as discussed below. 5.2.3.1

Elastomer Crosslinking

Polymeric hydrocarbon elastomers, such as natural rubber, are crosslinked or vulcanized by the use of sulfur, which reacts with the carbon of the unsaturated bonds in polymer molecules to form a bridge between two molecules so that one polymer molecule is covalently bonded to a second polymer molecule (6). If sufficient crosslinks of this type occur in the polymeric hydrocarbon, all molecules are joined in a single giant molecule. The characteristic property of a crosslinked polymer is its intractibility above the softening point or melting point that is normally observed in the uncrosslinked base polymer. Thus, whereas the uncrosslinked polymer has a marked softening point or melting point above which the polymer is fluid and deformable, the crosslinked polymer retains its shape and will tend to return that shape when deformed at all temperatures at which the polymer is stable and can not be permanently deformed. The once crosslinked polymer can no longer be fabricated.

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141

By the process of vulcanization, rubber elasticity, impact resistance, flexibility, thermal stability and many other properties are either introduced or improved. In addition, the crosslinking of nonelastomeric polymers increases the toughness, abrasion resistance and, particularly, the maximum service temperatures of the material. 5.2.3.2

Peroxide Crosslinking

In addition to the vulcanization of diene hydrocarbon polymers using sulfur, other methods of crosslinking hydrocarbon polymers, which do not require a double bond and which do not use sulfur have been developed. Thus, saturated hydrocarbon polymers and, in particular, PE, are crosslinked by reactions resulting from the addition of a peroxide to the polymer at elevated temperatures (6). Peroxides decompose to form free radicals, which in turn attack the polymer chain to form crosslinking sites, which then react to form crosslinks. Irradiation of PE also results in a crosslinked product by substantially the same mechanism except that the free radicals are generated by decomposition of the polymer itself. By either method, however, a product is obtained which is intractable and can not be further fabricated by techniques normally used in the fabrication of PE, such as melt extrusion or injection molding. Therefore, the improvement obtained in the solid state properties of a hydrocarbon polymer by crosslinking have been highly appreciated. However, crosslinking causes a tolerable loss in fabricability. Crosslinking reduces the crystallinity of saturated hydrocarbon polymers, thereby decreasing the stiffness and rigidity of the product. With the exception of elastomeric hydrocarbon polymers, other crosslinked polymers besides of ionomers have found little commercial success as compared to the uncrosslinked hydrocarbon polymers. 5.2.3.3

Ionic Crosslinking

Most simply, ionic crosslinking is achieved by the action of multivalent metal ions. Ionic crosslinks are weaker than covalent crosslinks. The shear-stress necessary to break the ionic crosslinks and, thus,

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make the copolymer melt fabricable is steadily increased with an increasing number of crosslinks beyond that necessary to achieve an infinite network. The melt fabricability of the ionic copolymer is affected not only by the number of crosslinks, but to a much greater degree, is affected by the nature of the crosslink. The combination of certain types of acid copolymers with certain metal ions results in intractable materials, which do not lend themselves to melt fabrication. Base copolymers with dicarboxylic acid comonomers, even those in which one acid radical has been esterified, when neutralized with metal ions, which have two or more ionized valences, result in intractable ionic copolymers at the level of neutralization essential to obtain significant improvement in solid state properties. Similarly, base copolymers with mono-carboxylic acid comonomers result in intractable ionic copolymers when neutralized to the indicated degree with metal ions, which have four or more ionized valences. It is believed that the nature of the ionic bond in these instances is too strong to be suitable for the formation of ionic copolymers, which exhibit solid state properties of crosslinked resins and melt properties of uncrosslinked resins. Metal ions, which are suitable in forming ionic copolymers can be divided into two categories (6): 1. Uncomplexed metal ions and 2. Complexed metal ions. In the uncomplexed metal ions the valence of the ion corresponds to the valence of the metal. These metal ions are obtained from the commonly known and used metal salts. The complexed metal ions are those in which the metal is bonded to more than one type of salt group, at least one of which is ionized and at least one of which is not. Since the formation of the ionic copolymers requires only one ionized valence state, it becomes apparent that such complexed metal ions are equally well suited. The utility of complexed metal ions employed in the formation of ionic copolymers corresponds in their ionized valences to those of the uncomplexed metal ions. The monovalent metals are, excluded but higher valent metals may be included depending on how many metal valences are complexed and how many can be ionized.

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143

In general, the concentration of the metal ion should be at least such that the metal ion neutralizes at least 10% of the carboxylic acid groups in order to obtain a significant change in properties. The degree of neutralization for optimum properties will vary with the acid concentration and the molecular weight of the copolymer. However, it is generally desirable to neutralize at least 50% of the acid groups. The degree of neutralization may be measured by several techniques. Infrared analysis may be employed and the degree of neutralization calculated from the changes resulting in the absorption bands. Another method comprises the titration of a solution of the ionic copolymer with a strong base. In general, the added metal ion reacts stoichiometrically with the carboxylic acid in the polymer up to 90% neutralization. Small excess quantities of the crosslinking agent are necessary to carry the neutralization to completion. However, a large excess of the crosslinking agent do not add to the properties of the ionic copolymer, since once all carboxylic acid groups have been ionically crosslinked, no further crosslinks are formed. The crosslinking of the ionic copolymer is carried out by the addition of a metal compound to the base copolymer. The metal compound, which is employed must have at least one of its valences satisfied by a group which is substantially ionized in water. The necessary ionization is determined by the water solubility of the metal when bonded solely to the ionizable salt group (6).

5.3

Properties

The polar groups in ionomers are suppressing the tendency of crystallization. Moreover, a ionic crosslinking is effected. Thus, both secondary valency forces and ionic forces are active. The special types of bonds effect a special toughness of the materials. However, ionomers are true thermoplastic materials. 5.3.1

Mechanical

Properties

The mechanical properties at elevated temperatures can be still improved by forming composites that contain the ionomer resin that

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is ionically crosslinked with a poly(amide) (PA) oligomer (13). Additionally, a PA resin is added to the composition. The mechanical strength at high temperatures is obviously improved by the polymer alloy effect, as compared with the mechanical strength attained by the single use of the component of the PA resin or the oligomer. 5.3.2

Thermal Properties

The melting point of ionomers is high, i.e., in the range of 300°C, which is close to degradation. 5.3.3

Electrical Properties

In contrast to most other thermoplastic materials, ionomers may serve as electrolytes.

5.4

Special Additives

5.4.1 Antistatic

Agents

Polymer films in the course of their handling can develop high charges of static electricity, which can have harmful consequences ranging from sparking, possibly causing fires, to adhering to oppositely charged surfaces to interfere with use of the film in packaging operations. For example, film used to package food may be more advantageously handled in the packaging operation if the food is not attracted to the film. Film attraction for the food can prevent the desired wrinkle-free packaging of the food by the film and can lead to leaking in the final packaging seal. Poly(oxyethylene) sorbitan monolaureate is a surface active compound which is also known as an internal or external antistatic agent for a great number of plastics. It has been found that this compound provides an almost instantaneous antistatic action (14). Usually antistatic agents develop their full activity only after a couple of days. The almost instantaneous antistatic action is extremely important during the production of films where operators are exposed with static built up on the extrusion equipment. Thus, the additive is useful in applications where dissipative properties are important, such as supported or unsupported sheets forming

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145

floor tiles and auto interior components, where use of the additive leads to the advantage that dirt and dust attraction, which is very annoying in these applications, is largely reduced. The antistatic agent is uniformly incorporated into the copolymer by conventional melt blending techniques. For example, the antistatic agent is blended with molten copolymer in a manner to form a homogeneous blend, using for example an extruder.

5.5

Applications

Ionomers are used in a wide field of applications, such as (15): • • • • • •

Electrolytic membranes, Automotive parts, Sporting Goods, Packaging, Membranes for wetting, and Solid bead catalysts.

Here we present a few recent developments in the field. 5.5.1 Fuel Cell Anodes The anode layer of polymer electrolyte membrane fuel cells typically includes a catalyst and a binder, often a dispersion of poly(tetrafluoroethylene) or other hydrophobic polymers, and may also include a filler, e.g., acetylene black carbon. Anode layers may also contain a mixture of a catalyst, ionomer and binder. The presence of a ionomer in the catalyst layer effectively increases the electrochemically active surface area of the catalyst, which requires a ionically conductive pathway to the cathode catalyst to generate electric current (16). 5.5.2

Solar Control

Laminates

Glass laminated products, i.e., safety glass are well known. Safety glass is characterized by high impact and penetration resistance, and by minimal scattering of glass shards and debris upon shattering. The laminates typically consist of a sandwich of a polymeric film or sheet interlayer that is placed between two glass sheets or panels.

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Beyond the well known safety glass commonly used in automotive windshields, glass laminates are incorporated as windows into trains, airplanes, ships, and nearly every other mode of transportation. In addition to safety, a desirable goal is the reduction of energy input into automobiles or buildings through the development of solar control glazing. Because the near infrared spectrum is not sensed by the human eye, a typical approach has been to develop glass laminates that prevent a portion of solar energy from the near infrared spectrum from entering the structure. Solar control compositions are composed of an infrared absorbing phthalocyanine, naphthalocyanine, and an ionomer (17). 5.5.3 Heat Seal Modifiers Low density poly(ethylene) (LDPE) may have unsatisfactory heat seal properties, as they often do not provide sufficient adhesion between the sealing layers to result in a good adhesive seal for a package. Efforts to improve the heat seal characteristics of LDPE by blending them with other materials, such as ethylene copolymers with methacrylic acid or acrylic acid, have not had universal success. Special PE formulations, including ionomers and poly(terpene) tackifiers have been presented (18). The individual components are melt blended in an extruder.

5.6

Suppliers and Commercial Grades

Examples for commercially available ionomers and suppliers are shown in Table 5.3. Tradenames appearing in the references are shown in Table 5.2.

Ionomers

Table 5.2: Tradenames in References Tradename Description

Supplier

Amilan® CM1017C Toray Industries Nylon 6 (13) Atmer® Uniquema Antistatic agent (14) Baydur® Bayer AG Poly(urethane) (12) Bayflex® (Series) Bayer AG Poly(urethane) (12) Crillet® I Croda France S.A. poly(oxyethylene) sorbitan monolaureate (14) Elastolit® SR Elastigran Polyetherpolyol (12) Escor® (Series) Exxon Mobil Ethylene acrylic acid copolymers (10-12) Estañe® B.F. Goodrich Co. Poly(ester urethane) (12) Hytrel® DuPont Poly(ester) elastomer (12) Iotek® Exxon Mobil Ionomer (12) Kraton® Shell Styrenic block copolymer (12) Pebax® Arkema Poly(amide imide) (antistatic agent) (12,13) Primacor® (Series) Dow Ethylene acrylic acid copolymers (12) Prism® Bayer AG Poly(urethane) RIM resins (12) Spectrim® (Series) Dow Poly(urethane) RIM resins (12) Surlyn® DuPont Ionomer resin (8,10-12,14) Texin® (Series) Bayer AG Thermoplastic poly(urethane) (12)

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Table 5.3: Examples for Commercially Available Ionomers (15) Tradename

Producer

Remarks

Amplify™ IO 3801B Bexloy® (Series)

Dow Plastics DuPont Packaging & Industrial Polymers Flex-O-Glass, Inc. A. Schulman Inc. A. Schulman Inc. A. Schulman Inc. ExxonMobil Chemical DuPont Packaging & Industrial Polymers Westlake Plastics Company

Food Applcations Automotive

Sur-Flex® SF-52 Formion® FI 1005-31 Formion® FI 131E Formion® FI 200HFU Iotek™ Ionomers 7010 Surlyn® (Series) Westlake Ionomer

Laminating film Automotive Adhesive Nylon Alloy Zinc ionomer Packaging & al. Prosthetics & al.

References 1. M.R. Tant, K.A. Mauritz, and G.L. Wilkes, Ionomers: Synthesis, structure, properties and applications, Blackie Academic & Professional, London, 1997. 2. W. Grot, Fluorinated ionomers, PDL handbook series, William Andrew Pub., Norwich, N.Y., 2008. 3. C.K. Shin, Block copolymer ionomers for ion conducting membranes, Verl. Dr. Hut, 2002, Originally published as PhD Thesis. 4. M. Pineri and A. Eisenberg, eds., Structure and Properties of Ionomers, Vol. 198 of NATO Science Series C, Springer, Berlin, 1987. 5. R.W. Rees, Copolymers containing metallic ions, CA Patent 690326, assigned to Du Pont, July 07,1964. 6. R. W. Rees, Ionic hydrocarbon polymers, US Patent 3 264 272, assigned to Du Pont, August 02,1966. 7. C.S. Tumosa, D. Erhardt, M.F. Mecklenburg, X. Su, PB. Vandiver, J.L. Mass, and A. Murray, Linseed oil paint as ionomer: Synthesis and characterization, in Materials Research Society Symposium Proceedings, Vol. 852 of Materials issues in art and archaeology VII: Symposium held November 30 - December 3, 2004, Boston, Massachusetts, USA, p. 25, Warrendale, PA, 2005. Materials Research Society. 8. L. Moll, Use of ionomers for sealing insulating materials, US Patent 7442659, assigned to Biologische Insel Lothar Moll GmbH & Co. KG (Schwetzingen, DE), October 28, 2008. 9. W.L. Vaughn and T.J. McKeand, Jr, Ionomers of ethylene/carboxylic acid copolymers, US Patent 5 320 905, assigned to The Dow Chemical

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Company (Midland, MI), June 14,1994. 10. M.J. Sullivan, Golf ball covers containing high acid ionomers, US Patent 6494 792, assigned to Spalding Sports Worldwide, Inc. (Chicopee, MA), December 17, 2002. 11. M.J. Sullivan, High acid ionomers and golf ball cover compositions comprising same, US Patent 6277921, assigned to Spalding Sports Worldwide, Inc. (Chicopee, MA), August 21, 2001. 12. T.J. Kennedy, III, D.M. Melanson, M.J. Tzivanis, and V. Keller, Golf ball with deep depressions, US Patent 7497791, assigned to Callaway Golf Company (Carlsbad, CA), March 3, 2009. 13. Y Yamamoto and E. Hirasawa, lonomer composition, US Patent 5210138, assigned to Dupont-Mitsui Polychemicals Co., Ltd. (Tokyo, JP), May 11,1993. 14. K. Hausmann, B. Rioux, and J.-M. Francois, Antistatic ionomer blend, US Patent 6630528, assigned to E. I. du Pont de Nemours and Company (Wilmington, DE), October 7, 2003. 15. IDES Integrated Design Engineering Systems, Ionomer applications, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/generics/Ionomer/Ionomer_ applications.htm, 2009. 16. S. Ye, Fuel cell anode structure for voltage reversal tolerance, US Patent 7608358, assigned to BDF IP Holdings Ltd. (Vancouber, BC, CA), October 27, 2009. 17. R.A. Fugiel, R.A. Hayes, W. Mahler, T.R. Phillips, and L.A. Silverman, Solar control laminates, US Patent 7622192, assigned to E.I. du Pont de Nemours and Company (Wilmington, DE), November 24, 2009. 18. G.M. Lenges and T.A. Libert, Heat seal modifiers for linear polyethylenes, US Patent 7635736, assigned to E. I. du Pont de Nemours and Company (Wilmington, DE), December 22, 2009.

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6

Poly(isobutylene) Poly(isobutylene) (PIB) is the earliest polyolefin that has been produced on a technical scale. A German patent was filed in 1931 (1), which was eventually published in 1937. Other patents followed (2). In 1938 PIB was marketed as Oppanol® B by BASF. Oppau is a district of Ludwigshafen (3). However, PIB is mostly manufactured as a block copolymer. Unsaturations in the backbone are common. Thermoplastic elastomers are composed of glassy outer blocks and rubbery inner blocks. Because of the phase separation of the glassy blocks into discrete domains, these materials behave like crosslinked rubbers at low temperatures. However, at elevated temperatures they can be processed in the same way as thermoplastics (4).

6.1

Monomers

Important momnomers for PIB polymers and copolymers are shown in Table 6.1 and in Figure 6.1. The introduction of halogenated monomers into the backbone results in highly increased vulcanization properties. Table 6.1: Monomers for Poly(isobutylene) Types Monomer

Remarks

Isobutene Isoprene Divinylbenzene 4-Methylstyrene

Basic monomer Comonomer for crosslinking Comonomer for branching and halogenation Comonomer for halogenation 151

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Engineering Thermoplastics: Polyolefins and Styrenics

Isobutene

Isoprene

4-Methylstyrene

1,4-Divinylbenzene

Figure 6.1: Monomers used for Poly(isobutylene) Using 4-methylstyrene as comonomer results in a saturated backbone that cannot be vulcanized as such. However, the pendant benzene rings can be brominated. Thus pending aromatic bromine moieties can be used as the starting point for vulcanization.

6.2 Polymerization and Fabrication While almost all monomers bearing carbon-carbon double bonds may undergo radical polymerization, ionic polymerization is highly selective. This arises to some extent due to the stability of the propagating species. Cationic polymerization involves carbenium ions. In comparison to carbanions, which maintain a full octet of valence electrons, carbenium ions are deficient by two electrons and are much less stable. Therefore, the controlled cationic polymerization requires specialized systems. The instability or high reactivity of the carbenium ions facilitates undesirable side reactions such as bimolecular chain transfer to monomer, ß-proton elimination, and carbenium ion rearrangement. All of that limits the control over the cationic polymerization. Typically, low temperatures are necessary to suppress these reactions. Additionally, other considerations, such as stabilization of the propagating centers, use of additives to suppress ion-pair dissociation and undesirable protic initiation, and the use of high purity reagents to prevent the deactivation of the carbenium by heteroatomic nucleophiles are often required. However, by careful

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153

selection of the system, cationic polymerization can display living characteristics. Through these living cationic systems, cationic polymerization can be controlled to yield tailored polymers with narrow molecular weight distributions and precisely controlled molecular weight, micro-architecture, and end group functionality. Controlled cationic polymerizations are deemed to be achieved under conditions in which chain end termination is reversible and undesirable reactions, such as chain transfer and water-initiation are suppressed. A major advantage of living and quasi living polymerization is the opportunity for one-pot in situ functionalization of the polymer by reaction of the living chain ends with an appropriate quenching reagent. Living polymerizations refer to any polymerization during which propagation proceeds with the exclusion of termination and chain transfer and thus yields polymers retaining their ability to add further monomer whenever it is supplied to the system. With the advent of carbocationic living polymerization, there have been attempts to functionalize these living polymers. The extent of success of these attempts has been directly linked to the type of monomer being polymerized (5). Chain end functionalization of reactive carbocationic monomers, like isobutyl vinyl ether, can occur using ionic nucleophilic quenching reagents, i.e., methanol, alkyl lithium, etc. (6). However, chain end functionalization does not occur when these reagents are added to living polymerization of less reactive monomers such as isobutylene (7). The addition of these reagents at the end of the polymerization reaction resulted in the consumption of the catalyst and the formation of feri-alkyl chloride chain ends on the PIB rather than the desired nucleophilic substitution (5). Functionalization of quasi living PIB has been typically attempted through the use of functional initiators and through in situ functionalization by quenching. Most past efforts to produce functionality by quenching of quasi living chains have failed and led to tert-chloride terminal units (8). This is explained as quasi living PIB is composed primarily of dormant, i.e., reversibly terminated chains. Thus, most added reagents, particularly strong nucleophiles, quench the Lewis acid coinitiator

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and therefore yield only the ferf-chloride chain end. However, these groups are often undesirable as they tend to decompose and are liberating HCl, which is corrosive toward metal surfaces (5). 6.2.1

Catalyst

Systems

The polymerization of isobutylene using Friedel-Crafts type catalysts, including BF3 and related complexes, is a well-known procedure. The early reports on the polymerization use still boron trifluoride at subambient temperature as polymerization catalyst (1,9-11). The polymerization of α-olefins using Friedel-Crafts type catalysts is a cationic process, which proceeds through formation of intermediate carbonium ions (10). Catalyst systems with improved heat transfer capability for the production of PIB polymers in continuous slurry polymerization processes have been described. The catalyst consists of a Lewis acid, including Friedel-Crafts catalysts such as AICI3, and a tertiary halide containing compound, e.g., 2-chloro-2,4,4-trimethylpentane or ethylaluminum dichloride (12,13). 6.2.2

Polymerization

Techniques

6.2.3 PIB Grades PIB may be manufactured in at least two different major grades, namely (14), • Regular PIB and • High vinylidene PIB. These two product grades have been made by different processes, but both often and commonly use a diluted isobutylene feedstock in which the isobutylene concentration varies from 40-60%. However, at least the high vinylidene PIB type may be produced using a concentrated feedstock with an isobutylene content of 90%. Non-reactive hydrocarbons, such as isobutane, n-butane or other lower alkanes commonly present in petroleum fractions, may also be included in the feedstock as diluents. Further, the feedstock

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155

may contain small quantities of unsaturated hydrocarbons such as 1-butene or 2-butene (14). Regular grade PIB may range in molecular weight from 500 to 1,000,000 Dalton. These grades are generally prepared in a batch process at low temperature, down to -70°C. Suitable catalysts are AICI3 and organic derivatives thereof. Actually, the catalyst is not completely removed from the final polymer. The molecular weight may be controlled by the. temperature of the process. In general, higher temperatures result in lower molecular weights. The reaction times are usually in the range of hours. Ideally, at least 90% of the double bonds are within the backbone and less than 10% of the double bonds are in a terminal position (14). In contrast, high vinylidene PIB is characterized by a large percentage of terminal double bonds, typically greater than 70% and preferentially greater than 80%. This provides a much more reactive product, compared to regular PIB. For this reason, this product is referred to as highly reactive PIB. The terms highly reactive PIB and high vinylidene PIB are synonymous. High vinylidene PIB is produced using BF3 catalysts. Since the formation of the terminal double bonds is kinetically favored, short reactions times favor high amounts of vinylidene moieties. At a desired conversion, the reaction is quenched, usually with an aqueous base solution, such as, for example, NH4OH, before a significant isomerization into internal double bonds can take place. The molecular weights of high vinylidene PIB are comparatively low, i.e., in the range of 1 k Dalton (14). 6.2.4

Star Shaped Polymers

The synthesis of various multi-arm star polymers has long been of growing practical and theoretical interest to a variety of industries. Star polymers have shown to be useful as surfactants, lubricants, rheology modifiers, and viscosity modifiers. Actually, star polymers are considered as viscosity modifiers and oil additives (15). Star polymers may be synthesized in several ways. The arm-first method joins preformed arms together using a linking agent, and the core-first method utilizes a multifunctional initiator to grow the

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arms outward (16). Star polymers that bear at least two chemically different arm types are termed as miktoarm star polymers. Multifunctional initiators are suitable for the synthesis of miktoarm star polymers. This is achieved by combining different polymerization techniques, e.g., cationic, radical, etc., for each arm (17). The synthesis of A2B miktoarm star polymers has been discussed and exemplified using PIB as a component. The synthesis involves a quasi living cationic polymerization of isobutylene from a monofunctional cationic initiator. This initiator also contains a blocked hydroxyl group. Eventually, the blocked hydroxyl group of the initiator is deblocked, and functionalized with a branching agent. This activated reagent is then used for an atom transfer radical polymerization process of tert-butyl acrylate (18). The synthesis of higher order comb or star polymers with more than 20 PIB arms emanating from a core of condensed siloxanes, preferably cyclosiloxanes has been described (15). The stars are characterized by a combination of two symbols, the first of which indicates the number-average molecular weight (MM) of the arms, and the second the number of arms (N„). For example, 9K-4.4 designates a star having at average 4.4 PIB arms, each arm of M„ =9kDalton. 6.2.5

Grignota

Synthesis

See the discussion about the properties of polymers produced from unsymmetric monomers in section 6.3. Head to head (H-H) arrangements can be produced by special techniques of polymerization (19). In particular, H-H PIBs with molecular weights in the range of 3-10 k Dalton were prepared by the Grignard coupling polymerization of 2,2,3,3-tetramethyl-l,4-dibromobutane with copper(I) tris(triphenylphosphino)bromide as catalyst (20). This catalyst is also referred to as the Yamamoto catalyst (21). The reaction is sketched out in Figure 6.2. The polymers are crystalline, with a melting temperature of 187°C and a glass transition temperature of 87°C. In contrast, H-T PIB is a rubbery polymer, with a glass transition temperature of -61°C. Further, the polymer contains bromine end groups. As a side reaction, cyclization is observed.

Poly(isobutylene)

157

CH3 CH3 Br—H2C-C

C—CH2—Br

Cu(l).Br[(C 6 H 5 ) 3 P] 2

I

Mg,THF

OHq CH; *H2C-C

C — C H2

CHq CH'

Figure 6.2: Grignard Coupling Polymerization (19) Table 6.2: End Chain Functionalization End Groups References exo-Olefins Alkoxybenzenes Azides Pyrroles 1,1-Diphenylethylenes Thiophenes

(22) (23) (24) (25) (26,27) (28)

An alternative to produce H-H arranged PIB is the coupling via the Wurtz-Fittig reaction. This is the coupling of alkyl halides by the treatment with metallic sodium or other metals such as lithium and zinc. However, this type of reaction results in substantially branched polymers with a comparatively low molecular weight (19). 6.2.6

End Group

Functionalization

In the course of quasi living carbocationic isobutylene polymerization it is possible to functionalize the polymer at their end groups by quenching with reactive compounds. The various possibilities are shown in Table 6.2. The procedure of end chain quenching is very similar in all as-

158

Engineering Thermoplastics: Polyolefins and Styrenics

cl +

OOK

f

OC/T

[r)

N_(CH2)n cl

iN-(CH2)n-CI +

Figure 6.3:

~

TiCI.

" W

*(CH 2 ) n -CI

End Chain Quenching (25)

Table 6.3: Blends, Composites and Block Copolymers Type of Block Copolymers Poly(isobutylene)/Poly(methyl methacrylate) Poly(sryrene)/Poly(isobutylene)/Poly(styrene)) Poly(isobutylene)/Thermoplastic poly(urethane) Poly(isobutylene)/Pivolactone

References (29,30) (4,31,32) (33) (34)

pects. In Figure 6.3 the mechanism for pyrroles is shown (25). PIB polymers with halogen end groups can be functionalized as such with anhydrides. Chlorine functional oligomers can be heated in the presence of maleic anhydride (MA) without any catalyst. In a two step process, the chlorine end functional groups are at first converted by selective dehydrochlorination into isopropenyl end groups with potassium ferf-butylate. In the second step, MA is coupled to the PIB with unsaturated end groups. Eventually, the polymer can be reacted with difunctional amines to give an imide coupling (35). 6.2.7

Blends and Composites

Various blends, composites and block copolymers containing the isobutene moiety have been synthesized. The interest in these compounds originates from possible applications in advanced technologies. Polymers of these types are summarized in Table 6.3. PS/PIB/PS block copolymers can be made by controlled-living cationic polymerization. In this polymerization process, the propagating chains are in equilibrium with the dormant species. A suit-

Poly(isobutylene)

Ck

'CHs

H3

159

^

H,C

H3C

TiCI 4

Τ1ΌΙ4

Figure 6.4: Catalyst Systems for Controlled-Living Cationic Polymerization (4,36) able catalyst is l,3-bis(2-chloro-2-propyl)-5-ferf-butylbenzene/titanium tetrachloride (4). Several similar catalyst systems are suitable for this type of polymerization (36). Some systems are shown in Figure 6.4. Mixtures of titanium tetrachloride and boron trichloride as the inorganic coinitiator component give particularly high yields of polymer (36). PIB based thermoplastic poly(urethane)s (TPU)s have been synthesized. These composites exhibit enhanced mechanical properties. Poly(tetramethylene oxide) (PTMO) has been used as a compatibilizer. PIB based block copolymers are of interest for biomédical applications due to their superior biostability and biocompatibility (30). In biomédical applications, a typical TPU consists of PTMO as soft segment and diisocyanatodiphenyl methane as a hard segment. Further, 1,4-butanediol is used as a chain extender (37). PIB is well-known for its superior biostability and biocompatibility. Many copolymers based on PIB have been synthesized and studied in this aspect (38,39). A low molecular weight hydroxyallyl modified telechelic PIB was used as poly(alcohol) for the synthesis of the composites. Several procedures for the synthesis have been described involving two steps and as well as single step. The synthesis is schematically shown in Figure 6.5. The two step synthetic procedure is advantageous over the single step procedure to obtain processable polymers with high molecular

160

Engineering Thermoplastics: Polyolefins and Styrenics

O

HO'

OCN

"OH

-C^CH2~CI^ -ChV-U

))—NCO

HO'

A

A

O

O

O

Figure 6.5: Synthesis of a TPU Modified Telechelic PIB (33)

Poly(isobutylene)

161

weight. A series of PIB based TPUs synthesized in these ways have been characterized with respect to their mechanical properties (33). 6.2.8 Halogenation

Processes

Halogenated butyl rubbers have particularly advantageous adhesion behavior, flexural strength, service life and impermeability to air and water (40). The specific structure of the halogenated butyl rubber depends on the conditions of halogenation. Typical halogenation processes for making halobutyl rubbers involves the injection of chlorine or bromine into a solution of butyl rubber. The reactants are mixed vigorously in the halogenation reactor with a rather short resident time, typically less than 1 min, followed by the neutralization of the HC1 or HBr and removal of the unreacted halogen (13). The procedures of halogenation have been described in detail elsewhere (41,42). Alternatively the halogenation can be carried out in polymer melt in an extruder or other rubber mixing devices in the absence of solvent. The addition of an oxidizing agent, such as hydrogen peroxide, oxidizes the hydrogen halide generated in situ in the reaction back to free halogen (42) as 2HBr + H2O2 -* Br2 + 2H 2 0.

(6.1)

This regenerated halogen is thus available to further halogenate the butyl rubber, thereby increasing the halogenation utilization by as much as 70%. Another process for improving the bromination efficiency in rubber bromination processes is to conduct the reaction in the presence of elemental bromine and an aqueous solution of an organic azo compound such as 2,2'-azobisisobutyronitrile and sodium hypochlorite, potassium hypochlorite, or magnesium hypochlorite (42,43).

6.3

Properties

Saturated copolymer types are much more stable to atmospheric degradation than those with unsaturations, both in the backbone and in the side chains.

162

Engineering Thermoplastics: Polyolefins and Styrenics Table 6.4: Properties of PIB a (44) Property

Value

Density 0.92 Specific Heat (25°C) 2.0 Thermal Conductivity 0.19 Refractive index 1.51 Dielectric constant 2.2 Water permeability 2.5 10"7 a Opanol® (Series) BASF

Unit gem" 3 Jkg^K" 1 Wm^K" 1 kgm _1 h _1 bar _1

Properties of PIB are shown in Table 6.4. Unsymmetric monomers may form polymers that are in the form of head to tail (H-T) and head to head (H-H) arrangements. The H-T arrangement is most common. Mostly these variations in the arrangements are not important. However, as a specific example, it has been shown that in poly(vinyl chloride) the H-H and the H-T species are immiscible, whereas for PIB the H-H and the H-T species are miscible over a wide range of compositions (19). H-T PIB is a rubbery polymer. It has a glass transition temperature of -61°C. Further, it can be crystallized by mechanical stress. In contrast, H-H PIB has a glass transition temperature of 87°C and is a crystalline. This difference in the properties arises from the overall stiffness of the polymeric chains. Flory explained these differences in the properties by conformational energy considerations (45). In H-T PIB, the energy difference in changing the chain conformation is not pronounced. This causes the chain to become flexible. In contrast, H-H PIB exhibits a large rotation barrier around its adjacent dimethyl substituted carbon atoms. Thus, H-H PIB can not change its conformations, which results in a stiff and regular chain that is crystalline (19). 6.3.1

Mechanical

Properties

PIB types include a wide range of molecular weight. Low molecular weight grades appear as viscous oils. The viscosity increases with increasing molecular weight. High molecular weight exhibit a sticky appearance.

Poly(isobutylene)

163

6.3.1.1 Strain-induced Crystallization Certain polymers can be crystallized by mechanical stress. Namely, the stress induced elongation decreases the entropy of the chains. For this reason, an additional decrease in entropy, which is required for crystallization is comparatively small. Strain induced crystallization phenomena are of great practical importance since the elastomeric properties can be tailored in some way. In particular, PIB readily undergoes strain induced crystallization already close to room temperature. A change in crystallinity causes a change in the melting points of the polymers. The temperatures at which crystallization is observed at a certain elongation can be taken to be estimate the melting points of the samples. For PIB, the temperature range over which crystallization occurred is found to narrow considerably with an increase in elongation. At low elongations, the nominal melting points increase gradually with the increase in elongation. In contrast, at high elongations, the dependence on elongation becomes linear and more pronounced (46). 6.3.2

Thermal Properties

Fundamental studies on the thermal degradation of PIB have been done by Lehrle (47). In addition, a series of papers appeared by Sawaguchi and Seno. The thermal degradation starts around 350°C, as can be visualized from thermogravimetry experiments. The chain scission of PIB consists in a homolytic scission of the backbone with subsequent disproportionation or backbiting ^-rearrangement, as shown in Figure 6.6. It was found that the scission of terminal double bounds contributes to the thermal degradation much more than random scission (48). Thus, hydrogénation results in a markedly decrease of the kinetics of degradation. A secondary degradation reaction is the well-known ß-scission. The reactivity towards to jS-scission depends on the segmental motion of the reacting radicals (49-51). Degradation products containing ferf-butyl groups and /-propyl groups are obtained. The ratio of these two groups of products is roughly constant, when the molecular weight is above the molecular weight of a segment of the length of

164

Engineering Thermoplastics: Polyolefins and Styrenics

OH3 ^Ο

OH2

(-/·~'3 γ

ΟΗ2

^-''-'3

ΟΗ3

'Ç—CHo* * C - C H ,

¿H,

SH,

OH, ?-CH 3

Í

->Ho

♦+

Ç",

C-CHpV .

/

CH.-i

Figure 6.6: Primary Reactions of the Thermal Degradation of PIB (47) an entanglement, but changes otherwise with the molecular weight. This behavior is attributed to intramolecular backbiting. In the course of the depolymerization primary and tertiary terminal macroradicals are formed. A difference in the reactivity these radicals is explained by assuming that the jS-scission depends on the rotational energy barrier the terminal C-C- bond in the primary and tertiary terminal radicals (52). By controlled thermal degradation of PIB, end-reactive oligomers can be prepared (53). For example, the resulting end-reactive polymers having one or two tertiary chloro groups can be converted to terminal-unsaturated polymers bearing an isopropenyl group by dehydrochlorination For PIB, a method resulting in end-reactive polymers, however, based on chain transfer reactions during polymerization, was addressed as the cationic inifer method (54). 6.3.3 Electrical Properties PIB has a high electrical resistance in the order of 1014 Ω m. This property is advantageous for insulating applications. On the other

Poly(isobutylene)

165

Table 6.5: Permeation Coefficients of Selected Polyolefins (55) Permeation Coefficient/[cm2d ^bar1] Gas

Temperature °C

Nitrogen Nitrogen Oxygen Oxygen Carbon dioxide Carbon dioxide

20 40 20 40 20 40

Natural Rubber

Oppanol B200

LDPE

HDPE

3.9 12 13 30 73 150

0.13 0.5 0.6 1.9 2.6 6.9

0.7 2.0 1.8 6.0 8.0 23

0.10 0.31 0.45 1.4 -

hand, a cumulation of electric charges may occur, which may be a drawback. 6.3.4

Optical

Properties

PIB as such is not resistant against UV radiation. In order to increase the stability, appropriate additives must be added. In the simplest case, carbon black serves as UV-protective additive. 6.3.5

Gas Permeation

PIB exhibits a comparatively low gas permeation (56). In Table 6.5, gas permeation coefficients of some polyolefins are given. Oppanol® B 200 is compared with natural rubber, high density polyethylene) and low density poly(ethylene). Certain other Oppanol® types have roughly the same permeability to gases as Oppanol® B 200. The solubility of a gas is an integral part for the prediction of the permeation properties. Various models for the prediction of the solubility of gases in elastomeric polymers have been evaluated (57). Only a few models have been found to be suitable for predictive calculations. For this reason, a new model has been developed. This model is based on the entropie free volume activity coefficient model in combination with Hildebrand solubility parameters, which is commonly used for the theory of regular solutions. It has been demonstrated that mostly good results are obtained. An exception

266

Engineering Thermoplastics: Polyolefins and Styrenics

occurs, when semicrystalline polymers and polar gases are involved. The research is of practical interest for sealing applications. In the case of PIB, deviations from theory and measurement in the range of 4% are reported. 6.3.6

Chemical and Physical

Resistance

PIB is resistant against weak acids and bases, however, it is not resistant against halogens.

6.4

Special Additives

PIB is not resistant to weathering and must be stabilized with antioxdants. Suitable antioxidants are from the Irganox® series or from the Tinuvin® series. For medical applications, the antioxidant is selected from ascorbic acid, propyl gállate, butylhydroxyanisole, or dibutylhydroxytoluene (58). For hot melt pressure sensitive adhesive compositions for attaching roofing membranes the addition of flame retardants is desirable (59). The flame retardant is selected from brominated compounds, including decabromodiphenyl oxide, tetradecabromodiphenoxybenzene, hexabromocyclododecane, l,2-bis(pentabromophenyl)ethane, and ethylene bistetrabromophthalimide. Antimony trioxide is used as synergistic agent. These formulations may contain a compatible plasticizer. The plasticizer may also function as a tackifier and gives to the composition its softness and high initial adhesivity. Examples of suitable plasticizing agents include poly(butene)s, or chlorinated paraffins such as chlorowax.

6.5

Applications

Regular PIB may be used as a viscosity modifier, particularly in lube oils, as a thickener, and as a tackifier for plastic films and adhesives. PIB can also be functionalized to produce intermediates for the manufacture of detergents and dispersants for fuels and lube oils (14).

Poly(isobutylene) 6.5.1 Drag Reduction

167

Additives

Drag reduction is an important issue for the transportation of materials through pipelines. By introducing small amounts of a flexible polymer into a turbulent flow has been known to reduce the drag. Adding 10-50 ppm of a high molecular weight polymer to a turbulently flowing fluid in a pipe can result in a reduction of the drag by more than a 50% (60). This causes a significant reduction of the energy costs that are necessary to move the fluid. Drag reduction is caused by the viscoelasticity of polymer solutions (61). PIB is oil soluble and is thus interesting as a drag reducing additive for the transport of crude oil in pipelines (62). Universal drag reduction curves can be obtained in several ways, for example, by normalizing the hydrodynamic volume fraction of the polymer in solution (63). Further, a three-parameter empirical relationship between the drag reduction and concentration has been introduced (64). The effects of the concentration of PIB on drag reduction in different solvents have been investigated (65). Viscosity measurements of PIB with different molecular weights in two solvents, namely cyclohexane and xylene showed that a universal drag reduction equation can be used in order to describe the behavior. 6.5.2

Oil and Fuel Additives

Internal combustion engines operate under a wide range of temperatures including low temperature stop-and-go service as well as high temperature conditions produced by continuous high speed driving. Stop-and-go driving, particularly during cold, damp weather conditions, leads to the formation of a sludge in the crankcase and in the oil passages of a gasoline or a diesel engine. This sludge seriously limits the ability of the crankcase oil to effectively lubricate the engine. In addition, the sludge with its entrapped water tends to contribute to rust formation in the engine. These problems tend to be aggravated by the manufacturer's lubrication service recommendations, which specify extended oil drain intervals (66). Historically, the commercial functionalization of oil and fuel additive polymers has been a complex multi step process. However, commercial implementation of in situ functionalization could reduce

168

Engineering Thertnoplastics: Polyolefins and Styrenics

N—CH2-CH2—N—CH2—CH3

Figure 6.7: Poly(isobutenyl) succinimide the time, energy, and overall cost associated with the production of oil and fuel additives. For example, PIB-based oil dispersants are typically produced by first polymerizing isobutene to form an olefinterminated PIB, reacting the PIB with MA to form PIB/succinic anhydride, and then reacting this product with a poly(amine) to form a PIB/succinimide amine. In total, the dispersant requires three synthetics steps. Each stage requires separate reaction conditions and exhibits less than 100% yield. Conventional sludge dispersants for lubricating oils have been composed from poly(isobutenyl) succinimide. The basic structure of such a PIB type is shown in Figure 6.7. Improved variants include branched forms that are shown in Figure 6.8 (66). Various methods of synthesis have been described in detail in the literature (66-68). For example, MA is grafted to PIB in the presence of chlorine. In a second step, the imide is formed by the reaction with a poly (amine). The addition of alkylated phenothiazines, e.g., decylphenothiazine or tetradecylphenothiazine still improves the performance (67). Alkylated phenothiazines are synthesized by the reaction of an alkylated diphenylamine with elementary sulfur. The synthesis is shown in Figure 6.9. In addition, in fuel compositions or lubricating oil compositions, poly(isobutyl) N-substituted pyrrole compounds are particularly useful as a detergent-dispersants. The additives can be synthesized via a carbocationic polymerization (5). Other variants that are used in lubricating oils are sulfurized olefin compositions (69). An example for poly(isobutyl-l,2-dithiole-4-cyclopentene-3-thione) compounds is shown in Figure 6.10. The compositions are prepared by sulfurization of a highly re-

Poly(isobutylene)

*7\

ΚΧ ΛΛ Ö

Figure 6.8: Branched Poly(isobutenyl) succinimide (66)

R

R ^

^

COT T O

S,J,

¿Λά

Figure 6.9: Synthesis of Alkylated Phenothiazines (67)

"x# Figure 6.10: Sulfurized End Chain PIB (69)

169

170

Engineering Thermoplastics: Polyolefins and Styrenics

Table 6.6: Two-Cycle Engine Lubricating Oil Composition (70) Component Polyisobutenyl (M„ 1200) amine (ethylene diamine) (60 % active ingredient) Polyisobutenyl (M„ 950) succinimide dispersant (50% active ingredient) Cs-Cis Dialkyl fumarate/vinyl acetate pour depressant (40% active ingredient) Ci4 Dialkyl fumarate/vinyl acetate pour depressant (88% active ingredient) Poly(isobutylene) (M„ 950 ) Hydrocarbon solvent Mineral oil Sum

% w/w

% v/v

10.421

10.00

12.824

12.00

0.421

0.40

0.111

0.10

7.711 18.924 49.588

7.50 21.00 49.00

100

100

active PIB that contains at least 25% of a methylvinylidene isomer. Lubricating oil compositions can be conveniently prepared by blending the sulfurized product with an oil. The components may also be preblended as a concentrate with various other additives as a master batch (69). An improved two-cycle oil is a combination of poly(isobutylene) amine and a nitrogen containing dispersant (70). Poly(isobutylene) amine can be prepared by chlorination or hydroformylation of PIB, and subsequent amination with ethylene diamine or similar compounds. Eventually, poly(alkyleneamine)s are obtained by these procedures. These compounds are added in amounts of 6-7%. A two-cycle engine lubricating oil composition has typically a composition as given in Table 6.6. 6.5.3 Polymeric

Antioxidants

Both natural and synthetic rubbers are sensitive to oxidation by atmospheric oxygen. Therefore, antioxidants must be added in order to inhibit the oxidation of rubber by atmospheric oxygen. However, conventional antioxidants exhibit certain disadvantages, including their inherent volatility and the possibility of being leached by water or organic solvents. If the antioxidants are removed from the polymer during ordinary service time, a serious

Poly(isobutylene)

171

adverse effect with respect to ageing is observed. This obvious drawback can be circumvented by adding polymer bound antioxidants. Actually, polymer bound antioxidants are highly resistant to volatilization and leaching. However, the main disadvantage polymer bound antioxidants is their restricted mobility. On the other hand, if the antioxidant is bound to a low molecular weight polymer this problem is not as serious. There are two basic approaches to obtain polymeric antioxidants (71): 1. Copolymerization of monomers with an antioxidant active moiety with the elastomeric monomers, and 2. Modifying polymeric elastomers with a conventional antioxidant. A vinyl monomer that acts as an antioxidant is 4-anilino-N-(4vinylbenzyl)aniline, which can be prepared from p-aminodiphenylamine and p-chloromethylstyrene. Similarly, the reaction product of p-hydroxydiphenylamine and p-chloromethylstyrene, which is 4anilinophenyl-4-vinylbenzyl ether is useful in this way (72). The synthesis is shown in Figure 6.11. An example for the second type of polymer bound antioxidant is the bounding of p-phenylene diamine to a low molecular weight chlorinated PIB (71). For chlorination, PIB is dissolved in CCI4 and dry chlorine gas is passed through this solution. The chlorinated sample is isolated from the solution. In the second step of the preparation, the chlorinated sample is eventually dissolved in dioxan and mixed with p-phenylene diamine which is also dissolved in dioxan. It has been shown that the thus rubber bound antioxidant can reduce the amount of plasticizer required for compounding and that the ozone resistance of a vulcanízate containing a p-phenylene diamine modified PIB is superior to that of other vulcanizates (71). The alkylation is achieved using an acid activated clay catalyst (73). The reaction is performed in nitrogen atmosphere. Namely, nitrogen gas atmosphere or other inert gas atmospheres, in contrast to air gas atmosphere, suppress the formation of products that deactivate the clay catalyst.

172

Engineering Thermoplastics: Polyolefins and Styrenics

α^ιΏ H

NH2

CI—CH2

~Ό~\

H

H

C^H^MiH Figure 6.11: Synthesis of 4-Anilino-N-(4-vinylbenzyl)aniline and 4-Anilinophenyl-4-vinylbenzyl ether (72)

Poly(isobutylene) 6.5.4

173

Emulsifiers

6.5.4.1 Emulsifiers for Emulsion Explosives Ammonium nitrate explosives are the largest group among the explosives used. These explosives have widespread use, particularly in mining (74). An important group within the ammonium nitrate explosives are emulsion explosives, which consist essentially of a water-in-oil emulsion of an aqueous solution, supersaturated at room temperature, in an oil matrix which is a fuel. The oil phase is the continuous phase and includes small droplets of the supersaturated solution of the oxidizing agent. The dissolved salts in the aqueous solution are metastable and have a tendency toward crystallization. If the ammonium nitrate is forming crystals unfavorable effects on the emulsion emerge, such as solidification. Then the emulsion is no longer pumpable. In addition, the cap sensitivity of the emulsion decreases. The cap sensitivity is the sensitivity of an explosive to initiation by a detonator. Thus, the explosive becomes less sensitive to initial detonation. Therefore, in order to keep such an emulsion stable, an emulsifier is generally required, which is suitable for the preparation of water-in-oil emulsions. Because of its surface activity, the emulsifier promotes the emulsification of the salt phase in small droplets and prevents the coalescence of the formed droplets after the emulsion has formed. The emulsion, also addressed as matrix, is generally still not ignitable. Therefore, in order to achieve sufficient cap sensitivity, the density of the matrix must be lowered by adding glass microspheres, by chemical gassing, or by adding granular ammonium nitrate. The emulsions are then in some circumstances also ignitable without boosters with blasting caps. Such emulsions are addressed as safety explosives (74). Some emulsifier formulations for explosives are summarized in Table 6.7.

274

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Table 6.7: Emulsifier Systems for Explosives Emulsifier Formulation Copolymers of poly(isobutylene) and maleic anhydride, functionalized with amines or amino alcohols Copolymers of poly(isobutylene), vinyl esters, and maleic anhydride Sorbitan ester, fatty acid glycerides or phosphoric esters Reaction products of poly(isobutenyl)succinic anhydride with amino alcohols, amines and sorbitol Reaction products of poly(isobutenyl)succinic anhydrides with morpholine and amino alcohols Polymers of poly(isobutylene) and maleic anhydride Terpolymers of poly(isobutylene), α-oleñns and maleic anhydride

Reference (74) (75) (76) (77) (78) (79) (80)

6.5.5 Chewing Gums A classical application of PIB is a chewing gum. There are still innovations in this topic. Chewing gum base compositions that produce gum bases and chewing gums having reduced adhesion to outdoor surfaces as compared to typical chewing gum compositions have been recently developed (81). When chewing gum is chewed, an insoluble portion remains. Although the remaining insoluble portion can be easily disposed of without creating any problems, when improperly disposed of, can create a nuisance. Due to their typical formulation, chewing gums have an adhesive-like characteristic. Therefore, the chewed gum can stick to outdoor surfaces onto which they are intentionally or unintentionally placed. Such surfaces can include concrete, flooring materials, walls, carpeting, metal, wood, plastic, glass and other surfaces. It is because of these circumstances that there is a consumer demand for a more removable chewing gum. Formulating an acceptable removable chewing gum cud has significant challenges in that, the product has to remain organoleptically desirable for the consumer, while being removable. Furthermore, the ingredients and processing of the gum base and chewing gums must be sufficiently inexpensive to permit commercial manufacture and sale at prices competitive with traditional formulations. All ingredients used must be safe for human consumption and ide-

Poly(isobutylene)

175

Table 6.8: Chewing Gum Base Compositions (81) Ingredient

Conventional

Terpene Resin Poly(vinyl acetate) (Mu,: 12-15 kDalton) Hydrogenated vegetable oil Mono- and diglycerides High Mu, poly(isobutylene) Poly(isobutylene) (Mw: 75 k Dalton) Butyl rubber Amorphous silica (25% H2O) BHA Calcium carbonate Lecithin Total

New

25.25 27.50 15.54 4.78 1.86 9.97 0.07 11.31 3.72

28.93 33.85 16.25 5.54 8.15 2.04 4.65 0.05 0.54 -

100.00

100.00

ally are already approved for food use (81). There have been attempts in the past to formulate removable chewing gum bases and chewing gum compositions. For example, a non-stick chewing gum may contain a blend of different molecular weight poly(vinyl acetate), filler, non-elastomer solvent resin, and is essentially free of fats and waxes (82). In Table 6.8 a chewing gum cud formulation is given, which can be easily removed from surfaces. 6.5.6 Medical 6.5.6.1

Applications

Stents

PS/PIB/PS block copolymers have been shown to be vascularly compatible. When loaded with paclitaxel and coated on a coronary stent, the composite can deliver the drug directly to arterial walls. 6.5.6.2

Drug Release

Modulation of the drug release behavior from this polymer can be achieved by varying the drug/polymer ratio, by blending the basic block copolymer with other polymers, and by derivatizing the styrene end blocks. In this way, the hydrophilicity of the copolymer is varied (27).

376

Engineering Thermoplastics: Polyolefins and Styrenics

6.5.7 Pressure Sensitive

Adhesives

Pressure sensitive adhesive have been known for a long time. However, the combination of PIB and silicone components is a more recent development. Silicone functionalized PIB is particularly suitable as a pressure sensitive adhesive composition in medical applications including transdermal drug delivery applications (83). The preparation proceeds in the following way: A telechelic alcohol-functional PIB is first reacted with butyllithium in order to form an alcoholate-functional PIB dianion and the latter is then reacted with hexamethylcyclotrisiloxane to generate a living poly(dimethylsiloxane) chain at the end groups of the PIB. In a final step, the remaining anionic ends are capped with trimethylchlorosilane or dimethyldichlorosilane. In this way a block copolymer, is obtained. The pressure sensitive adhesive exhibits (83): 1. Biocompatibility to the skin, 2. Hot-meltable processing, 3. The possibility of modifying the properties of the pressure sensitive adhesive, such as drug permeability, solubility, adhesiveness, releasibility, and tackiness, and 4. Making the pressure sensitive adhesive either transparent or white resulting in an aesthetically-pleasing product. The above described pressure sensitive adhesive compositions are especially suitable for assisting in delivering a bioactive agent, such as a drug to a bioactive-agent-accepting substrate, i.e., the patient's skin. The pressure sensitive adhesive composition may be employed in three modes of bioactive agent delivery (83). The first mode is by incorporating the bioactive agent in the pressure sensitive adhesive composition, which is thereafter attached to the substrate to commence delivery. The second mode of delivery is by attaching a membrane of the pressure sensitive adhesive composition to the substrate and contacting a reservoir or matrix including a bioactive agent to the attached membrane. The bioactive agent may then pass from the reservoir or matrix through the attached membrane and to the substrate for absorption.

Poly(isobutylene)

177

Table 6.9: Examples for Commercially Available PIB Polymers Tradename

Producer

Remarks

Dynapak Glissopal®

Univar BASF

Himol

Nippon Petrochemicals

Isobam®

Kuraray

Lubrizol PIB Oppanol® Permethyl

Lubrizol BASF Presperse Comp.

Tekol Tetrax Vistanex®

Kraiburg TPE GmbH Nippon Petrochemicals ExxonMobil

Low molecular weight PIB Low molecular weight, high reactive PIB Medical adhesive material, chewing gum base ingredient Poly(isobutene-co-maleic anhydride) resins Lubricant additive Various grades Release agent, component in cosmetic agents Lubricant improver

The third mode of delivery is accomplished by applying pressure sensitive adhesive to the perimeter of a delivery device having a bioactive-agent-containing matrix in the center. The delivery device is then attached to the substrate and the bioactive-agent-containing matrix contacts the substrate directly.

6.6

Suppliers and Commercial Grades

Examples for commercially available PIB polymers and suppliers as well are shown in Table 6.9. Tradenames appearing in the references are shown in Table 6.10.

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Table 6.10: Tradenames in References Tradename Description

Supplier

AgeRite™ Resin D Vanderbilt Antioxidant (13) Budene® 1207 Goodyear Tire & Rubber Co. Poly(butadiene), 98% cis-1,4 (13) Exxon Bromobutyl™ 2222 ExxonMobil Brominated copolymer of isobutylene and isoprene (13) Exxpro™ ExxonMobil Brominated isobutylene p-methylstyrene copolymer (13) FLEXON™ ExxonMobil Paraffinic process oil (13) Fulcat™ Laporte Montorillonit based catalyst (73) Glissopal® 1000 BASF Poly(isobutene) (75) HPA™ X Dow Heavy polyamine (68) Igepal® Rhone-Poulenc Al ky lphenoxypoly(ethylenoxy )ethanol (42) Irganox® 1010 Ciba Geigy Pentaerythritol tetrakis(3-(3,5-di-ierf-butyl-4-hydroxyphenyl)propionate), phenolic antioxidant (40,41) Irganox® L57 Ciba Octylated/butylated diphenylamine (73) KADOX™ 930C Zinc Corp. of America Zinc oxide, curing agent (13) Natsyn™ 2200 Goodyear Poly(isoprene) (13) Naugalube® 640 Chemtura Corp. (Crompton) Octylated, butylated diphenylamine antioxidant (73) Retrol® Filtrol Comp. of California Acid-activated clay (73) Santoflex® 13 Monsanto N-( 1,3-Dimethy lbuty \)-N' -phenyl-p-pheny lenediamine, antioxidant (13) Sucralose® McNeil Nutritionals Chlorodeoxysucrose derívate, artificial sweetener (82)

Poly(isobutylene)

179

Table 6.10 (cont): Tradenames in References Tradename Description

Supplier

Sundex™ Sun Chemicals Rubber processing aid , aromatic oil (13) Ultra vis® British Petroleum Comp. Poly(butene) based additives (74,75) Vistalon™ 7800 Exxon Mobil Poly(olefin) (13) Viton® (Series) DuPont Fluoropolymer (68) Zeosil® Rhodia Inc. Silica (13)

6.7 Environmental Impact and Recycling PIB is considered as nontoxic. Nevertheless, a severe accident has been reported (84). In December 1998 a mass stranding of seabirds at the North Sea coast was observed. The birds were covered in a whitish, sticky substance. This substance was identified as PIB. It has been suspected that the PIB has been dumped into the sea from a ship.

References 1. M. Otto and M. Müller-Cunradi, Verfahren zur Darstellung von hochmolekularen Kohlenwasserstoffen aus Isobutylen, DE Patent 641 284, assigned to IG Farbenindustrie AG, January 27,1937. 2. M. Otto and M. Müller-Cunradi, High molecular weight iso-olefine polymers and process of producing the same, US Patent 2130507, assigned to IG Farbenindustrie AG, September 20,1938. 3. T. Kessel, 75 Jahre Oppanol®: Erfolgreiche Vergangenheit, vielversprechende Zukunft, Press Information P 426/06, BASF Aktiengesellschaft, Ludwigshafen, Germany, 2006. [electronic:] http://www.veredlungschemikalien.basf.de/ev-wcms-in/ internet/de_DE/function/conversions:/publish/upload/pr/2006/ 061006-ev3-P426.pdf. 4. R.F. Storey, D.W. Baugh, and K.R. Choate, Poly(styrene-b-isobutylene-b-styrene) block copolymers produced by living cationic polymer-

180

Engineering

Thermoplastics:

Polyolefins

and

Styrenics

ization: I. Compositional analysis, Polymer, 40(ll):3083-3090, May 1999. 5. C D . Stokes, R.F. Storey, and J.J. Harrison, Process for preparing terminally functionalized living and quasiliving cationic telechelic polymers, US Patent 7 576161, assigned to Chevron Oronite Company LLC (San Ramon, CA) and The University of Southern Mississippi (Hattiesburg, MS), August 18,2009. 6. M. Sawamoto, T. Enoki, and T. Higashimura, End-functionalized polymers by living cationic polymerization. 1. Mono- and bifunctional poly(vinyl ethers) with terminal malonate or carboxyl groups, Macromolecules, 20(l):l-6, January 1987. 7. Y.C. Bae, Z. Fodor, and R. Faust, Living coupling reaction in living cationic polymerization. 1. Coupling reaction of living polyisobutylene, Macromolecules, 30(2): 198-203, January 1997. 8. R. Faust and J.P. Kennedy, Living carbocationic polymerization. XXI, Kinetic and mechanistic studies of isobutylene polymerization initiated by trimethylpentyl esters of different acids, /. Macromol. Sci.-Chem., 27(6):649-667,1990. 9. P. Boerzel, K. Bronstert, and F. Hovemann, Polyisobutenes, US Patent 4152499, assigned to BASF Aktiengesellschaft (DE), May 1,1979. 10. J.N.R. Samson, Cationic polymerization of 1-olefins, US Patent 4 605 808, assigned to BP Chemicals Limited (London, GB2), August 12,1986. 11. H.P. Rath, H. Hoffmann, P. Reuter, and H. Mach, Preparation of polyisobutene, US Patent 5191044, assigned to BASF Aktiengesellschaft (Ludwigshafen, DE), March 2,1993. 12. R.N. Webb, M.F. McDonald, D.Y.-L. Chung, Y.-J. Chen, R.D. Hembree, and J.P. Soisson, Process for polymerizing cationically polymerizable monomers, US Patent 6858690, assigned to ExxonMobil Chemical Patents Inc. (Houston, TX), February 22,2005. 13. W.H. Waddell and D.Y.-L. Chung, Elastomeric compositions, US Patent 7329 697, assigned to ExxonMobil Chemical Patents Inc. (Houston, TX), February 12, 2008. 14. C.E. Baxter, Jr., G. Valdez, C. Lobue, T. Lowry, and A. Abazajian, Midrange vinylidene content poly isobutylene polymer product produced by liquid phase polymerization process, US Patent 7498396, assigned to Texas Petrochemicals LP (Houston, TX), March 3, 2009. 15. J.P. Kennedy, N. Omura, and A. Lubnin, Higher order star polymers having multiple polyisobutylene arms radiating from a condensed core of siloxanes and a method for the synthesis thereof, US Patent 5 856 392, assigned to The University of Akron (Akron, OH), January 5,1999.

Poly(isobutylene)

181

16. N. Hadjichristidis, M. Pitsikalis, S. Pispas, and H. Iatrou, Polymers with complex architecture by living anionic polymerization, Chem. Rev., 101(12):3747-3792, 2001. 17. K.V. Bernaerts and F.E. Du Prez, Dual/heterofunctional initiators for the combination of mechanistically distinct polymerization techniques, Prog. Polym. Set., 31(8):671-722, August 2006. 18. L.K. Breland and R.F. Storey, Polyisobutylene-based miktoarm star polymers via a combination of carbocationic and atom transfer radical polymerizations, Polymer, 49(5):1154-1163, March 2008. 19. O. Vogl, M.F. Qin, and A. Zilkha, Head to head polymers, Prog. Polym. Sei., 24(10):1481-1525, December 1999. 20. M. Malanga and O. Vogl, Head-to-head polymers. XXIV. Synthesis of head-to-head polyisobutylene by grignard coupling reaction, /. Polym. Set., Part A: Polym. Chem., 21(9):2629-2648,1983. 21. T. Yamamoto, Y. Hayashi, and A. Yamamoto, A novel type of polycondensation utilizing transition metal-catalyzed C-C coupling. I. Preparation of thermostable polyphenylene type polymers, Bull. Chem. Soc. Jpn., 51(7):2091-2097, July 1978. 22. K.L. Simison, C D . Stokes, JJ. Harrison, and R.F. Storey, End-quenching of quasiliving carbocationic isobutylene polymerization with hindered bases: Quantitative formation of exo-olefin-terminated polyisobutylene, Macromolecules, 39(7):2481-2487, April 2006. 23. D.L. Morgan and R.F. Storey, End-quenching of quasi-living isobutylene polymerizations with alkoxybenzene compounds, Macromolecules, 42(18):6844-6847, September 2009. 24. H. Cheradame, J. Habimana de la Croix, E. Rousset, and FJ. Chen, Synthesis of polymers containing pseudohalide groups by cationic polymerization. 9. Azido end-capped poly(2-methylpropene) by polymerization initiated by the system lewis acid-2-azido-2-phenylpropane, Macromolecules, 27(3):631-637, January 1994. 25. N. Martinez-Castro, D.L. Morgan, and R.F. Storey, Primary halide-terminated polyisobutylene: End-quenching of quasiliving carbocationic polymerization with N-(/<>-haloalkyl)pyrrole, Macromolecules, 42(14): 4963-4971, July 2009. 26. H. Schlaad, K. Erentova, R. Faust, B. Charleux, M. Moreau, J.-P. Vairon, and H. Mayr, Kinetic study on the capping reaction of living polyisobutylene with 1,1-diphenylethylene. 1. Effect of temperature and comparison to the model compound 2-chloro-2,4,4-trimethylpentane, Macromolecules, 31(23):8058-8062, November 1998. 27. J.C. Cho, G. Cheng, D. Feng, R. Faust, R. Richard, M. Schwarz, K. Chan, and M. Boden, Synthesis, characterization, properties, and drug release of poly(alkyl methacrylate-b-isobutylene-fr-alkyl methacrylate), Biomacromolecules, 7(ll):2997-3007, November 2006.

182

Engineering Thermoplastics:

Polyolefins

and

Styrenics

28. N. Martinez-Castro, M.G. Lanzendorfer, A.H.E. Müller, J.C. Cho, M.H. Acar, and R. Faust, Polyisobutylene stars and polyisobutyleneblock-poly(tert-butyl methacrylate) block copolymers by site transformation of thiophene end-capped polyisobutylene chain ends, Macromolecides, 36(19):6985-6994, September 2003. 29. T. Higashihara, D. Feng, and R. Faust, Synthesis of poly(isobutyleneblock-methyl methacrylate) by a novel coupling approach, Macromolecules, 39(16):5275-5279, August 2006. 30. D. Feng, T. Higashihara, and R. Faust, Facile synthesis of diphenylethylene end-functional polyisobutylene and its applications for the synthesis of block copolymers containing poly(methacrylate)s, Polymer, 49(2):386-393, January 2008. 31. R.F. Storey, B.J. Chisholm, and M.A. Masse, Morphology and physical properties of poly(styrene-iMsobutylene-b-styrene) block copolymers, Polymer, 37(14):2925-2938, July 1996. 32. Z. Fodor and R. Faust, Polyisobutylene-based thermoplastic elastomers. IV. Synthesis of poly (styrene-block-isobutylene-block-styrene) triblock copolymers using n-butyl chloride as solvent, /. Macromol. Sci.-Chem., 33(3):305-324, March 1996. 33. U. Ojha, P. Kulkarni, and R. Faust, Syntheses and characterization of novel biostable polyisobutylene based thermoplastic polyurethanes, Polymer, 50(15):3448-3457, July 2009. 34. Y. Kwon, R. Faust, C.X. Chen, and E.L. Thomas, Synthesis and characterization of poly(isobutylene-f>-pivalolactone) diblock and poly(pivalolactone-b-isobutylene-b-pivalolactone) triblock copolymers, Macromolecules, 35(9):3348-3357, April 2002. 35. E. Walch and R. Gaymans, Telechelic polyisobutylene with unsaturated end groups and with anhydride end groups, Polymer, 35(8): 1774-1778, April 1994. 36. J. Feldthusen, B. Iván, A.H.E. Müller, and J. Kops, Synthesis of linear and three-arm star tert-chlorine-telechelic polyisobutylenes by a twostep conventional laboratory process, Macromol. Rapid Commun., 18(5): 417-^25,1997. 37. N.M.K. Lamba, K.A. Woodhouse, and S.L. Cooper, Polyurethanes in Biomédical Applications, CRC Press, Boca Raton, FL, updated edition, 1998. 38. S.J. Taylor, R.F. Storey, J.G. Kopchick, and K.A. Mauritz, Poly[(styrene-co-p-methylstyrene)-b-isobutylene-% textitb-(styrene-co-/?-methylstyrene)] triblock copolymers. 1. synthesis and characterization, Polymer, 45(14):4719-4730, June 2004. 39. J. Cho, G. Cheng, D. Feng, R. Faust, R. Richard, M. Schwarz, K. Chan, and M. Boden, Synthesis, characterization, properties, and drug re-

Poly (isobutylene)

40. 41. 42. 43. 44.

45. 46. 47.

48. 49. 50.

51. 52.

183

lease of poly (alkyl methacrylate-b-isobutylene-b-alkyl methacrylate), Biomacromolecules, 8(7):2336-3007, November 2007. G. Kaszas, Halogenated terpolymers of isobutylene, diolefin monomer and styrenic monomer, US Patent 6960632, assigned to Bayer Inc. (Sarnia, CA), November 1, 2005. G. Kaszas, Halogenated terpolymers of isobutylene, diolefin monomer and styrenic monomer, US Patent 7 402 633, assigned to Lanxess Inc. (Sarnia, Ontario, CA), July 22,2008. N.F. Newman, Process for halogenating isomonoolefin copolymers, US Patent 5 681901, assigned to Exxon Chemical Patents Inc. (Houston, TX), October 28,1997. W. Baade, H. Königshofen, and G. Kaszas, Process for the bromination of alkyl rubbers, US Patent 5569 723, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), October 29,1996. Bedwick, BASF Oppanol's Polyisobutylenes, Product Information N-EVON-3-2005, BASF Corporation, Florham Park, NJ 07932, 2005. [electronic:] http://www2.basf.us/pib_derivatives/pdfs/NLPF_ brochure.pdf. P.J. Flory, Statistical Mechanics of Clwin Molecules, Interscience Publ., New York, 1969. P. Xu and J.E. Mark, Strain-induced crystallization in elongated polyisobutylene elastomers, Polym. Gels Netw., 3(3):255-266,1995. M.R. Grimbley and R.S. Lehrle, The degradation mechanism of polyisobutylene: Part 2. characterisation of the products and the dependence of their yields on sample thickness provides detailed mechanistic information, Polym. Degrad. Stab., 48(3):441^55,1995. T. Sawaguchi and M. Seno, Thermal degradation of polyisobutylene: effect of end initiation from terminal double bonds, Polym. Degrad. Stab., 54(l):33-48, October 1996. T. Sawaguchi and M. Seno, Detailed mechanism and molecular weight dependence of thermal degradation of polyisobutylene, Polymer, 37 (25):5607-5617,1996. T. Sawaguchi, T. Ikemura, and M. Seno, Effect of molecular weight on formation of non-volatile oligomers by thermal degradation of polyisobutylene and its kinetic analysis, Polymer, 37(24):5411-5420, November 1996. T. Sawaguchi and M. Seno, Effects of the molecular weight of molecular chains constituting the reaction medium on the thermal degradation of polyisobutylene, Polymer, 39(18):4249-4259,1998. T. Sawaguchi and M. Seno, Thermal degradation of polyisobutylene: effect of rotational motion around C—G bond on the ß-scission leading to monomer formation, Polym. Degrad. Stab., 54(l):23-32, October 1996.

184

Engineering Thermoplastics:

Polyolefins

and

Styrenics

53. T. Sawaguchi and M. Seno, Preparation and characterization of end-reactive oligomers by thermal degradation of polyisobutylene, Polymer, 37(16):3697-3706, August 1996. 54. J.P. Kennedy and R.A. Smith, New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). II. Synthesis and characterization of a, a>-di(ferf-chloro)polyisobutylenes, /. Polym. Sei., Part A: Polym. Chem., 18(5):1523-1537,1980. 55. Anonymous, Oppanol® B 100 Oppanol® B 150 Oppanol® B 200, Technical Information TI/ES 1417 US, BASF Aktiengesellschaft, Ludwigshafen, Germany, 2003. [electronic:] http://www2.basf.us/pib_derivatives/pdfs/High_ Oppanol_B100_B150_B200.pdf. 56. L.K. Massey, "Polyisobutylene rubber," in Permeability Properties of Plastics and Elastomers: A Guide to Packaging and Barrier Materials, chapter 80, p. 469. William Andrew Publishing, Norwich, NY, 2nd edition, 2003. 57. P. Thorlaksen, J. Abildskov, and G.M. Kontogeorgis, Prediction of gas solubilities in elastomeric polymers for the design of thermopane windows, Fluid Phase Equilib., 211(l):17-33, August 2003. 58. Y. Takada, K. Tanaka, and Y. Ikeura, Plaster containing felbinac, US Patent 6 844 007, assigned to Hisamitsu Pharmaceutical Co., Ltd. (Saga, JP), January 18, 2005. 59. D.K. Fisher, Hot melt pressure sensitive adhesive composition for attaching roofing membranes, US Patent 6794449, assigned to Adco Products, Inc. (Michigan Center, MI), September 21, 2004. 60. A. Gyr and H.-W. Bewersdorff, Drag Reduction of Turbulent Flows by Additives, Vol. 32 of Fluid Mechanics and its Applications, Kluwer Academic Publishers, Dordrecht, 1995. 61. M.S. Jhon, G. Sekhon, and R. Armstrong, The response of polymer molecules in a flow, Adv. Chem. Phys., 66:153-211,1987. 62. E.D. Burger, L.G. Chorn, and T.K. Perkins, Studies of drag reduction conducted over a broad range of pipeline conditions when flowing Prudhoe Bay crude oil, /. Rheol, 24(5):603-626, October 1980. 63. C.L. McCormick, R.D. Hester, S.E. Morgan, and A.M. Safieddine, Water-soluble copolymers. 30. Effects of molecular structure on drag reduction efficiency, Macromolecules, 23(8):2124-2131, April 1990. 64. H.J. Choi and M.S. Jhon, Polymer-induced turbulent drag reduction, Industrial & Engineering Chemistry Research, 35(9):2993-2998, January 1996. 65. H.J. Choi, C.A. Kim, and M.S. Jhon, Universal drag reduction characteristics of polyisobutylene in a rotating disk apparatus, Polymer, 40 (16):4527-4530, July 1999.

Poly(isobutylene)

185

66. C.S. Liu, C.A. Migdal, N.R. Crawford, and R.I. Yamamota, Polyisobutylene succinimide and ethylene-propylene succinimide synergistic additives for lubricating oils compositions, US Patent 6117825, assigned to Ethyl Corporation (Richmond, VA), September 12, 2000. 67. C.K. Esche, Jr., C.A. Migdal, J.R. Sanderson, and A.L. Ippolito, Polyisobutylene succinimide, ethylene-propylene succinimide and an alkylated phenothiazine additive for lubricating oil compositions, US Patent 5 614124, assigned to Ethyl Additives Corporation (Richmond, VA), March 25,1997. 68. CF. Stachew, G.D. Lamb, W.D. Abraham, and M.G. Raguz, Modified polyisobutylene succinimide dispersants having improved seal, sludge, and deposit performance, US Patent 6 770 605, assigned to The Lubrizol Corporation (Wickliffe, OH), August 3, 2004. 69. K.D. Nelson and F. Plavac, Sulfurized polyisobutylene based wear and oxidation inhibitors, US Patent 7414013, assigned to Chevron Oronite Company LLC (San Ramon, CA), August 19, 2008. 70. E.J. Meny and RJ. Hartley, Two-cycle lubricating oil containing polyisobutylene amine, US Patent 6498129, assigned to Exxon Chemical Patents INC. (DE), December 24, 2002. 71. P.B. Sulekha, R. Joseph, and K.E. George, Studies on polyisobutylene bound paraphenylene diamine antioxidant in natural rubber, Polym. Degrad. Stab., 63(2):225-230, February 1999. 72. M. Tamura, T. Ohishi, and H. Sakurai, Diphenylamine derivatives and degradation inhibitors for rubber polymers, US Patent 4 298 522, assigned to Nippon Zeon Co. Ltd. (Tokyo, JP), November 3,1981. 73. A. Onopchenko, Alkylation of diphenylamine with polyisobutylene oligomers, US Patent 6355839, assigned to Chevron U.S.A., Inc. (San Ramon, CA), March 12, 2002. 74. P. Klug and R. Bender, Explosives comprising modified copolymers of polyisobutylene and maleic anhydride as emulsifiers, US Patent 6 719 861, assigned to Clariant GmbH (Frankfurt, DE), April 13, 2004. 75. P. Klug and R. Bender, Explosives comprising modified copolymers of polyisobutylene, vinyl esters and maleic anhydride as emulsifiers, US Patent 6 527885, assigned to Clariant GmbH (Frankfurt, DE), March 4, 2003. 76. H.F. Bluhm, Ammonium nitrate emulsion blasting agent and method of preparing same, US Patent 3447978, assigned to Atlas Chem. Ind., June 03,1969. 77. J. Cooper and A.S. Baker, Emulsion explosives composition, EP Patent 0155 800, assigned to ICI Pic, September 25,1985. 78. J.W. Forsberg, Water-in-oil emulsions, EP Patent 0 285 608, assigned to Lubrizol Corp., October 12,1988.

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Thermoplastics:

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79. J.J. Harrison, Novel polymeric dispersants having alternating polyalkylene and succinic groups, WO Patent 9 003 359, assigned to Chevron Res., April 05,1990. 80. J.J. Harrison and J. Ruhe, William R., Dispersant polysuccinimides derived from terpolymers, EP Patent 0 831104, assigned to Chevron Chem. Co., March 25,1998. 81. D. Phillips, C. Shen, M. Reed, and M. Patel, Chewing gum base and chewing gum compositions, US Patent 6986907, assigned to Wm. Wrigley Jr. Company (Chicago, IL), January 17,2006. 82. G. Mansukhani, J.J. Kiefer, and N. D'Ottavio, Non-stick chewing gum, US Patent 5 601858, assigned to Warner-Lambert Company (Morris Plains, NJ), February 11,1997. 83. PW. Pretzer and R.P. Sweet, Silicone pressure sensitive adhesive composition containing functionalized polyisobutylene, US Patent 5 939 477, assigned to Dow Corning Corporation (Midland, MI), August 17,1999. 84. K.C.J. Camphuysen, H. Barreveld, G. Dahlmann, and J.A. van Franeker, Seabirds in the North Sea demobilized and killed by polyisobutylene (C 4 H 8 ) n (PIB), Mar. Pollut. Bull, 38(12):1171-1176, December 1999.

7

Ethylene Vinyl Acetate Copolymers Ethylene vinyl acetate (EVA) is a copolymer from ethene and vinyl acetate. Several variants of this type are known and described in this chapter.

7.1

Monomers

Monomers used are shown in Table 7.1 and in Figure 7.1. Basically, all monomers that are copolymerizable with ethene and vinyl acetate also may be used together with ethylene and vinyl acetate. Such monomers include (1): 1. 2. 3. 4.

a-Olefins, Unsaturated acids, Nitriles, and Amides.

O // v

Ethene

O-CH=CH2

Vinyl acetate

Figure 7.1: Monomers used for EVA 187

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Engineering Thermoplastics: Polyolefins and Styrentcs

Table 7.1: Monomers for EVA (1) Monomer

Remarks

Ethene Vinyl acetate Propene Isobutene 1-Octene Acrylic acid Methacrylic acid Crotonic acid Maleic acid Itaconic acid Acrylonitrile N-methylol acrylamide Acrylamide Ethylene sulfonic acid Allyl sulfonic acid Versatic acid vinyl esters Vinyl ethers N-Vinylpyrrolidone Vinyl chloride Vinylidene chloride

Basic momomer Basic momomer

Adhesion Adhesion Adhesion Adhesion Adhesion

promoters (2) promoters (2) promoters (2) promoters (2) promoters (2)

Crosslinker (3) Semicrystalline polymers (2) Semicrystalline polymers (2)

Ethylene Vinyl Acetate Copolytners 7.1.1

189

Vinyl Acetate

Vinyl acetate is produced by the oxidation of ethylene and acetic acid (4,5). Catalysts for the gas phase oxidation are made from palladium compounds with additional metal compounds on a porous support (6). Catalysts, preferably coated catalysts, can be used for many heterogeneously catalyzed reactions such as hydrogénations and oxidations. Among other things, P d - A u coated catalysts are extremely well suited to the catalysis of the gas phase oxidation of ethylene and acetic acid to give vinyl acetate. The catalytically active metals are deposited in the form of a shell on or in the outermost layer of the support. They are often produced by penetration of the support with metal salts into a surface region and subsequent precipitation by alkalis to form water insoluble P d - A u compounds (5). Conventionally, a fixed bed catalyst containing palladium, a promoter metal, and an alkali metal acetate is used. The fixed bed catalyst components are supported on a porous carrier such as silica, zirconia or alumina. A fluid bed process for oxyacylation of olefins has been described (4). The fluid bed process overcomes some of the disadvantages in the fixed bed operation to produce vinyl acetate. In the fluid bed process the catalyst is continuously homogeneously mixed in the reactor resulting in a significant improvement in the homogeneous addition of the promoter even if it is introduced through a single outlet. The fluid bed operation allows the continuous removal of a portion of deactivated catalyst and continuous replacement of catalyst during operation. This results in a steady state performance. In addition, a fluid bed reactor is nearly isothermal by design, which minimizes catalyst deactivation due to exposure to excessive heat. The oxygen is not mixed with the hydrocarbon until both are inside the reactor. Therefore, the catalyst is present when the feeds first mix at reaction temperature and the reaction proceeds immediately. This means that the oxygen partial pressure begins to drop at once. The fluid bed process allows significantly higher levels of oxygen to be safely employed in the conversion of acetic acid and ethylene to vinyl acetate without the danger of flammability (4).

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7.2 Polymerization and Fabrication The polymerization of EVA corresponds closely to the polymerization of low density poly(ethylene) (PE). 7.2.3

Radical Solution

Polymerization

For the copolymerization of ethene and vinyl acetate, solution polymerization, suspension polymerization, emulsion polymerization and bulk polymerization may be used, but solution polymerization is preferred (1). A method of either continuous type or batch type may be employed. Methanol is generally used as the solvent. Commonly used catalysts are 2,2'-azobisisobutyronitrue, or organic peroxides. 2,2'-Azobis(4-methoxy-2,4-dimethyl valeronitrile) is the most preferred catalyst (7). The polymerization temperature is in the range of 50-80°C. The ethene pressure is 2-8 M Pa. In the case of a continuous polymerization process, the average residence time should be in the range of 3-4 h (1). To stop the polymerization reaction, a polymerization inhibitor is added to reaction mixture. Unreacted ethylene gas is evaporated and removed from the solution. Further, unreacted vinyl acetate is extracted from the copolymer solution. Eventually, methanol is recovered by precipitation with a water containing separating and purifying solution. The vinyl acetate and methanol thus recovered may be reused in the copolymerization process. 7.2.1.1 Crosslinked Polymers Polymeric binders based upon a vinyl acetate and ethylene backbone incorporating a self crosslinking monomer have been widely used in the nonwoven industry (3). Ethylene in the polymer provides softness to the product and is low cost. However, the softness in the product often comes at the expense of its wet tensile strength. Increasing the level of self crosslinkable monomer in the polymer often is not a viable option to increase the wet tensile strength. Crosslinking monomers include N-methylol acrylamide, acrylamide, further, acrylamidobutyraldehyde, dimethyl acetal, diethyl

Ethylene Vinyl Acetate Copolymers

191

acetal, acrylamidoglycolic acid, methyl acrylamidoglycolate methyl ether, or isobutylmethylol acrylamide. N-methylol acrylamide and acrylamide are commercially used crosslinkers (3). 7.2.1.2 Crosslinked Foams EVA reins can be conveniently crosslinked by both peroxide or irradiation to enhance the mechanical properties and the heat resistance. It is the crosslinking, coupled with the inherent rubbery nature of the polymer, which makes EVA suitable for production of tough and abrasion resistant foams, especially suitable for footwear applications. Crosslinked EVA foams can be manufactured by two methods (8): 1. The ionizing radiation method and 2. The chemical crosslinking method. The ionizing method is restricted to small pieces and is thus of limited use. In contrast, the chemical crosslinking method has found more commercial applicability. By crosslinking, the viscosity of EVA at high temperatures is increased and the individual cells are kept in a stable condition without rupture or agglomeration. A low density microcellular foam can be thus obtained. By selecting the vinyl acetate content, the EVA foam is flexible and highly resilient with easy coloring and adherent to other materials. The application is used widely in shoe soles, sandals and cushion materials. The foam may be manufactured by a number of methods, such as (8): • Compression molding, • Injection molding, and • Hybrids of extrusion and molding. In the first step, the acid copolymer, EVA, and crosslinking agents are mixed by heating to form a melt, along with blowing agents and other typical additives, to achieve a homogeneous compound. Mixing time, temperature, and shear rate must be regulated to ensure an optimum dispersion without premature crosslinking or foaming.

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The upper temperature limit for safe operation depends on the onset decomposition temperatures of peroxides and blowing agents employed. Preferred chemical crosslinking agents are organic peroxides, such as dicumyl peroxide (8). Preferred blowing agents are chemical blowing agents. Suitable chemical blowing agents are azodicarbonamide, dinitroso-pentamethylene-tetramine, p-toluene sulfonyl hydrazide, and p,p'-oxybis(benzenesulfonyl hydrazide). For tailoring the expansion-decomposition temperature to the foaming processes, a mixture of blowing agents is used, optionally with a blowing agent activator (8). Typical blowing agent activators are metal oxides, salts or organometallic complexes, e.g., ZnO, zinc stéarate and MgO (8). The resulting polymer foam composition is substantially of the closed cell type. This is evidenced by the fact that for equivalent densities, foams of EVA and acid copolymer are found to exhibit lower helium densities than foams of EVA alone. This is an indication that more of the cells in the EVA/acid copolymer foam are closed. Particularly for an acid copolymer content in the range of about 3-15%, the acid copolymer has been observed to be uniformly dispersed within the EVA in micron-sized particles when analyzed by transmission electron microscopy. 7.2.2

Aqueous

Emulsions

Conventionally, an EVA copolymer aqueous emulsion is produced by using a redox catalyst consisting of an oxidizing agent and a reducing agent. For example, as the reducing agent, a transition metal and formaldehyde-sodium bisulfite are often used. As the oxidizing agent to be combined with the reducing agent, sodium persulfate, hydrogen peroxide, terf-butyl hydroperoxide and the like are frequently used (9). However, when formaldehyde-sodium bisulfite, etc., are used as a reducing agent component, formalin is generated from the resultant aqueous emulsion. Formalin is assumed to be the main cause of the sick house syndrome. This is a highly undesirable phenomenon from the hygienic standpoint. However, when erysorbic acids or ascorbic acids are used as a reducing agent component instead of formaldehyde-sodium bisulf-

Ethylene Vinyl Acetate Copolymers

193

ite no formalin is produced, however, the emulsion finally obtained may be discolored. Actually, the discoloration of the resultant emulsion can be suppressed by using a specific oxidizing agent, namely, hydrogen peroxide, as the oxidizing agent (9). Surfactants having critical micelle concentration of 0.5-3%, include the dihexyl ester of sodium sulfosuccinate, sodium 2-ethylhexyl sulfate, sodium isobutyl sulfosuccinate, sodium diamyl sulfosuccinate, sodium dicyclohexyl sulfosuccinate, and sodium diisopropylnaphthalene sulfosuccinate. The dihexyl ester of sodium sulfosuccinate is a preferred surfactant (3). The polymerization proceeds in an autoclave, by dissolving vinyl acetate, poly(vinyl alcohol) (PVA), ferrous sulfate heptahydrate, and acetic acid in water. The reaction vessel is purged with nitrogen gas and heated up to 60°C at an ethene pressure of 4.6 MPa. Then, an aqueous solution of hydrogen peroxide and an aqueous solution of sodium erysorbate aqueous solution are added. The catalyst dosage is repeated at the end of the polymerization (9). Vinyl EVA copolymer emulsions can be directly produced with a content of solids of 65-75% (10). 7.2.2.1 Semicrystalline Emulsion Polymers Aqueous-based EVA polymer emulsions suited for the use in heat seal applications are produced at a comparatively low pressures process, less than 14 M Pa (2). The EVA polymer emulsions contain crystalline segments resulting from ethylene linkages. In addition to ethylene and vinyl acetate, a carboxylic comonomer is used, such as acrylamide or versa tic acid vinyl ester. The polymers have crystalline melting point of 50-90°C. A preferred way to enhance the crystalline domain formation of ethylene in the EVA polymer is to delay the addition of vinyl acetate during the polymerization process such that the unreacted vinyl acetate level present in the reactor is minimal at different stages during the process. Thus, the copolymerization can take place in the initial stage, where most of the ethylene will reside in amorphous regions, and the formation of the majority of crystalline ethylene domains can occur in the later stage of the polymerization process.

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7.2.2.2 Functionalized Emulsion Polymers Incorporation of more than 5% of a functionalized comonomer into EVA is difficult in emulsion polymerization because of several issues (11): 1. It is important to control the pH of the emulsion because functionalized monomer reactivity and emulsion stability vary with pH. 2. The polymerization of functionalized monomers in the aqueous phase can lead to high viscosity emulsions and grit formation. 3. Differences in monomer reactivity ratios often result in nonhomogeneous copolymers. 4. Levels of acrylic acid higher than 1.5% inhibit the batch copolymerization reaction of ethylene and vinyl acetate. 5. Incorporation of large amounts of functionalized monomer in the growing polymer creates a polar micellar environment that discourages migration of gaseous ethylene to the micelles. Various methods have been employed to incorporate very large amounts of functionalized monomers into EVA copolymers. Physical blends of EVA copolymers and polymers of acrylic acid have been described (12). The use of PVA stabilization systems has been described (13). 2-6% of acrylic acid (AA) can be incorporated. In order to overcome the reactivity ratio problem of AA, the use of acrylic monomers, such as n-butyl acrylate, 2-ethylhexyl acrylate, ethyl acrylate, N-methylol acrylamide, and acrylamide have been suggested (14,15). Also, the use of water insoluble comonomers based on acrylamide has been described (16). A special technique for incorporating high levels of functionalized monomers into EVA aqueous emulsion copolymers has been described in detail (11). The method consists of using the following monomers in the following amounts: 2-20% of ethylene, 20-80% of vinyl acetate, and 20-60% of a functionalized monomer, such as 2-acrylamido-2-methylpropane sulfonic acid, or

Ethylene Vinyl Acetate Copolymers

195

CH2=C(CH 3 )COO(CH 2 )nOP03H, where n is from 2 to 4. e.g., 2ethyl methacrylate phosphoric acid. 7.2.3

Saponification

When an EVA copolymer is saponified, ethylene vinyl alcohol (EVOH) units are introduced (17,18). EVOH copolymers are excellent in melt moldability, gas barrier properties, oil resistance, antistatic property and mechanical strength, and are used as various types of packages in the form of a film, a sheet, a container, etc. In these packages, visible imperfections generated at the time of molding, e.g., discoloration, fish eyes, rough surface, etc., are significant problems that need to be addressed. Thus, several improvements in the process of producing an EVOH have been proposed. In the saponification of an EVA copolymer, usually an alkali catalyst is used. The alkali catalyst acts as a catalyst for the transesterification between EVA and an alcohol. It is known that in a process where saponification proceeds mainly with this transesterification, when water is present in the reaction system, the alkali catalyst is consumed, and the reaction rate of the saponification decreases. This arises, because water accelerates the direct saponification reaction between the EVA and the alkali catalyst. Moreover, water also accelerates the reaction between an acetic acid ester formed as a byproduct in the transesterification and the alkali catalyst. Therefore, attempts to fix this problem have focused exclusively on the removal of water from the reaction system. However, this procedure results in visible imperfections in products molded from the EVOH. Actually, the appearance of an EVOH molded product can be improved by adding trace amounts of water - which is conventionally removed as a catalyst poison (17). The saponification is achieved by adding an alkali catalyst, such as sodium hydroxide, potassium hydroxide, or an alkali metal alcohólate. The saponification is carried out at 30-65°C for 1-6 h. The concentration of the copolymer solution is 10-50%, and the amount of the catalyst used is 0.02-1.0 equivalents with respect to the ester component (1). In presence of methanol, methyl acetate is formed as a by product. This can be removed by purging with nitrogen.

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O

Η2ΝΑΛ-ΝΗ2

h

Azodicarbonamide Figure 7.2: Chemical Foaming Agents

In order to get improved interlayer adhesion, the saponification degree must be 80-95 mol-%. For gas barrier applications, the saponification degree of the EVOH of 99 mol-% is required. When the saponification is insufficient, satisfactory gas barrier properties cannot be obtained (1).

7.2.4

Foaming

Foams can be produced by a foam molding process (19). In this process, the formulated molding mold is pressed and heated for a predetermined time period. During this time, gases inside the mold develop. Then, the molding die is released and rapidly opened. Thus, it is possible to form a cell structure from the gases generated during the process of decomposition of the foaming agent. The material in the molding die has still a low viscosity permitting a foaming process. Finally, the form is cooled for a predetermined time period without pressure. This step is for stabilization of the structure and shape of the individual cell in the form, and volume and physical properties of the form in consideration of the design reference size of the component or product. Azodicarbonamide, cf., Figure 7.2 is a common chemical foaming agent. It is also addressed as azobisformamide. The thermal decomposition of azodicarbonamide results in the evolution of nitrogen, carbon monoxide, and ammonia, which are trapped in the polymer as bubbles to form a foamed article.

Ethylene Vinyl Acetate Copolymers

7.3

197

Properties

7.3.1 Mechanical

Properties

The properties of EVA are close to elastomeric materials in softness and flexibility. Thus, it is competitive with rubber and vinyl products, e.g., in electrical applications. Notably, the copolymer can be processed like other thermoplastics. The material exhibits a good low-temperature toughness, and stress-crack resistance. 7.3.2 Optical

Properties

EVA shows a good resistance to UV radiation. Further, it has a good clarity.

7.4

Applications

EVA foam is used for sport applications such as • Ski boots, • Mixed martial parts, and • Waterski boots. EVA is also used in medical applications e.g., in drug delivery devices. 7.4.1

Blends

Certain aliphatic-aromatic copoly(ester)s are known to be biodegradable, i.e., they may undergo fragmentation and microbial breakdown within a composting environment. However, copoly(ester)s suffer from a poor melt strength in comparison to other resins (20). In particular, a low melt strength often results in more line breaks, instability, and lower throughput rates on processing equipment, which increases the cost of the final polymer article. This lack of processabihty has restricted the range of applications of such copoly(ester)s. Blends of aliphatic-aromatic copoly(ester)s with EVA polymers have a higher melt strength than the aliphatic-aromatic copoly(ester)

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alone and exhibit an increased melt strength and better processability. In addition, the blends show biodisintegration and biodegradability in a composting environment. Biodegradable additives include (20): • • • • •

Thermoplastic starch, Microcrystalline cellulose, Poly(lactic acid), Poly(3-hydroxybutyrate), or Poly(vinyl alcohol).

A biodégradation accelerant increases or accelerates the rate of biodégradation in the environment. For example, calcium carbonate, calcium hydroxide, calcium oxide, barium oxide, barium hydroxide, sodium silicate, calcium phosphate, magnesium oxide, may accelerate the biodégradation process. These compounds may also act as processing aids. A commonly used compound is calcium carbonate (20). The aliphatic-aromatic poly(ester)s discussed above are prepared from butanediol and a mixture of adipic acid and terephthalic acid. Blending can be performed on twin-screw extruder equipped with a medium shear mixing screw. 7.4.1.1 Biodisintegration The biodegradability can be tested using an ASTM or DIN standard (21,22). CaCOß accelerates the biodisintegration of the blends. In three experiments, identical samples each containing 5, 10, 20, and 30% CaCC>3 were compared to other samples of similar thickness containing 5, 10, 20, and 30% talc for disintegration testing in accordance with the standard (22). In all cases, the films with calcium carbonate had disintegration rates of 150% or greater than the corresponding films containing talc (20). 7.4.2 Heat Seal

Applications

It has been found that in the development of EVA polymers for heat seal applications by emulsion polymerization that the concentration of vinyl acetate and ethylene in the polymer is not solely responsible for its use as a heat seal adhesive (2).

Ethylene Vinyl Acetate Copolymers

199

Instead, the distribution of vinyl acetate and ethylene in the copolymer is a major factor. A sufficient level of amorphous ethylene vinyl acetate polymer segments is needed in order to provide adhesion to a substrate. Further, a sufficient level of crystalline ethylene polymer segments is needed to provide the proper balance of heat seal characteristics and non-blocking. Adjacent ethylene segments lead to ethylene crystallinity in the polymer. An improper amount can result in EVA polymers, which have little adhesion in terms of hot green strength and room temperature adhesive strength, but pass the non-blocking test or they may have desired adhesion but are do not meet the non-blocking test at desired temperature and pressure. In EVA polymers the glass transition temperature of the polymer can be controlled by adjusting the ethylene content. As more ethylene is present in the polymer as lower is the glass transition temperature. However, under certain conditions of polymerization the formation of crystalline poly (ethylene) domains are favored. Thus, the glass transition temperature does no longer systematically decrease proportionally to the ethylene concentration. If the ethylene moieties are short, amorphous domains are favored. Under these circumstances, the glass transition temperature decreases even more strongly. Detailed descriptions concerning the procedure of polymerization are given in the literature (2). 7.4.3

Sealing

Masonry products have been widely used in the construction industry and include building materials such as cementious materials, concrete, brick, tile, stone, grout, and like substances. Driveways, garage flooring, concrete block, brick fronts, fireplaces, fireplace hearths, as well as tiled floor, wall and counter top surfaces are exemplary applications. Masonry surfaces are porous and if left unprotected can deteriorate from exposure to water and they can become discolored. For example, water penetration can cause spalling or lead to discoloration via microbial growth. Tiles and grouts employed in homes come in contact with various foods and liquids, e.g., fruit juice, coffee, oils, ketchup, mustard, etc. that can cause discoloration.

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Motor oils, brake-oils, and transmission fluids can cause the discoloration of garage floors. Therefore, it has been common practice to coat masonry surfaces with materials capable of rendering them resistant to water, oils, and other contaminants (23). Coatings for masonry have been generally of two types, one type being a waterproof coating and another type being a water repellant coating. A coating of the waterproof type renders the surface completely impervious to both liquid water, water vapor, and other contaminants. On the other hand, a coating of the water-repellent type renders the surface impervious to water in the liquid phase but permeable to water in the gas phase. Exemplary materials for the waterproofing of masonry surfaces are waterproof membranes such as poly(vinyl chloride), PE, butyl rubber, and sealants such as tar, asphalt, paints, poly(urethane), epoxy or mastics. While these waterproofing agents can offer excellent resistance to water penetration and other contaminants, they can alter the appearance of the masonry surface, e.g., they may change the color of the surface or leave it with a shine. Waterproofing treatments can also trap moisture within the masonry surface and promote spalling. Exemplary water-repellent treatments for masonry surfaces include metal stéarates, oils, waxes, acrylates (both polymers and monomers), silicones (solvent-based and emulsion), siliconates, silanes and, fluorochemicals. In contrast, to waterproofing coatings, water-repellent coatings, because they are permeable to water vapor, do not trap moisture and, therefore they can reduce spalling. In addition most water-repellent coatings do not alter the appearance of a porous masonry. An improved process for providing water repellency and stain resistance to a masonry surface uses an aqueous based water repellant polymeric coating consisting of an aqueous emulsion of an EVA. The polymer is formed by emulsion polymerization. A portion of the ethylene is present in crystalline form. The semicrystalline ethylene portion of the polymer offers a hydrophobic, low energy film surface that resists penetration and staining by water, grease, oils, and other potential staining contaminants. Several advantages can be achieved through the process, including the ability to (23): • Impart water repellency and stain resistance to masonry sur-

Ethylene Vinyl Acetate Copolymers

201

faces, • Tolerate environmentally high temperatures without degradation, and • Employ environmentally compatible aqueous based compositions as a means of affording substantially non-discoloring water-repellent films to masonry surfaces. 7.4.4

Waxes

EVA copolymer waxes find use in a wide variety of commercial applications and are of particular interest in the manufacture of coatings or films capable of adhering to various substrates. The term wax refers generally to oligomeric polymer compounds having the following properties (24): • Solid at room temperature • Low melting point, and • Insoluble in water. In particular, EVA waxes refer generally to oligomeric polymer compounds. They are prepared by the copolymerization of ethylene monomers and vinyl acetate monomers in the same way as the high molecular weight types. Because EVA waxes tend to exhibit relatively strong adhesive properties, such waxes have been added to plastic sheathing compositions to form wire sheaths that adhere with relatively high strength to the wire cores of insulated electrical conductors (24). In addition to adhering strongly to substrates, it is often both desirable and advantageous in many applications to form coatings that are readily removable from a substrate with a minimum amount of force. In the wire sheathing industry, it is often desirable to have sheaths which can be readily removed, or stripped, to allow easy access to the conductive core for making electrical contact with the wires. Specifically EVA copolymer waxes contain about 10% vinyl acetate. The polydispersity (Mw/Mn) is around 6 and a weight-average molecular weight Mw is about 15-40 k Dalton (24).

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7.4.5 Hot Melt

Adhesives

A hot melt adhesive composition has been described that contains two types of EVA, further a hydrogenated petroleum hydrocarbon resin. This resin is obtained from a petroleum feedstock followed by hydrogénation (25). Hot melt adhesive compositions are used among others to bond edgebands. During edgebanding, the hot melt adhesive is maintained in the molten state in the glue pot of the edgebanding apparatus for extended periods of time. Fillers are added to hot melt adhesive compositions in order to decrease the costs of the adhesive composition and to improve the break action, such that it provides a clean break from the roller during the application procedure (25). 7.4.6 Cold Flow Improvers In view of decreasing world crude oil reserves and the discussion about the environmentally damaging consequences of the use of fossil and mineral fuels, there is an increasing interest in alternative energy sources based on renewable raw materials. These include in particular natural oils and fats of vegetable or animal origin (26). These oils are in general triglycérides of fatty acids with 10-24 carbon atoms. The carbon atoms and may be saturated or unsaturated. In addition, they may contain phosphoglycerides. Their calorific value is comparable to conventional fuels. However, they are considered to be less harmful to the environment. Biofuels are obtained from renewable sources and, when they are combusted, generate only as much CO2 as withdrawn form atmosphere by photosynthesis. Less carbon dioxide is formed in the course of combustion than by the equivalent amount of crude oil distillate fuel, for example diesel fuel. In addition, very little sulfur dioxide is formed. Of course, biofuels are biodegradable. Owing to the unsatisfactory physical properties of the triglycérides, the oils are converted into fatty acid esters of low alcohols such as methanol or ethanol. A drawback for the use of triglycérides and also of fatty acid esters of lower monohydric alcohols as a replacement for diesel fuel alone or in a mixture with diesel fuel has proven to be the flow

Ethylene Vinyl Acetate Copolymers

203

Table 7.2: Cold Filter Plugging Points with Certain Additives (26) Additive Comb Polymer % EVA %

a a

20 19 20 25 0

80 76 80 75 100

ppm

CFPP a [°C]

CFPP b [°C]

1500 1500 1500 1500 2500

-24 -24 -23 -23 -20

-24 -23 -21 -23 -12

Cold filter plugging points before storage Cold filter plugging points after storage

behavior at low temperatures. The reason is the high uniformity of these oils in comparison to mineral oil middle distillates. For example, rapeseed oil methyl ester has a cold filter plugging point of -14°C. The cold filter plugging point is a standardized test method (27,28). For a long time is has been impossible to obtain a cold filter plugging point value of -20°C, which is required for use as a winter diesel in central Europe. This problem is still more increased when oils based on sunflowers and soya are used. An additional problem may arise in the lacking cold temperature change stability of the formulated oils, i.e., the cold filter plugging point value of the oils attained rises gradually when the oil is stored for a prolonged period at changing temperatures in the region of the cloud-point or below. However, a method to improve the flow properties of such fuel oils of animal or vegetable origin, has been developed (26). This consists in adding a EVA copolymer or a comb polymer based on methyl acrylate and α-olefins. In addition, terpolymers of ethylene, vinyl acetate and isobutylene have been found to be useful as cold flow improvers (29). The cold filter plugging points (CFPP)s with certain additives are shown in Table 7.2. More details are given in the literature (26). A deviation between the mean values of the CFPP values after storage and the CFPP value before storage and also between the individual phases of less than 3 K shows a good cold temperature change stability.

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7.4.7 Drug Delivery EVA copolymer are used in drug delivery systems (30). Drug delivery systems based on matrices of EVA can be manufactured with extrusion technology. Based on this technology, commercially used systems have been developed. The concept of these systems comprises a coaxial fiber. In this fiber, a drug is dispersed or dissolved in a core polymer. The release of the drug from these coaxial fibers is proportional to the concentration gradient in the fiber. If the drug is present in a concentration that exceeds solubility in the membrane, on the adjacent surface the saturated concentration is established. This stationary concentration is responsible for the gradient. It has been found that the solubility of drug in the polymer is influenced by the temperature of the extrusion process (30). The extrusion temperatures of the polymer far below the melting point of the drug. Upon cooling of the extruded fibers, dissolved drugs may either recrystallize or remain soluble, which results in a supersaturated state. The amount of the dissolved drug can be correlated to the release properties. The state in which the drugs are left after extrusion determine their properties of permeation.

7.5 Suppliers and Commercial Grades Examples for commercially available EVA polymers and suppliers as well are shown in Table 7.4. Tradenames appearing in the references are shown in Table 7.3.

Ethylene Vinyl Acetate

Tradename Description

Copolymers

Table 7.3: Tradenames in References Supplier

Airflex® (Series) Air Products and Chemicals, Inc. Vinyl-ethylene emulsions (3,10) Airvol® (Series) Air Products and Chemicals, Inc. Poly(vinyl alcohol)s (10) Bruggolite® FF 6 Brueggemann Reducing agent (11) Bynel® (Series) DuPont Anhydride modified ethylene vinyl acetate resin, adhesion promoter (20) Carbowax® (Series) Union Carbide Corp. Poly(ethyleneoxide glycol) (PEG) (10) Eastar® Bio Eastman Chemical Products, Inc. Compostable Copolyester (20) Elvax® (Series) DuPont Ethylene/vinyl acetate copolymers (20) Isopar® G Exxon Isoparaffinic solvent (26) Lubrizol® 2403 Lubrizol 2-acryIamido-2-methylpropane sulfonic acid (3) Rhodacal® DS10 Rhodia Inc. Surfactant (3) Surlyn® DuPont Ionomer resin (8) Vinaco® 884 Air Products and Chemicals, Inc. Poly(vinyl acetate) (2) Vynathene® USI Chemicals EVA Copolymers (29)

205

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Engineering Thermoplastics:

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and

Styrenics

Table 7.4: Examples for Commercially Available EVA Polymers (31) Tradename

Producer

Apifive® Appeel® Brynel® Cosmothene® EVA Elvax® Escorene™ Ultra Evatane® Evathene Greenflex® Hanwha EVA Honam EVA J-REX EVA MDI EVA Nipoflex® Novatec® EVA Plexar® Samsung Total Sanren EVA Seetec EVA Toler EVA Ultrathene® Westlake EVA

API SpA DuPont Packaging & Industrial Polymers DuPont Packaging & Industrial Polymers TPC, The Polyolefin Company (Singapore) Pte. Ltd. DuPont Packaging & Industrial Polymers ExxonMobil Chemical Arkema USI Corporation Polimeri Europa Hanwha Chemical Honam Petrochemical Corporation Japan Polyolefins Co., Ltd. QPO) Modern Dispersions, Inc. Tosoh Corporation Japan Polychem Corporation LyondellBasell Industries Samsung Total Petrochemicals Co., Ltd. SINOPEC Shanghai Petrochemical Co. Ltd. Lotte Daesan Petrochemical Corp. Toler Chemical, Inc. LyondellBasell Industries Westlake Chemical Corporation

References 1. T. Kawahara and T. Tuboi, Method for producing saponified ethylenevinyl acetate copolymer, US Patent 7041 731, assigned to Kuraray Co., Ltd. (Kurashiki, JP), May 9, 2006. 2. J.J. Rabasco, C.L. Daniels, D.W. Horwat, M.S. Vratsanos, and R.H. Bott, Semi-crystalline ethylene vinyl acetate emulsion polymers for heat seal applications, US Patent 7189461, assigned to Air Products Polymers, L.P. (Allentown, PA), March 13,2007. 3. J.J. Rabasco, J.R. Boylan, D. Sagl, and R.B. Jones, Self-crosslinking vinyl acetate-ethylene polymeric binders for nonwoven webs, US Patent 7485 590, assigned to Wacker Chemical Corporation, February 3,2009. 4. L.M. Cirjak, M.F. Lemanski, D.R. Wagner, N.C. Benkalowycz, PR. Blum, M.A. Pepera, and C. Paparizos, Fluid bed process for the acetoxylation of ethylene in the production of vinyl acetate, US Patent

Ethylene Vinyl Acetate

5.

6.

7.

8.

9. 10. 11.

12. 13.

14. 15.

Copolymers

207

7166 742, assigned to The Standard Oil Company (Warrenville, IL), January 23, 2007. A. Hagemeyer, U. Dingerdissen, K. Kuhlein, A. Manz, and R. Fischer, Process for producing catalysts comprising nanosize metal particles on a porous support, in particular for the gas-phase oxidation of ethylene and acetic acid to give vinyl acetate, US Patent 6987200, assigned to Celanese Chemicals Europe GmbH (DE), January 17, 2006. A. Hagemeyer, H. Werner, U. Dingerdissen, K. Kuhlein, G. Dambeck, G. Geiss, A. Rutsch, and S. Weidlich, Catalysts for the gas-phase oxidation of ethylene and acetic acid to vinyl acetate, a process for producing them and their use, US Patent 6 849 243, assigned to Celanese Chemicals Europe GmbH (DE), February 1,2005. T. Kawahara and M. Takai, Method for manufacturing ethylene-vinyl acetate copolymer and apparatus for manufacturing the same, US Patent 6 831139, assigned to Kuraray C 3., Ltd. (Kurashiki, JP), December 14, 2004. C.-F. Hsu, R.T. Chou, WC. Whelchel, and Y.-T. Ou, Crosslinked foam of ethylene vinyl acetate copolymer and acid copolymer, US Patent 6 797 737, assigned to E. I. du Pont de Nemours and Company (Wilmington, DE), September 28, 2004. T. Sata, Method for producing ethylene-vinyl acetate copolymer aqueous emulsion, US Patent 6 635 725, assigned to Sumitomo Chemical Company, Ltd. (Osaka, JP), October 21, 2003. C D . Smith, Vinyl acetate ethylene emulsions stabilized with poly(ethylene/poly (vinyl alcohol) blend, US Patent 6673862, assigned to Air Products Polymers, L.P. (Allentown, PA), January 6,2004. D.R. Williams, Highly functionalized ethylene-vinyl acetate emulsion copolymers, US Patent 6762239, assigned to National Starch and Chemical Investment Holding Corporation (New Castle, DE), July 13, 2004. J.A. Kuphal, L.M. Robeson, and D. Sagl, Miscible blends of poly(vinyl acetate) and polymers of acrylic acid, US Patent 5171 777, assigned to Air Products and Chemicals, Inc. (Allentown, PA), December 15,1992. W.E. Lenney, High solids emulsions of vinyl acetate/ethylene copolymers containing a water soluble comonomer., EP Patent 0 389 893, assigned to Air Products and Chemicals, Inc. (Allentown, PA), October 03,1990. J.L. Walker and P.R. Mudge, Ethylene vinyl acetate polymers for latex caulks, US Patent 5120 785, assigned to National Starch and Chemical Investment Holding Corporation (Wilmington, DE), June 9,1992. T.-C. Cheng and P.A. Mango, Vinyl aceta te/ethylene/nma copolymer emulsion for nonwoven binder applications, US Patent 5109063, as-

208

16.

17. 18. 19. 20.

21.

22.

23.

24. 25.

26.

Engineering

Thermoplastics:

Polyolefins

and

Styrenics

signed to Air Products and Chemicals, Inc. (Allentown, PA), April 28, 1992. H. Okazaki and T. Ohkubo, Vinyl acetate-ethylene copolymer emulsion and aqueous emulsion adhesive composition containing the emulsion, US Patent 4446274, assigned to Denki Kagaku Kogyo Kabushiki Kaisha (Tokyo, JP), May 1,1984. N. Yanagida, Method for producing saponified ethylene-vinyl acetate copolymer, US Patent 6903159, assigned to Kuraray Co., Ltd. (Kurashiki, JP), June 7, 2005. T. Kawahara and T. Hikasa, Method for producing ethylene-vinyl acetate copolymer and saponified product thereof, US Patent 6838517, assigned to Kuraray Co., Ltd. (Kurashiki, JP), January 4, 2005. H.J. Park, Ethylene vinyl acetate based film for crosslinked blown eva foam, shoe components using the same, and method for manufacturing thereof, US Patent 7056459, June 6, 2006. M.D. Shelby, A.J. Matosky, C M . Tanner, and M.E. Donelson, Blends of aliphatic-aromatic copolyesters with ethylene-vinyl acetate copolymers, US Patent 7 241838, assigned to Eastman Chemical Company (Kingsport, TN), July 10, 2007. Standard test methods for determining aerobic biodégradation of radiolabeled plastic materials in an aqueous or compost environment, ASTM Standard ASTM D 6340-98, ASTM International, West Conshohocken, PA, 2007. Verpackung - Anforderungen an die Verwertung von Verpackungen durch Kompostierung und biologischen Abbau - Prüfschema und Bewertungskriterien für die Einstufung von Verpackungen, DIN Standard DIN EN 13432, Beuth Verlag, Berlin, 2000. Replaces DIN Standard 54900. J.J. Rabasco, G.J. Dearth, CR. Hegedus, ER. Pepe, and B.V Mukkulainen, Masonry sealing compositions comprising semi-crystalline ethylene-vinyl acetate polymer emulsions, US Patent 7459186, assigned to Wacker Chemical Corporation, December 2,2008. H.T. Hsia, Ethylene-vinyl acetate copolymer waxes, US Patent 6623855, assigned to Honeywell International Inc. (Morristown, NJ), September 23,2003. C.A. Jones and L. Chernyak, Ethylene-vinyl acetate hot melt adhesive composition and article and method incorporating the same, US Patent 6 765 054, assigned to H. B. Fuller Licensing & Financing Inc. (St. Paul, MN), July 20, 2004. M. Krull, B. Siggelkow, and M. Hess, Cold flow improvers for fuel oils of vegetable or animal origin, US Patent 7 500 996, assigned to Clariant International Ltd. (Muttenz, CH), March 10, 2009.

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Copolymers

209

27. Dieselkraftstoffe und Haushaltheizöle - Bestimmung des Temperaturgrenzwertes der Filtrierbarkeit, DIN Standard DIN EN 116, Beuth Verlag, Berlin, 1997. 28. Standard test method for cold filter plugging point of diesel and heating fuels, ASTM Standard ASTM D 6371, ASTM International, West Conshohocken, PA, 2005. 29. M.G. Botros, Ethylene vinyl acetate and isobutylene terpolymer as a cold flow improver for distillate fuel compositions, US Patent 5 681359, assigned to Quantum Chemical Corporation (Cincinnati, OH), October 28,1997. 30. J.A.H. van Laarhoven, M.A.B. Kruft, and H. Vromans, Effect of supersaturation and crystallization phenomena on the release properties of a controlled release device based on eva copolymer, /. Controlled Release, 82(2-3):309-317, August 2002. 31. IDES Integrated Design Engineering Systems, The Plastics Web®, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/prospector/, 2006.

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8 Acrylonitrile-Butadiene Styrene Polymers The history of styrenic polymers is documented by Amos (1) and Scheirs (2). The first patent of the suspension or bulk polymerization, respectively, of styrene in presence of rubbers goes back to the 1950s (3,4).

8.1

Monomers

Acrylonitrile is obtained from propylene and ammonia. 1,3-Butadiene is a petroleum hydrocarbon obtained from the C4 fraction of steam cracking. An overview on the issues of the production of butadiene is given in the literature (5). Styrene monomer is made by the dehydrogenation of ethylbenzene, which is obtained by the Friedel-Crafts reaction of ethylene and benzene. Monomers for acrylonitrile-butadiene-styrene (ABS) polymers are shown in Table 8.1 and in Figure 8.1. Table 8.1: Monomers for ABS Monomer

Remarks

Acrylonitrile 1,3-Butadiene Styrene Fumaronitrile fl-Methylstyrene Methyl methacrylate N-Phenylmaleimide

Standard Standard Standard High temperature applications High temperature applications High gloss High gloss

211

212

Engineering Thermoplastics: Polyolefins and Styrenics

1,4-Butadiene

Acrylonitrile

H3Q

O-CH3 Methyl methacrylate

/V-Phenylmaleimide

Figure 8.1: Monomers used for ABS

C-N

H-C-N - H,

^—C-N N-C-

Figure 8.2: Synthesis of Fumaronitrile (6) Fumaronitrile is produced from acrylonitrile (AN) by adding HCN followed by dehydrogenation, as shown in Figure 8.2. α-Methylstyrene is produced from cumol as an intermediate of the Hock process that is mainly used to produce phenol and acetone. α-Methylstyrene has a comparatively low ceiling temperature of only 61°C. For this reason, the homopolymerization does not proceed readily. In contrast, the homopolymer has a high glass transition temperature. Glass transition temperatures of styrene related homopolymers are shown in Table 8.2. In fact, the inclusion of α-methylstyrene as comonomer into a styrene polymer helps to achieve a higher temperature stability. In some compositions suitable for emulsion polymerized types,

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213

Table 8.2: Glass Transition Temperatures of Styrene Related Homopolymers (6, p. 324) Homopolymer from Tg/[°C] Styrene p-feri-Butylstyrene o-Methylstyrene 2,5-Dimethylstyrene 4-Phenylstyrene a-Methylstyrene

100 128 136 143 161 168

styrene and AN have been wholly or partially replaced by a-methylstyrene, methyl methacrylate, or N-phenylmaleimide (7). This results in compositions with a high degree of toughness, very good processability and extremely high gloss. 8.1.1

Rubbers

Typical rubbers are ungrafted low gel diene rubbers, or mixtures of diene rubbers. Such rubbers include copolymers and block copolymers of conjugated 1,3-dienes, substituted styrene monomers and other monomers as shown in Table 8.3. A useful group of rubbers are the stereo specific poly(butadiene) rubbers formed by the polymerization of 1,3-butadiene. These rubbers have a cis-isomer content of more than 30%. They contain at least about 85% of poly(butadiene) formed by 1,4 addition. Further, the rubber should have a second order transition temperature of preferably not higher than -20°C (8). The rubber content of the ABS polymer, is expressed in terms of the weight of the original rubber feed, rather than of the grafted rubber produced during polymerization. This is not necessarily the same as that charged to the reaction mixture. This arises, because the rubber is necessarily in the polymeric part of the reaction mixture such that removal of unreacted monomer after polymerization has reached the desired level, will result in a correspondingly higher proportion of rubber in what remains. The conversion of monomers to polymer can be run from 30 to 99%. For example, if monomer separation is carried out after only 50% conversion of the monomers, then the rubber content would

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Table 8.3: M o n o m e r s for Rubbers (8) Bifunctional Compounds 1,3-Butadiene Isoprene 2-Chloro-l ,3-butadiene l-Chloro-l,3-butadiene Piperylene Monofunctional Compounds Styrène Methylstyrene o-Methylstyrene m-Methylstyrene 4-Methylstyrene o-Ethylstyrene m-Ethylstyrene p-Ethylstyrene 2,4-Diinethylstyrene a-Methylstyrene o-Chlorostyrene Acrylonitrile Methacrylonitrile Acrylic acid Ethyl acrylate Butyl acrylate 2-Ethylhexyl acrylate Methacrylic acid

Styrenics

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215

be increased by about 100% over that which would be obtained if the polymerization were allowed to proceed up to 100% conversion was reached. Hence, the rubber content of the ABS polymer can be controlled readily by the amount fed and the conversion level of the monomers before separating the residual monomers. Analysis of the processes of polymerization revealed that the production volume of the ABS resin increases by shortening the processing time with a shorter reaction time, an increase in the rubber content of latex, a decrease in the rubber content of the final ABS injection molding products and extrusion products, or an increase in the total solid content of latex (9). Methods that enable the preparation of rubbers with a high solid content have been described (9). A reactive emulsifier is used in this process. The reactive emulsifier is a poly(oxyethylene) allyl glycidic nonylphenyl ether sulfate. The latex is prepared otherwise in a conventional way. The reactive emulsifier, is used in order to decrease in the amount of coagulated materials which are generated during the emulsion copolymerization, and to prevent the film from being formed on the latex surface. Thus, the ABS rubber latex has a high productivity· and a high total solid content.

8.2

Polymerization and Fabrication

8.2.1 Mass

Polymerization

In a typical ABS mass polymerization process, styrene and acrylonitrile are copolymerized in the presence of a diene-based rubber. Initially, the rubber is dissolved in the monomers and a continuous homogeneous phase prevails. The polymerization may be initiated by any free radical generating initiator that promotes grafting and is activated at the contemplated reaction temperatures. Suitable initiators are summarized in Table 8.4. When the polymerization begins, the monomers are simultaneously copolymerized alone and also as a graft on the rubber backbone. As the monomers polymerize, two phases appear (8): 1. The polymer dissolved in monomer and 2. The rubber dissolved in monomer.

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Engineering Thermoplastics: Polyolefins and Styrenics Table 8.4: Radical Initiators for Mass Polymerization Peroxides

References

ferf-Butyl perbenzoate ferf-Butyl peroxy isopropyl carbonate ferf-Butyl peroctoate ferf-Butyl peroxy isononoate ferf-Butyl 2-ethylhexyl monoperoxy carbonate ferf-Butyl peroxyneodecanoate 1,1-Di-ferf-butylperoxycyclohexane

(8) (8) (8) (8) (8,10) (10,11 ) (12)

Initially, the second phase predominates and the smaller polymer in monomer phase is dispersed in the larger rubber in monomer phase. However, as polymerization proceeds, the polymer in monomer phase becomes greater in volume. At this point, the phenomenon of phase inversion occurs and the rubber in monomer phase becomes dispersed as discrete particles in a matrix of the polymer in monomer phase. Usually in a mass polymerization process, the rubber will contain occlusions of polymer/monomer, which serve to swell the volume of the rubber particle. In the course of polymerization, monomer is converted to polymer, the viscosity of the mixture increases and greater power is needed to maintain the temperature and the compositional uniformity throughout the polymerized material (8). 8.2.1.1 Polymers With High Content of Acrylonitrile Originally, processes were common that involve the feeding of a solution of rubber in a mixture of styrene and acrylonitrile monomers to the polymerization mixture. These processes have the inherent limitation in that they cannot produce polymers with a high rubber content. This occurs because in spite the rubber dissolves readily in styrene. However, its solubility in a mixture of styrene and acrylonitrile monomers decreases with the concentration of acrylonitrile. For example, styrene monomer can dissolve about 20% of its weight of a diene rubber, whereas a monomer mixture containing 58% styrene and 42% acrylonitrile can dissolve less than 10% of its weight of the same rubber. For this reason, the amount of rubber that can be added in so-

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217

lution in the monomer mixture is restricted by the proportion of nitrile monomer. However, for many purposes, such as solvent resistance and toughness, it is advantageous to have a proportion of acrylonitrile as high as 40% or more by weight. A process has been developed by which ABS polymers with high proportions of both rubber and acrylonitrile may be obtained. This represents a significant advance in the art (8). In this particular process, the rubber is dissolved in styrene monomer in amounts of 10-30%. This solution is charged to the reactor, which provides a continuous polymerization zone containing a polymerizing mixture with a substantially uniform composition throughout. The reactor operates at a steady state with a polymer solids level above that at which phase inversion occurs and up to 70% polymer solids. Operation at such a polymer solids content ensures that upon addition the rubber immediately forms small particles containing a monomer component, dispersed in the partially polymerized reaction mixture. Because acrylonitrile is separately but simultaneously fed and because the point of phase inversion for the system has been passed such that the rubber disperses as particles as it enters the reaction mixture, the process has the capability of employing high rubber concentrations while still realizing a high acrylonitrile concentration in the final ABS composition (8). 8.2.1.2

Continuous Mass Polymerization

A continuous mass polymerization process for making an extrusion grade ABS resin has been described (11 ). It would be straightforward to start with a certain feed that runs as such through the reactor cascade. However, it is more advantageous to add between first and second reactor some monomer feed including certain additives. The continuous polymerization is conducted in a cascade of reactors. A typical feed is given in Table 8.5. Suitable inert solvents include methyl ethyl ketone, benzene, ethylbenzene and toluene. Suitable initiators include peresters and peroxycarbonates such as ferf-butyl perbenzoate, íerí-butyl peroxy isopropyl carbonate, fírf-butyl peroctoate, tert-buty\ peroxy isonon-

218

Engineering Thermoplastics: Polyolefins and Styrenics Table 8.5: Feed for Continuous Polymerization (11) Feed into first reactor, 80°C, 0.5 kg h" ' Poly(butadiene) rubber Styrene Acrylonitrile Inert solvent ferf-Butyl peroxyneodecanoate Feed into second reactor, 150°C, 0.03 kg h"1 Product from first reactor Styrene Acrylonitrile Corn oil Stabilizer

% 8.1 48.6 20.1 23.2 0.023 % 68.2 13.5 12.2 6.1

oate, ferf-butyl 2-ethylhexyl monoperoxy carbonate, ferf-butyl peroxyneodecanoate, and mixtures of these compounds. The initiator is included in an amount of 0.02-0.05%. No initiator is added to any subsequent reactor in the process. It is often desirable to incorporate chain transfer agents, e.g., dodecylmercaptan in amounts of 0.01-1.0%. In addition, it may be advantageous to include small amounts of antioxidants or stabilizers, such as alkylated phenols. 8.2.2 Emulsion

Polymerization

ABS products with high impact strengths and relatively high surface gloss may be produced by using traditional emulsion polymerization techniques. ABS compositions with bimodal particle size distributions of the grafted rubber can be prepared by emulsion graft polymerization techniques. The preparation of ABS types by emulsion polymerization consists in brief of (13): 1. Preparation of an aqueous elastomeric polymer emulsion of colloidally dispersed small particles with a particle size of 0.15-0.22 μ, 2. Agglomeration of the particles in the emulsion, 3. Graft polymerization, as emulsion polymerization,

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4. Separating the resulting emulsion, and 5. Melt compounding. Conventional anionic emulsifiers are alkyl sulfates, alkyl sulfonates, aralkyl sulfonates, soaps of saturated or unsaturated fatty acids and alkaline disproportionated or hydrogenated abietic or tall oil acids (14). In the agglomeration step, the latexes are partially agglomerated using a core/shell agglomerating agent latex, which consists of an elastomeric 1,3-butadiene/slyrene copolymer core and an ethyl acrylate/methacrylic acid copolymer shell. This partial agglomeration operation should not be confused with a coagulation operation where the emulsion is fully destabilized (13). The partial agglomeration technique has been described in detail elsewhere (15). The colloidal stability of the dispersed polymer particles is not destroyed in the partial agglomeration process. The agglomeration step involves treatment of the dispersed rubber particles at a stage where they have no outer protective layer of non-rubbery, i.e., rigid polymer to prevent the massive or complete coalescence of the rubber particles (13). The graft polymerization of the resulting partially agglomerated aqueous elastomeric polymer emulsion is performed according to known emulsion graft polymerization techniques. The desired monomer mixture is added to the rubbery polymer emulsion along with initiators, chain transfer agents, etc. For example, as monomers a mixture of styrene and acrylonitrile in the weight ratio of 77:23 has been used (13). A common chain transfer agent is dodecylmercaptan (14). Further, dimeric α-methylstyrene and terpinolene have been claimed to be useful transfer agents (16). Initiators for emulsion polymerization are shown in Table 8.6. Eventually, the latexes are dewatered and recovered in solid form by freeze-coagulation and centrifugation, or by mechanical isolation. Mechanical isolation consists of shear coagulation of the latex to form a paste. The paste is then heated and sheared to form a crumb. Finally, the crumb is mechanically dewatered and ground to the desired particle size. A key feature of this method is the relatively low energy consumption of this process (17).

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Table 8.6: Initiators for Emulsion Polymerization Organic Peroxides Di-ferf-butyl peroxide Cumene hydroperoxide Dicyclohexyl percarbonate Diisopropylbenzene hydroperoxide ferf-Butyl hydroperoxide p-Menthane hydroperoxide

References (14) (14,18) (14) (18) (14) (14)

Inorganic Peroxides Ammonium persulfate Sodium persulfate Potassium persulfate Potassium perphosphate Sodium perborate Hydrogen peroxide

(14,18) (14,18) (14,18) (14) (14) (14)

Azo initiators 2,2'-Azobisisobutyronitrile 4,4'-Azobis(4-cyanovaleric acid) 2,2'-Azobis(2-methylbutyronitrile)

(14,16) (18) (16)

Acrylonitrile-Butadiene-Styrene 8.2.3

Polymers

221

Low Gloss Types

Low gloss types are fabricated from bulk polymerization, since low gloss can be effected by a larger particle size of the polymer. 8.2.4 8.2.4.1

Blends Blends by Mixing

Compositions of the ABS type may be mixed with other polymers. Suitable blend partners can be selected from poly(carbonate)s (PC)s, poly(ester)s, poly(ester carbonate)s and poly(amide)s (PA)s. Some especially preferred types of these compounds and an overview of how to produced these types have been described (16). Actually, ABS can be considered as an impact modifier for PC. PC/ABS blends have been compatibilized with both maleic anhydride (MA)-grafted poly(propylene) (PP) and a solid epoxy resin of the bisphenol A type. Both compatibilizers are effective for formulations of an ABS content up to 30%. The the impact strength of the compatibilized blends was close to that of PC. However, above 40% ABS content, the impact strength decreases significantly (19). Polymer mixtures of aromatic PC, ABS graft polymer and styrene-containing copolymers and monophosphates are described as flameproofing additives (20). It has been claimed that phosphonate amines are superior flame retardants for PC/ABS molding compositions (21). To improve the long-term service life of PC/ABS composites, in particular when used at elevated temperature and ambient humidity, it is desirable to improve the hydrolysis resistance of these materials (22). The addition of very finely divided calcium carbonates with an average particle diameter of less than 100 nm greatly increases hydrolysis resistance without impairing the toughness of the blend. Antistatic Compositions. Antistatic properties can be imparted to ABS polymers by coating the surface of the resin with surfactants or by incorporating surfactants into the resin by kneading. Further, it has been proposed to admix an epihalohydrin polymer or an ethylene oxide copolymer.

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Engineering Thermoplastics: Polyolefins and Styrenics

However, it has been stated that articles fabricated from such resins become impaired with regard to their performance (23). Compositions of ABS polymers that contain a special ethylene oxide copolymer have been developed, which do not suffer from these drawbacks. The ethylene oxide copolymer consists of ethylene oxide and 1-naphthyl glycidyl ether. The copolymer a should have a high refractive index of more than 1.50. The presence of this copolymer in the ABS resin composition gives a product of remarkably improved surface appearance when the composition is subjected to injection molding. In addition, the resin composition has an excellent antistatic property (23). Poly(amide) Blends. PA resins exhibit good chemical resistance, mechanical strength, heat resistance, and abrasion resistance and is widely used for electric-electronic parts, machine parts and automobile parts. However, this resin is disadvantageously poor in its impact strength. On the other hand, high impact poly(styrene) (HIPS), ABS, acrylonitrile-ethylene-propylene-based rubber/styrene copolymer resin (AES), acrylonitrile/acryl-based rubber/styrene copolymer resin (AAS) show excellent impact strengths, but these resins are inferior in chemical resistance and abrasion resistance. In order to mutually redeem these disadvantages of respective resins, a blend of a PA resin and an ABS resin has been proposed. However, the compatibility between PA and ABS resin is poor. Therefore, a technique of copolymerizing an unsaturated carboxylic acid with styrene or acrylonitrile and blending the obtained unsaturated carboxylic acid-modified copolymer as a compatibilizer has been proposed. In these formulations, an improvement in the compatibility, and the impact strength is obtained. In addition, modern fabrication techniques demand good molding characteristic, i.e., low melt viscosity, in order to enhance the shaping cycle and increase the productivity. When a layered silicate, e.g., montmorillonite is added as an inorganic filler, the fluidity and the surface properties can be improved (24). Conductive Poly(amide) Compositions. Composites of PA-6 and carbon nanotubes (CNT)s show a significant increase of about 27%

Acrylonitrile-Butadiene-Styrene

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223

in the Young's modulus, however the elongation at break of these materials dramatically decreases due to an embrittlement caused by PA-6. Therefore, blends of these composites and in addition with ABS have been prepared by extrusion (25). Transmission electron microscopy measurements reveal that the nanotubes are selectively located in the PA-6 phase. The selectively filled PA-6/ABS blends show a highly irregular, cocontinuous morphology. Because the conductive filler is located into a single component of the blend, these materials show an onset in the electrical conductivity at very low filler loadings of 2-3%. These findings have been explained by a double percolation effect. The CNT filled blends show superior mechanical properties in the tensile tests and in impact tests (25). Poly(Mactide) Blends. In recent years, poly(/-lactide) (PLLA) received increasing attention because it is produced from renewable recourses and because of its biodegradability. PLLA has been widely used in biomédical applications. Further, it is believed to be an alternative to traditional commodity plastics for everyday applications since it is an environmental friendly polymer. However, its toughness and heat distortion temperature are not very satisfactory for these applications. This drawback can be at least partially eliminated by blending PLLA with other polymers (26-29). In addition, ABS has been used for blending (30). The blends were prepared laboratory mill equipped with a twin-screw. It turned out that uncompatibilized blends of PLLA and ABS have a morphology with big phase size and a weak interface. The blends exhibit poor mechanical properties with low elongation at break and decreased impact strength. However, a reactive styrene acrylonitrile copolymer (SAN)/glycidl methacrylate copolymer was found to be an effective reactive compatibilizer for the blends. Ethyltriphenyl phosphonium bromide was used as the catalyst. Probably, the epoxide groups react either with carboxyl or with hydroxyl groups of the PLLA end groups. This so modified polymer acts as the compatibilizer. Compatibilized PLLA/ABS blends exhibit an improved impact strength and an im-

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Engineering Thermoplastics: Polyolefins and Styrenics

proved elongation at break with only a slight loss in the modulus and tensile strength (30). Poly(trimethylene terephthalate). Poly(trimethylene terephthalate) (PTT) is a crystalline polymer that is used for fibers, films, and engineering plastics. The polymer has an outstanding tensile elastic recovery, good chemical resistance, a relative low melting temperature, and a rapid crystallization rate. It combines some of the advantages of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT). Disadvantageous are the low heat distortion temperature, low melt viscosity, poor optical properties, and pronounced brittleness low temperatures. ABS is a feasible choice for blending with PTT, because of their potential combination of good impact strength, modulus, heat and chemical resistance, and abrasion resistance (31). In blends of PTT and ABS, two separate glass transition temperatures are observed, which indicates that the blends are phase separated in the amorphous phase. A styrene/butadiene/maleic anhydride copolymer or glycidyl endcapped epoxy resin may act as a compatibilizer. Compatibilized PTT/ABS blends show a finer morphology and better adhesion between the phases. 8.2.4.2

Blends by Reaction

Poly(carbonate) Compositions. Thermoplastic blends are usually produced by mixing and homogenizing the components in the melt. However, some thermoplastic blends have hitherto not been accessible by this route, since the difference in processing temperatures is too great, and a joint compounding operation is only possible if it is accepted that one or more of the blend components will undergo degradation. In such a mode of operation, the overall property profile of the resulting blend may be adversely affected by the thermal degradation of one blend component. In this case, blends of PC and ABS graft polymers can be produced by mixing oligocarbonates and ABS in the melt. There the oligocarbonates are condensed under reduced pressure to form a high molecular weight PC. Particularly, an oligocarbonate is prepared from bisphenol A and

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225

diphenyl carbonate with sodium phenolate. Then, the oligomers are further condensed in the presence of ABS at temperatures from 270°C at 0.7 mb in a vacuum evaporator (32). Tough Compositions. The toughness of a thermoplastic, rigid poly(urethane) (PU) can be markedly improved by incorporating ABS resin. The ABS resin is mass-polymerized. The PU compositions can be prepared by dispersing the mass ABS resin in the reactants used to prepare the PU and then contacting the resultant dispersion with the other urethane reactants under conditions sufficient to form the PU. The reaction can be accelerated by the addition of suitable urethane catalysts, for example by tertiary amines (33). When the PU is prepared by reactive extrusion, the ABS resin may be added already initially along with the urethane-forming reactants. This toughened PU is particularly useful in making structural automotive body parts and housings for electrical appliances. In the same way, ABS acts as a toughener for vinyl ester resins (34). Assessment of the mechanical properties suggest that a chemical reaction may have occurred between the constituents of the blends. The blends are intended as a toughening agent for interlayer toughened vinyl ester/glass composite materials. 8.2.4.3

Functionalized Acrylonitrile-butadiene-styrene Polymers

Blending of immiscible polymers opens attractive opportunities for developing new materials with useful combinations of properties. The topic has been extensively reviewed (35-37). Simple blends often exhibit poor mechanical properties and unstable morphologies. A solution consists in the compatibilization of such blends. Graft or block copolymers are added to the blends in order to act as compatibilizers. However, often it is difficult to produce suitable graft or block copolymers for important commercial applications. Alternatively, these compatibilizing copolymers can be generated in situ during the blend preparation through polymer-polymer grafting reactions using functionalized polymers (38).

226

Engineering Thermoplastics: Polyolefins and Styrenics Table 8.7: Vinyl Monomers Grafted on ABS Grafted Monomer References Maleic anhydride Acrylamide Acrylic acid Methacrylic acid Crotonic acid Undecylenic acid

(39-42) (43) (44) (24) (45) (46)

Grafted Polymers. Due to the special chain structure ABS terpolymers have been widely modified by grafting vinyl monomers onto the main chain. We emphasize that the method how ABS itself is obtained is addressed sometimes as grafting styrene and acrylonitrile onto a butadiene rubber. Here we focus on grafting reactions on the ABS itself. Some examples of ABS grafted polymers are shown in Table 8.7. The pending acid functionalities may be allowed to react with amines and other compounds (45). Graft polymers can be obtained by reactive extrusion (47). Likewise, the grafting can be performed in solution. In the solvothermal method, the polymer is dissolved in a solvent and the solution is in a vessel. The material can be heated even above the critical point of the solvent (42). In the past, this method was mostly used in inorganic chemistry, however using this method MA could be successfully grafted onto ABS. As initiators, common peroxides, such as dicumyl peroxide, dibenzoylperoxide can be used, but also photo initiators have been reported. Photoinitiating systems are the combinations of benzophenone with amines, such as n-butylamine, trimethylamine and triethylamine (43). Another way of photoinitiation is the anthracene photosensitized formation of hydroperoxides in the butadiene portion of the polymer (44). Vinyl monomers react preferably with the pendent double bonds of ABS (39). In grafting undecylenic acid, a monomer cage effect has been observed. The kinetic law follows a 1.5th power of the monomer concentration (46). The overall initial rate of polymerization Rp can be described as

Acrylonitrile-Butadiene-Styrene

R

_.A

Rp A

[P}[h][M]"

- ([p)+B[M]»r

Polymers

227

(81)

Here, M, P, and h denote the monomer, polymer, and initiator, respectively. Compatibilizer Polymers. ABS copolymers that are functionalized may act as a compatibilizer for other polymer blends. These types are grafted in the same way as polymers dealt with above. Compatibilizer ABS copolymers have been prepared via an emulsion polymerization process. These copolymers have been functionalized with glycidyl methacrylate (GMA). The functionalized copolymers are blended PBT. Characterization by thermal mechanical analysis indicates that PBT is partially miscible with ABS and the glycidyl grafted ABS (48). Scanning electron microscope measurements show a good dispersion of the grafted particles in the PBT matrix even at low amounts of admixture. However, a coarse, phase morphology is obtained when the disperse phase contains a high content of GMA of around 8%. This seems to happen due to crosslinking reactions between the PBT and the glycidyl groups. Rheological measurements confirm the reactions between PBT and GMA.

8.3

Properties

Since ABS is composed of a hard material and a soft material, it combines the rigidity of acrylonitrile and styrene polymers with the toughness of butadiene rubbers. Most advantageous is its impact resistance and toughness. ABS can be tailored to improve the impact resistance, toughness, and heat resistance. Selected properties of an ABS type are shown in Table 8.8. 8.3.1 Mechanical 8.3.1.1

Properties

Carbon nanotubes

ABS can be reinforced with CNTs. ABS reinforced with CNTs has been investigated. As expected, it exhibits an improved strength

228

Engineering Thermoplastics: Polyolefins and Styrenics Table 8.8: Properties of an ABS Polymer a (49) Property Density Mold Shrink, flow 0.0035 to Water absorption (saturation 23°C) Tensile Modulus Tensile Strength, yield, 23°C Tensile Elongation, yield 23°C Flexural Modulus, 23°C Notched Izod Impact, 23°C CLTE, Flow (TMA) Volume Resistivity a

Value

Unit

1.04 g/cm 3 0.55 % 1 % 2300 MPa 45 MPa 2.6 % 2300 MPa 300 J/m 9.5E-5 cm/cm/°C 1.0Ε+13Ωαη

Terluran® GP-22, BASF

and higher tensile elastic modulus (50). Another study that focussed on the glass transition temperature of such composites revealed that the a-relaxation in the acrylonitrile/ styrene phase is broadened towards higher glass transition temperatures. It is believed that the shift arises due to the interaction located at the boundary layer between polymer and CNTs (51). 8.3.2

Thermal Properties

The release of semivolatile compounds from a variety of nitrogen containing polymers, including ABS, PA 6 PU and melamine/urea formaldehyde resins can be found in the literature (52). The temperature of treatment runs from 70°C to 300°C, i.e., low temperature pyrolysis, if pyrolysis at all. The thermal degradation of the plastics has been performed using a horizontal quartz reactor of 200 mm length and 20 mm inner diameter. Synthetic air was used as a purge gas at a constant flow rate of 200 ml min" 1 . The semivolatile compounds emitted were collected in a series of three gas samplers containing no solvent, dichloromethane and hexane. The substances were analyzed and characterized by gas chromatography (GC)/mass spectroscopy (MS). Extensive compilations of the nature of the analyzed products are available (52). ABS generates the highest numbers of semivolatile compounds during thermal degradation among the plastics examined.

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Potential hazards in the case of fire can be expressed as the specific heat release on combustion. ABS has a specific heat release of about 35 kjg" 1 . In comparison, PC has a specific heat release of about 17 kjg" 1 (53). ABS decomposes almost without charring. Thus, in case of fire, most of the material is transferred into the gas phase. For these reasons, the addition of ABS to PC in order to form blends increases the fire hazard and thus the demand of adding flame retardants. The flame retardant mechanism of PC/ABS compositions using bisphenol A bis(diphenyl phosphate) (BDP) and zinc borate have been investigated (54). BDP affects the decomposition of PC/ABS and acts as a flame retardant in both the gas and the condensed phase. The pyrolysis was studied by thermogravimetry coupled with fourier transform infrared spectroscopy (FTIR) and nuclear magnetic-resonance spectroscopy. Zinc borate effects an additional hydrolysis of the PC and contributes to a borate network on the residue. A comparative study of the efficiency of some commercial aryl phosphates for PC/ABS composites revealed that BDP is superior in comparison to triphenyl phosphate (55). 8.3.3 Electrical Properties Traditionally, ABS is used as an insulator because of its high electrical resistance. However, if electrically conducting additives, such as carbon black are added to the ABS resin, the number of potential applications for this material can be markedly increased. Examples of conductive ABS polymer composites include electromagnetic shielding materials (56,57) and electrically conductive composite plastic sheets, which may be used for packaging of integrated circuit devices (58,59). For the packaging of electronic components, antistatic features are usually required. This arises because circuits may be damaged by static electrical charges if they are packed in insulating sheets. Besides rendering the conductivity of ABS, carbon black also works as a pigment and can also help reduce photo-oxidation (60). ABS/Carbon black composites have been fabricated in a twinscrew extruder. It became obvious that once-extruded compos-

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ites had a porous structure and a poor conductivity. In contract, twice-extruded composites were much more homogeneous and had a higher electrical conductivity. The percolation threshold of the twice-extruded composites was at 8-10% of carbon black loading (61). 8.3.4 Optical Properties 8.3.4.1

UV Stability

In order to investigate the UV Stability of ABS, specimens were exposed in a weatherometer. The ambient temperature of 30°C ensured that the mechanism of UV degradation was not interfered by thermal effects The specimens were exposed under accelerated conditions for 3 months, with periodic assessments of their performance (62). The measurement of the chemiluminescence reveals that the degradation reaction is limited surface of the materials. A comparatively rapid consumption of the stabilizer is observed, relative to the bulk region of the specimen. FTIR measurements indicate that the surface-specific UV degradation results in the formation of products in that the vinyl unsaturation is lost. Thus, it is believed that the irradiation causes a crosslinking of the material. This is in accordance as the material becomes brittle on irradiation. It has been proposed that surface degradation after UV exposure promotes brittleness and may therefore influence the failure mechanism. This is of particular importance for ABS pressure pipes that are continuously under static loading. A methodology for estimating the lifetime of UV exposed ABS pipes has been proposed (62). 8.3.4.2 Laser Beam Weldability The laser beam weldability ABS plates has been investigated both from an experimental and theoretical approach (63). ABS is a complex mixture consisting of several ingredients as discussed above. The presence of the rubber occlusions renders ABS inhomogeneous from the optical point of view.

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In modelling the welding process, an optical model has been used to determine how the laser beam is attenuated in the course of passage. This information has been used as the basic input to a thermal model. From there, the evolution of the temperature field in the material could be estimated. Comparing the results from the model with the experimental results, some insight about the fundamental phenomena that govern the process could be obtained. It has been concluded that the approach chosen in the study should be an efficient tool in determining the weldability of polymers in general (63). It is believed that the consequent application of the proposed method should result in a significant reduction of time and costs when exploring the weldability of hitherto unknown systems. 8.3.5

Surface Properties

Plasma treatment is useful to activate the surface of a certain material. The treatment enhances the adhesion property. Basically, surface activation effects the introduction of chemical functionalities on the polymer surface in order to increase its surface energy. The wettability of ABS can be increased by the treatment with an atmospheric plasma torch (64).. This was established by contact angle measurements and other methods. The wettability was increased when the atmospheric plasma treatment was done in a slow manner. The decrease in contact angle with respect to water is explained due to a significant increase in the oxygen content, which is caused by the formation of carboxylic and hydroxyl groups on the polymer surface. After natural ageing, again an increase in the water contact angle, was observed. However, the values of the untreated polymer surface were never reached.

8.4

Special Additives

Several additives are common in producing moldable ABS resins. These include lubricants, mold release agents, antistatic agents, heat stabilizers, light stabilizers and flame retardants (65).

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Engineering Thermoplastics: Polyolefins and Styrenics Table 8.9: Flame Retardants for ABS Blends References

Compound Triphenyl phosphate Tricresyl phosphate Diphenyl-2-ethyl cresyl phosphate Triisopropylphenyl phosphate Tris-(2-chloroethyl)phosphate Methylphosphonic acid diphenyl ester Phenyl phosphonic acid diethyl ester Diphenyl cresyl phosphate Bisphenol A bis(diphenyl phosphate Tributyl phosphate m-Phenylene-bis(diphenyl phosphate) 0,ODiphenyl-N-phenylphosphoramidate l,3-Phenylene-N,Ñ'-bis(0,0-diphenylphosphoramidate) Piperazinediyl-N,N'-bis(0,0-diphenylphosphoramidate 5,5,5',5',5",5"-Hexamethyl tris(l,3,2-dioxaphosphorinane-methane)amino-2,2',2"-trioxide Pentaerythritol bis(phenyl phosphate) Tris(2,4-di-ferf-butylphenyl)phosphite Ammonium polyphosphate Decabromodiphenyl oxide l,2-Bis(tribromophenoxy)ethane

8.4.1 Heat

(20,21,66) (20,21) (20,21) (20) (21) (20) (20) (20) (54) (20,21) (67) (68) (68) (68) (22) (69) (70) (70) (71) (72)

Stabilizers

Heat stabilizers can be selected from benzothiazoles, benzimidazoles hydrazine compounds, and cation exchange materials (73). Moreover, the addition of heat stabilizers results in an improvement of the impact resistance.

8.4.2 Flame

Retardants

A series of flame retardant additives for ABS have been discussed, including halogen containing flame retardants, as well as halogen free flame retardants. The latter are being preferred for environmental reasons, however, only a few are as effective as halogen containing flame retardants. For ABS blends, some flame retardants (20) have been described that are summarized in Table 8.9.

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Figure 8.3: Synthesis of Amino phospohonates ABS/clay nanocomposites that are prepared by a direct melt intercalation technique without any conventional flame retardant, show an enhanced formation of char in the course of thermal degradation and thus exhibit an improved thermal stability (74). Other, preferable compounds are from the class of amino phospohonates (21). The preparation of several phosphoramidate compounds has been described in detail (68). The basic route of synthesis is shown in Figure 8.3. Certain órgano cyclic phosphorus compounds have been proved to be particularly efficient for ABS. Some spiro phosphorus compounds are shown in Figure 8.4. The effectiveness is particularly dependent on the content of phosphor. Whereas pentaerythritol diphenyl diphosphate burns even at a loading of 35%, pentaerythritol bis(phenyl phosphate) reaches a V-0 rating at this loading, pentaerythritol bis(methyl phosphate) needs only a loading of 15% to reach a V-0 rating (69). When triphenyl phosphate is intercalated into mica nanoparticles, the evaporation temperature triphenyl phosphate increases. By adding this nanocomposite to ABS, the thermal stability is enhanced. When in addition an epoxy resin and a silane coupling agent is added, for example, ß-(3,4-epoxy cyclohexyl) ethyl trimethoxysilane, a large increase in the limiting oxygen index (LOI) is observed (75). A maximum LOI value of 44.8 for such formulations has been reported, in comparison to 18.2 for pure ABS. Thus, epoxy compounds can be addressed as very efficient synergistic flame retardants for ABS compositions (76). Ammonium polyphosphate is the most important inorganic ni-

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Engineering Thermoplastics: Polyolefins and Styrenics

v

.xxx, ê °%

Pentaerythritol bis(methyl phosphate)

Pentaerythritol bis(phenyl phosphate)

Pentaerythritol diphenyl diphosphate Figure 8.4: Spiro Phosphorus Compounds (69) trogen-phosphorous compound that is an intumescent flame retardant. A detailed study on the nature of the products of pyrolysis form ABS in the presence of ammonium polyphosphate or tris(2,4-di-£er£-butylphenyl)phosphite as flame retardants has been performed. Detailed tables on the nature are given in the original paper (70). Significant changes in the distribution of the products of pyrolysis were observed with the flame retardants mentioned above. This indicates that the polyphosphoric residue of ammonium polyphosphate modifies the mechanisms of the thermal decomposition of these polymers. The use of silicones to render PC/ABS blends flame retardant, at least by any economically viable means, is not possible (77). However, by the phosphonation of silanes, flame retardants can be synthesized. The reaction is shown in Figure 8.5. The products of the first step can further undergo oligomerization. 8.4.3

Combined UV Stabilizer and Flame Retardant

Benzoylresorcinol has been used in the plastic and polymer industries to protect plastic and polymer materials against the harmful

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Figure 8.5: Synthesis of Phosphonated Silanes from Dimethyl methane phosphonate and Diphenyldichlorosilane (77) effects of the UV radiation from the sun. However, the use of benzoylresorcinol in flame retardants and their applications in plastics were not realized before. The use of benzoylresorcinol in the synthesis of phosphate ester type flame retardants may improve their UV resistance, their thermal stability, and possibly their hydrolytic stability, in addition to the flame retardant properties. Benzoylresorcinol based phosphate esters are obtained by reacting a benzoylresorcinol compound with a chlorophosphate, e.g., benzoylresorcinol with diphenyl chlorophosphate or phosphorus oxychloride. These esters can function both as flame retardants and UV stabilizers for PC/ABS and a series of other polymers (78). Flame retardants are often used in combination with anti-drip agents, which reduce the tendency of the material to form burning droplets in the event of fire (67). Fluorinated polyolefins are preferably used as anti-drip agents (22,67). 8.4.4

Fillers

In an ABS/metal composite, 10% iron powder has been admixed. The main reasons for choosing iron powder as short fiber fillers were its reasonably good mechanical and thermal properties as well as its capabilities of mixing and surface bonding with polymers (79). The shape of the iron particles was spherical. The composite was used for fused deposition modelling (FDM). FDM is a filament based rapid prototyping system (80). The application of FDM demands that the material can be made in feedstock filament form.

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A single screw extruder was used to fabricate the filaments from the composite. The glass transition of the composite was found to be 126°C, which is higher than that of pure ABS material. In addition, the melt flow behavior was extensively studied by setting up a finite element model (79).

8.5

Applications

ABS resins have high durability and hence are used as basic materials in the production of parts for uncountable products, such as computer housings, television sets, and automobiles (81). Subsequently, we restrict the discussion to applications that emerged more recently and that might be less common to the reader. 8.5.2

Foam Stops

Rigid poly(vinyl chloride) (PVC) foam has commonly been used to make foam stops for windows. However, this foam type may be relatively expensive, and it may not provide the desired physical characteristics. ABS foam compositions have been developed that contain about 10 parts of a foam modifier and 0.5-2.0 parts of a blowing agent. Sodium bicarbonate is a suitable blowing agent. The foaming modifier is preferably adapted to decrease the foam density and to increase the foam swell of the composition (82). In particular, the foam modifier consists of SAN. The ingredients are admixed and then extruded. Articles with a specific gravity of 0.3-0.47 g cm" 3 are obtained. 8.5.2

Electroconductive

Resins

Electroconductive resin compositions, which are useful for packaging electronic devices, have been described. In general, electroconductive resin compositions are made up from a thermoplastic resin and an electroconductive filler, mostly carbon black. Poly(phenylene ether) resins are known to impart heat resistance. For general purposes, a poly(styrene) (PS) resin and an ABS resin are superior to other resins in that even if carbon black is incorporated in a large amount, there will be no substantial decrease in the flowability or

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moldability, and they are advantageous also from the viewpoint of costs. In these compositions, a common drawback is that carbon black is likely to fall off from the surface of a molded product by abrasion. Special formulations composed from a variety of resin components that overcome this drawback have been developed (83). In this way, contamination of integrated circuits (IC)s, etc., to be caused by falling off of carbon black, by abrasion when contacted with ICs can be substantially reduced. 8.5.3

Tunable Magneto Rheological

Compositions

A magneto rheological elastomer consists of an elastomeric host or a matrix material filled with iron or other magnetizable particles. The addition of magnetizable particles to the matrix produces an elastomer whose mechanical properties can be rapidly and continuously controlled with an applied magnetic field. The strength of such an elastomer can be characterized by its field-dependent modulus. In particular, a magneto rheological elastomer is a field-controllable material with tunable stiffness and damping characteristics, which makes it useful for vibration isolation and damping applications. Magneto rheological elastomers may have aligned or randomly arranged magnetizable particles in a thermoset or thermoplastic matrix. The thermoplastic matrix may be, among others, an ABS type polymer (84). The magnetizable particles may be coated to reduce corrosion or to improve the bonding between the particle and the matrix. 8.5.4

Cement

Additive

Cementing compositions that can provide greater elasticity and compressibility, while retaining high compressive and tensile strengths have been formulated. Major applications are targeting to seal subterranean zones penetrated by a well bore. Such cementing compositions are obtained by adding ABS types to common cements used in subterranean applications (85, 86). When ABS is added to water-extended slurries, a cementing composition is created with a lower Young's modulus while achieving high compressive and tensile strengths.

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Engineering Thermoplastics: Polyolefins and Styrentcs

It has been speculated that the AN in ABS hydrolyzes in the cement slurries and generates carboxylates, which facilitate bonding of the normally incompatible elastomer to the cement. Such bonding may allow dissipation of imposed stresses, thus preventing brittle failure of the cement sheath. 8.5.5 Membrane

Materials

The chemical structure of ABS suggests that ABS would allow to reach high permeation fluxes because of its rubbery regions and high separation factors due to the glassy matrix. The sorption and the permeation of pure CO2, CH4, N2 and O2 through an ABS membrane (Lustran® 246) have been measured (87). Since glassy polymers tend to become plasticized by CO2, it is important to determine the magnitude to which CO2 effects plasticization. This is achieved in monitoring nonlinear effects of gas permeability of mixtures containing CO2. CO2 shows a higher sorption than expected. This is attributed to the presence of acrylonitrile moieties in the ABS copolymer. In the system N2/O2, the ABS membrane shows a high selectivity. This property makes this polymeric material attractive as a gas separation membrane for N2 and O2 at moderate temperatures. 8.5.5.1 Blends and Coatings Poly(ethersulfone) (PES) is widely used for the preparation of membranes, including ultrafiltration, nanofiltration, and reverse osmosis membranes (88). However, PES lacks hydrophilic groups and the membrane material must be therefore modified. Therefore, in order to increase the separation performance towards to metal ions, ABS can be introduced to a PES membrane. Among the constituent components, styrene, and 1,3-butadiene are hydrophobic, but acrylonitrile is hydrophilic. In addition, ABS contributes to the strength, rigidity and toughness of the membrane (89). In addition to ABS, membranes using a polymer blend of chitosan and ABS with glutaraldehyde as a crosslinking agent have been used as coating materials for PES ultrafiltration membranes (90). Chitosan is the deacetylated form of chitin. Chitin is the second most occurring polymer in nature behind cellulose. Chitosan is an

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extremely hydrophilic material due to reactive amino and hydroxyl groups. It has been shown that when the ABS content is increased in the blend, the surface of the membranes become dense, and the membrane porosity decreases (90). Concomitantly, a higher ABS content decreases the amorphous nature, which in turn lowers the permeate flux of the membranes. 8.5.5.2 Mixed Matrix Membranes Mixed matrix membranes have been prepared from ABS and activated carbons. The membranes are intended for gas separation. A random agglomeration of the carbon particles was observed. A close interfacial contact between the polymeric and filler phases was observed. This morphology between inorganic and organic phases is believed to arise from the partial compatibility of the styrene/butadiene chains of the ABS copolymer and the activated carbon structure. A good permeability and selectivity for mixtures of carbon dioxide and methane has been reported (91,92). 8.5.5.3

Pervaporation Membranes

Anhydrous hydrazine is used as a rocket propellant. It is obtained by the dehydration of hydrazine hydrate. However, hydrazine forms an azeotrope with water, which makes conventional processes of purification expensive. Purification of hydrazine by pervaporation techniques could be an alternative process. Since hydrazine is highly alkaline, the proper selection of the polymer for the pervaporation membrane is important. A series of membrane materials have been tested for the performance of water removal from hydrazine, including poly(vinyl alcohol) (PVA), ethyl cellulose, PS, and ABS (93). Contact angle measurements served to estimate the hydrophilic or hydrophobic properties. Apolar materials showed higher separation factors than polar materials. Encouraging results with respect to the performance were obtained with modified ethyl cellulose and ABS membranes.

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8.5.6 Electroless Plating Metallization of plastics can be achieved by (94): 1. 2. 3. 4.

Vacuum metallization or vapor deposition, Indirect metallization, Electroplating, and Electroless plating.

Metal-plated plastics find use in the automotive industry, hardware, plumbing fixtures, knobs, and electronic applications (95). In order to metallize a polymer surface, electroless plating can be applied. This process typically consists of a pretreatment process in order to improve the adhesion. In the second step a surface seeding of the electroless catalyst is done. Wet chemical methods of pretreatment are using strong acids such as chromic acid, sulfuric acid and acidified potassium permanganate in order to achieve a surface modification of the polymers (96). The presence of chromium may impose serious environmental problems, because of the known toxicity of Cr 6+ . For this reason attempts have been undertaken to develop methods that work without using chromium compounds (95). Alternatively, for an ABS polymer, a photocatalytic reaction can be applied as a pretreatment method prior to electroless plating. Unlike the conventional wet chemical method, this method can improve the adhesion strength without severe morphological changes (96). The pretreatment method uses a photocatalytic reaction in a T1O2 dispersed solution. The photocatalytic reaction occurs by the formation of an electron-hole pair in a semiconducting material when the photon energy exceeds the band gap. Thus the photogenerated holes react readily with water and hydroxyl ions adsorbed in forming hydroxyl radicals. The hydroxyl radicals in turn act as oxidizing agents (97,98). Copper has been successfully deposited onto aluminum seeded ABS articles (99). Acidic electroless baths have been used with 15% copper sulfate and 5% of e.g., sulfuric acid, phosphoric acid, nitric acid, or acetic acid. The deposition has been carried out both at room temperature and at 60°C. As expected, the deposition rate is dramatically increased at elevated temperatures.

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Table 8.10: Electrical Surface Resistance of the Layers from Different Acidic Baths at 60°C (99) Deposition time/[min] 20 30 60 120 180

Resistance/IP cm -2] CH3COOH H 2 S0 4 H3PO4 79E4 1.10 0.90 0.03 0.08

145 5.4 0.20 0.10 0.06

534 8.8 1.2

In all of the four acidic baths on the seeded ABS surfaces copper crystals were obtained. However, conductive copper layers were obtained only from the H 2 S0 4 / H3PO4, and CH3COOH baths, but not from a HNO3 containing bath (99). The electrical surface resistance of the copper layers from different acidic baths after different depositions times is shown in Table 8.10. The adhesion was measured using the ASTM standard tape test (100). The adhesion of the conductive copper layers proved to be excellent. 8.5.7 Encapsulation Shells for Phase Change Materials A phase change material is a substance with a high heat of fusion. By melting and solidifying at a certain temperature, it is capable of storing and releasing large amounts of energy. Phase change materials are used basically for the storage of thermal energy They have a wide range of applications, including: • Conditioning of buildings and vehicles, • Cooling and thermal protection of food, and • Recovery heat generated by various processes. The basic principles of the thermal energy storage with phase change materials have been reviewed (101). Microencapsulation of phase change materials protects the core materials in as this process (102): • Reduces the reactivity of phase change materials with the environment,

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Engineering Thermoplastics: Polyolefins and Styrenics • Increases the heat transfer area, and • helps to withstand frequent volume changes as the phase change occurs

n-Tetradecane has been used as core material. In the first step, microcapsules were prepared as follows (103). n-Tetradecane and the shell material, such as ABS was dissolved in dichloromethane, in order to prepare the oil phase. This oil phase solution was dropped in an aqueous PVA solution and the mixture was emulsified by mechanical stirring. Then the emulsion was heated to 40°C to remove the dichloromethane solvent. Eventually, the solid was separated and washed several times by deionized water and dried. Important for the success in the preparation a proper shell are the ternary phase diagrams of the shell polymer, the core n-tetradecane and the solvent dichloromethane. These phase diagrams were assessed accurately in preliminary studies, since the phase separation method is based on the precipitation of a shell material from the phase behavior of the ternary system. Actually, the core material served as a poor solvent for the shell polymer. During evaporation of the solvent, a precipitation of the shell polymer on the surface of core droplets occurs. In order to obtain microcapsules with the high solid content, a ternary solution with high concentration of the shell polymer and the core material should be chosen. 8.5.8 Hydrogen Storage AB5 alloys are intermetallic compounds with hexagonal crystalline lattice. Constituting compounds are inter alia rare earth metals. These compounds are capable to form hydrides as the dissolve hydrogen. Hydrogen storage alloys of the AB5 type have high initial activation, good charge stability and relatively long charge-discharge cycle life, but at the same time they have a low discharge capacity. For enhancement of the life a low concentration of cobalt, zirconium of silicon may be introduced (104). AB5 metal hydride particles have been dispersed in a polymer matrix in order to entrap the micro and nanoparticles produced by repeated fragmentation processes of the metal phase during the

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Table 8.11: Capacities of Carbonaceous Materials Origin of carbon Epoxy novolak resin Resol resin Quinoline pitch Poly(acrylonitrile) Acrylonitrile-butadiene -styrene Mesocarbon from pitch coal Pinecone hull Graphite Poly(p-phenylene) Resorcinol (aerogel)

Capacity/[mAh g '] 570 550 320 426 564 1660 394 372 780 1290

Reference (105) (105) (105) (105) (105) (106) (107) (108) (108) (109)

hydrogen charging and discharging cycles. ABS was chosen as matrix polymer. AB5/ABS composite pellets have been produced by using a dry mechanical particle coating method (110). It was shown that the AB5/ABS composite tolerated the hydrogénation effects on metal particles, with no losses in hydrogénation kinetics. The results indicated that the compositions are suitable for metal hydride based hydrogen storage devices. 8.5.9

Carbon Materials

The search for new anode materials that satisfy the requirements of commercial lithium ion batteries has been a long-standing challenge in industrial and academic research. In lithium rechargeable batteries carbon materials are used that function as a lithium reservoir at the negative electrode. Reversible intercalation, or insertion, of lithium into the carbon host lattice avoids the problem of lithium dendrite formation and provides a large improvement in terms of cycleability and safety (111). Non-graphitic carbon materials that can be obtained from synthetic polymers by pyrolysis are of particular interest. The capacities of carbonaceous materials are summarized in Table 8.11. ABS decomposes in a rapid single step reaction, which is complete around 600°C. Disordered carbon materials were synthesized by the pyrolysis of ABS at 600,700,800 and 900°C in an argon atmosphere. The heating rate was l°C/min for a soak period of 1 h.

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X-ray diffraction studies suggested a disordered carbon structure with a large number of single layer carbon sheets. By varying the soak time, pyrolysis temperature, and heating rate, the compositional, structural, and electrochemical characteristics of the carbonaceous products may be tailored in a wide range. Charge-discharge studies of the product obtained by a 1 h pyrolysis at 600°C at a heating rate of 20°Cmin _1 exhibited first-cycle lithium insertion and deinsertion capacities of 825 and 564 mAh g" 1 , respectively. Subsequent cycles showed a remarkable improvement in cycling efficiency with a 10th cycle efficiency of 100% (105).

8.6

Suppliers and Commercial Grades

Examples for commercially available ABS polymers and suppliers as well are shown in Table 8.12. Tradenames appearing in the references are shown in Table 8.13.

8.7

Safety

In general, polymerization reactions have to be to performed with care. Based on the fact that Taiwan has the largest ABS copolymer production in the world, a group originating from there has presented a study on possible hazards that might arise in the course of the polymerization process (112,113). The prevention of unexpected exothermic reactions and related emergency relief hazard is essential in the safety control of ABS emulsion polymerization. Various scenarios were verified from abnormal conditions, including (113): • • • • •

Loss of cooling, Double charge of initiator, Overcharge of monomer, No charge of solvent, and External fire.

Based on these studies, certain safety precautions have been suggested. For example, a venting diameter of 2.35-2.85 inch was suggested for an existing ABS copolymerization reactor in case of double

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Table 8.12: Examples for Commercially Available ABS Polymers Tradename

Producer

ABEL ABS Absrtron

Hongjinyin Industry Bhansali Engineering Polymers Ltd. Westlake Plastics Comp. Albis Plastic GmbH Marplex Australia Pty. Ltd. SABIC Innovative Plastics SABIC Innovative Plastics Bayer Material Science AG Chemturea Daicel Polymer Ltd. Clariant Performance Plastics Delta Polymers DENKA Cossa Polimeri S.r.l. TP Composites, Inc. Nippon A&L Inc. Korea Kumho Petrochemical Co., Ltd. LG Chem Ltd. NEOS ABS Dow Plastics Per rite Romira GmbH Cheil Industries, Inc. Asahi Kasei Corp. BASF BASF Toray Resin Comp. UMG ABS, Ltd. PlastxWorld Inc. PlastxWorld Inc. DSM Engineering Plastics

Absylux Alcom® ABS Asta lac AVB* Cyclolac Bayblend Blendex Cevian®... Clariant ABS Delta ABS Denka ABS Estad iene Hifill® ABS Kralastic Kumho ABS LG ABS Lustran® ABS Magnum™ Ronfain® Rotee® Starex® Stylac® Terblend® Terluran® Toyolac® UMG® ABS Verolloy B Veroplas Xantar®

Remarks

ABS + PA6

ABS + PBT ABS

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Polyolefins

and

Styrenics

Table 8.13: Tradenames in References Tradename Description

Supplier

Bayer AG Bayblend® FR2010 PC/ABS terpolymer (78) Blendex® 446 General Electric Batch of SAN and Teflon (21) Blendex® ABS General Electric ABS copolymer (85,86) Disflamoll® TP Bayer AG Triphenyl phosphate (67,77) Fyrolflex® RDP Akzo Nobel Tetraphenyl resorcinol diphosphite (67,78) Hercoprime® Hercules Inc. Maleic-anhydride-grafted PP (19) Lustran® Bayer AG ABS copolymer (87) Makroion® Bayer AG Poly(carbonate) (19) Novodur® Bayer ABS (64) Nyglos® Nyco Minerals Inc. Wollastonite (67) Pebax® Arkema Poly(amide imide) (antistatic agent) (87) Pervap® Sulzer Chemtech Ltd. Pervaporation membrane, PVA, Silicone (93) Silres® SY 300 Wacker Silanol-functional solid phenyl propyl polysiloxane (77) Teflon® 30 N DuPont PTFE emulsions (21,22,67,77) Teflon® Dupont Tetrafluoro polymer (68) Wolkron® Heinrich Osthoff-Petrasch GmbH Wollastonite (67)

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charge of monomers, which might lead to thermal runaway. More details are presented in the original literature (113). In 1997, in Taiwan, silos containing ABS powder exploded. The accident was analyzed critically. In particular, the materials were SAN and ABS with a low and high content of poly(butadiene) latex (PBL). Initially, it was believed that the explosion was caused by a thermal runaway, however this hypothesis was rejected after closer analysis. Finally, a dust explosion was proposed as the cause of accident. A brush discharge was located as a possible ignition source for the dust explosion (114). This kind of discharge can exist both in granules and fine powders. The probability of the occurrence of a brush discharge increases with increasing size of the container, filling rate and charge-to-mass ratio (115).

8.8

Environmental Impact and Recycling

Basically, there are two ways of recycling, namely, material recycling and recycling via a chemical reaction, the latter using mostly thermal processes. Of course, these two methods can be further subdivided. There are monographs on the basic aspects of recycling of plastics (116,117). 8.8.2

Material

Recycling

8.8.1.1 Mechanical Recycling From articles used in electronics, high value precious metals, electronic components and glass electronic components are separated from the plastic housings, which have been generally sent to landfill because there was no economical process to separate the plastics to sufficient purity to enable the plastics to be recycled. The housings are generally made of mixed plastics such as ABS and PC (118). Methods suitable for the recycling of ABS resins have been developed (81,118-120). The recycled ABS resin obtained by recycling an ABS resin can be formed into articles by injection molding in combination with a virgin material.

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Engineering Thertnoplastics: Polyolefins and Styrenics

Initial Steps. The process for recycling articles into the recycled ABS resin is a combination of grinding, washing, drying and foreign matter removal. The conditions of these steps must be carefully optimized in order to produce a recycled ABS resin having the desired properties with good productivity. The raw material ground to the predetermined size is passed through a magnetic separator in order to capture ferromagnetic metals inside the ground material. Ceramics, metal oxides and the like higher in true density than the recycled ABS resin are gravity-separated by precipitation in a washing fluid such as water. Automatic Product Identification. A recycling system for magnetic recording products has been presented with a sophisticated method of automatic product identification (81). Products or parts that are to be disposed are in the first step roughly classified into product groups. Then, plastics constituting the products or parts are identified by FTIR. The identification is conducted with respect to the transparent resin portions. When the transparent resin is identified to be containing PS, it is concluded that another resin mixed is HIPS, and, on the other hand, when the transparent resin portion is comprised of SAN, it is judged that another resin admixed is ABS (81). The measurement and separation by FTIR proceeds quickly. Floating. Another method for separating ABS and PC relies on the selective modification of the effective density of one or more of these plastics in a solution in which the shredded plastic materials are dispersed so as to cause a certain fraction to float and another fraction to sink. Thereafter, this procedure may be repeated a number of times, in each varying either or all of the parameters of specific gravity, surface tension and pH in order to successively float a portion of the material causing the remaining material to sink. The floated material can be separated from the material, which sinks, until eventually all desired material or substantially all the desired material has been removed and segregated (118). Each separation module includes a separation tank, a feeding section for feeding of mixed stream into the separation tank, and a collecting section for collecting of the separated mixed plastics including floaters and

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sinkers from the separation tank. The separation tank has no moving parts. Each separation tank and the first stage initial washing tank is a standard off-the-shelf circular tank with a flat bottom. Washing and drying steps are eliminated between separation stages. Batch processing can be replaced with an essentially continuous operation. An integrated vibrating screen and air classification system is provided (121). Examples of mixed post-consumer plastic waste by the combination of a three-stage sink-float method and selective flotation have been presented. The appropriate conditions, e.g., wetting agents, frother, depressant, and pH condition, are of importance (122). Hydrocyclone. The effectiveness of a hydrocyclone system for the separation of plastics, using both water and calcium chloride solutions, has been investigated (123). The effective density of separation depends on the particle size and aspect ratio. As the particle size and aspect ratio decreases, the separation becomes more efficient and the offset between separation density and hydrocyclone medium density decreases. This findings suggest that for efficient density separation closely sized fine plastic fractions are required. The removal of a high density plastic such as PVC from HIPS, ABS), and poly(ethylene) can be readily achieved using a hydrocyclone. Also, a partial separation of HIPS from ABS is possible (123). A special kind of flotation is froth flotation (124). Selective depressants for the separation of ABS and HIPS have been used. Acetic acid, methanol and quebracho have been probed as selective wetting agents for froth flotation. All these compounds are potentially selective agents, provided the particles are of similar size. The use of quebracho at pH 11 gave the most promising results as selectivity was seen over a wide particle size range. Triboelectrification. In triboelectrification, plastics are brought into repeated contact resulting in a loss or gain electrons depending on the relative dielectric constant of the materials (125). In the case of ABS and HIPS, ABS exhibits the higher dielectric constant. Therefore ABS should become positively charged. Once materials have been

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Engineering Thermoplastics: Polyolefins and Styrenics

charged, a separation can be achieved by attraction to oppositely charged plates.

Final Steps. Finally, the process for producing a recycled ABS alloy resin consists of (120): 1. Blending the recycled ABS resin with another resin including PC, PVC, or PBT, 2. Melt-mixing the blend obtained in the first step, and 3. Pelletizing the melt mixture thus obtained. In addition, ABS that has been recovered can be recycled into high value composites without separation from impurities. This has been exemplified with wood-plastic composites that contain ABS as matrix polymer. Both virgin ABS and recycled ABS were used and the properties of the materials were compared (126). In order to increase the performance, coupling agents were used, all based on grafted maleic anhydride. In close context to recycling emerges the question, how the properties of recycled products are changing. Studies have been performed in that ABS grades have been multiply processed by injection molding. A grade of low viscosity low and a grade of high viscosity was probed (127). It turned out that these two grades are behaving differently. The low viscosity grade shows a reduction of viscosity with the number of processing cycles. In contrast, the high viscosity grade shows an increase of melt viscosity after repeated processing. In the first case it is assumed that degradation reaction are taking place, whereas in the second case, obviously, crosslinking reactions are dominant. The shear rates and temperatures in the injection molding affect behavior of the materials (127). Recycled ABS can used as an additive that increases the compressive modulus of cement mortars. Unfortunately, ABS increases the porosity in the mortar. This effects a decreased adhesion strength to steel. However, by treating the ABS with maleic anhydride, a substantial increase in adhesive strength is obtained (128).

Acrylonitrile-Butadiene-Styrene 8.8.1.2

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251

Dissolution Recycling

Solvent-based recycling processes can separate plastics from other types of waste by selective dissolution. In particular, polymers of different chemical constitution can be separated and also blends of polymers (129). In the course of the dissolution process, it is possible to modify the polymer, since additional components could be incorporated during the dissolution. Except for heating during the dissolution process, there is no danger of further degradation in the recycling process. In particular, no shear-stress arises as in melt recycling. However, in the dissolution process some disadvantages arise, e.g., due to the toxicity of solvents. As study has been presented in order to examine the effect of consecutive dissolution cycles on the mechanical properties of ABS. In a preliminary work the dissolution conditions were elucidated. Subsequently, the mechanical properties of ABS were assessed after each dissolution cycle (129). In the first stage the ABS was cut in order to allow faster dissolution. Then, the dissolution was carried out using a specific solvent and temperature. The recovery of dissolved ABS was carried out by precipitation/filtration techniques or simply by the evaporation of the solvent. Eventually, the recycled ABS compound was cut again to an average size of 2-3 mm, and the dissolution process was repeated. The whole process was repeated several times. A lot of solvents and non-solvents for ABS are known. Among these solvents, acetone and tetrahydrofuran (THF) were chosen, because these solvents dissolve ABS already at room temperature. Therefore, the costs of the recycling process and further the risk of thermal degradation during the process are decreased. Acetone is somewhat more advantageous then THF because of the costs of the solvent. It is told that a recycling process by dissolution is only industrially feasible if the dissolution time is less than 90 min. Acetone allows the dissolution in a shorter time. The dissolution time of ABS in acetone as a function of concentration at room temperature is shown in Figure 8.6. From thermogravimetric analysis it became obvious that during

Engineering Thermoplastics: Polyolefins and Styrenics

252 80 -i

/

70 /^

60 1

Έ

/

5

V °E ¡-

/

30 -

10

S*

S\

40-

20 -T—

/

^ ^ 1

1

1

1

1

1

15

20

25

30

35

40

Concentration [g/dl] Figure 8.6: Dissolution Time of ABS in Acetone as a Function of Concentration (129) the dissolution process certain stabilizers could be removed, which cause a change in the properties of the material. Recycled ABS appeared to be darkened. This was attributed to a degradation of 1,3-butadiene, suggested by FTIR studies. In summary, the mechanical behavior of the recycled ABS is changing in some aspects. Young's modulus is not affected, but yield stress and impact strength, are found to be reduced. These properties drop in the first recycling step, and remain essentially constant in successive recycling cycles. 8.8.2

Pyrolysis

Among the most frequently used nitrogen containing polymers in electrical, electronic, and automotive applications are PA and ABS. Pyrolysis proved to be a suitable method for recycling plastic waste. A disadvantage is that the pyrolysis results in a broad palette of products of reaction, which makes the direct use of the products as monomers difficult. A remarkable exception is poly(methyl meth-

Acrylonitrile-Butadiene-Styrene

Polymers

253

acrylate) which decomposes into more than 95% of the monomer, i.e., methyl methacrylate. 8.8.2.1 Kinetics Kinetic data on the thermal degradation of ABS and PC/ABS blends are available (130,131). Thermogravimetric analysis suggests that the kinetics of the thermal degradation can be modelled by an autocatalytic process. The fundamental kinetic equation reads as I n — + -Ï- = l n - + nln(l-a)

+ mlna.

(8.2)

In Eq. 8.2 a is the conversion, E„ is the apparent activation energy, A is the Arrhenius factor, ß the heating rate and n, m are kinetic parameters. The apparent activation energies obtained from the thermogravimetric data are essentially unaffected by the heating rate. This suggests that the most important process in the degradation of these materials arises from reactions in the ABS component. In contrast, in mixtures with a high PC content a clear increase in the apparent activation energies with heating rate is observed. This is interpreted as the thermal degradation mechanism in samples dominated by PC is composed of several complex processes, each of these mechanisms becomes predominant during different stages of the overall process (131). 8.8.2.2

Products ofPyrolysis

In the course of thermal degradation of ABS a lot of nitrogen containing compounds are produced, as shown in Table 8.14. Inspection of Table 8.14 reveals that a lot of nitrogen containing products are among the products of pyrolysis. Styrene is the most significant product or thermal decomposition. Also dimers and trimers from styrene and monomeric acrylonitrile are main products in the pyrolysis oil.

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Engineering Thermoplastics: Polyolefins and Styrenics

Table 8.14: Thermal Decomposition Products of ABS at 550°C (132) Compound Acrylonitrile Toluene Styrene Methylstyrene 2,4-Dinitrilebut-l-ene (Acrylonitrile dimer) 2-Nitrile-4-phenylbut-l-ene 2-Phenyl-4-nitrilebut-l -ene 2,4-Diphenylbut-l-ene (Styrene dimer) 2,6-Dinitrile-4-phenylhex-l-ene 4,6-Dinitrile-2-pheny lhex-1 -ene 2-Nitrile-4,6-diphenylhex-l -ene 4-Nitrile-2,6-diphenylhex-l -ene 2,4,6-Tripheny lhex-1-ene (Styrene trimer) 8.8.2.3 Catalysts Actually, catalytic hydrodenitrogenation is an industrially applicable process for reducing the level of nitrogen content in mineral feed-stocks. For this reason, catalytic pyrolysis was investigated as an alternative process also, in order to minimize the problems of heterogeneity of the products (132). Several zeolites were used both in original and calcined form. The volatile products of pyrolysis either analyzed directly by GC/MS or after passing over the respective zeolites. The pyrolysis gas chromatogram of ABS at 550°C changes considerably when the pyrolysis products are passed over zeolite catalysts. The specific activity towards certain reactions, e.g., cyclization, aromatization, or chain cleavage is somewhat dependent on the nature of the individual zeolite. In general, enhanced benzene, toluene, ethylbenzene at the cost of dimer, trimer formation is observed. Nitrogen containing compounds do not appear in the pyrolysis oil after catalytic conversion. However, the product gas is rich in nitriles (132). In an analogous way as described above, in the case of ABS polymers that are equipped with bromine containing flame retardants, pyrolysis oils with low bromine content can be obtained (133). This issue is important for processing scrap plastics from waste of elec-

Acrylonitrile-Butadiene-Styrene

Polymers

255

trical and electronic equipment by pyrolysis. The presence of zeolite catalysts increases the amount of gaseous hydrocarbons produced during pyrolysis but decreases the amount of pyrolysis oil. Further, significant quantities of coke were formed on the surface of the catalysts in the course of pyrolysis. The catalysts reduced the yield of e.g., as styrene and cumene, in favor of naphthalene. The zeolite catalysts, especially Y-Zeolite, were found to be very effective in removing volatile órgano bromine compounds. However, they were less effective in removing antimony bromide from the highly volatile products of pyrolysis (133). 8.8.2.4

Municipal Waste

Municipal waste plastic is a mixture of polymers, which contains about 3-5% ABS (134). Mixtures similar to the composition of a typical municipal waste, containing high density poly(ethylene), PP, PS and ABS with a brominated flame retardant were thermally degraded at 450°C. It was found that the majority of the bromine was concentrated in the carbon residue and while majority of the nitrogen accumulates in the liquid products irrespective of degradation conditions (134). Besides a large amount of styrene and benzene derivatives the pyrolysis oils contained around 1000 ppm of nitrogen, 1000-4000 ppm bromine, 5000-5200 ppm chlorine and 800-1300 ppm oxygen (135). PVC is acting particularly in the early stages of pyrolysis whereas PET is active in all stages of the process. PET has a different effect in comparison to PVC, as it strongly increases the amount of nitrogen being converted into hydrogen cyanide. Further, the amount of bromine entering the liquid, wax and carbon residue is increased (135). Iron-based catalysts (136) increase the initial degradation rate. Moreover, it was found that iron-based catalysts remove the bromine from the pyrolysis oil and decrease the nitrogen content in the oil fraction by converting the nitrile moieties into ammonia (137). The nitrogen balance is dependent on the catalyst used for degradation (138). The nitrogen balance for ABS is shown in Table 8.15. The ABS component and its flame retardant interact with both PVC and PET in the course of thermal decomposition (135,139).

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Table 8.15: Nitrogen Balance of ABS at 450°C (138) Catalyst

% of Original nitrogen Gas Oil HCN Organic NH 3 HCN

1.27 Thermal 5.07 SA4 8.59 1.95 1.47 SA4/y-Fe 2 0 3 11.84 SA4/Fe 3 0 4 -C 10.61 1.77 SA4/a-FOOH 6.29 0.81 SA4: Si0 2 /Al 2 0 3 , mole ratio of 0.42,,

Residue

31.37 2.92 59.37 3.56 24.90 61 2.09 19.46 65.14 2.27 21.01 64.34 2.20 23.41 67.29 specific surface area 240 m 2 g

References 1. J.L. Amos, The SPE international award address - 1973 the development of impact polystyrene-a review, Polym. Eng. Sei., 14(1):1—11, 1974. 2. J. Scheirs, "Historical overview of styrene polymers," in J. Scheirs and D. Priddy, eds., Modern styrenic polymers: Polystyrenes and styrenic copolytners, Wiley Series in Polymer Science, chapter 1, pp. 3-24. John Wiley, Chichester, 2003. 3. R.N. Haward and E. Joyce, Suspension polymerization process, US Patent 2 668 806, assigned to Styrene Products Ltd., February 09,1954. 4. J.L. Amos, M.J. Lloyd, and M.O. Ray, Method of making linear interpolymers of monovinyl aromatic compounds and a natural or synthetic rubber, US Patent 2 694 692, assigned to Dow Chemical Co., November 16,1954. 5. W.C. White, Butadiene production process overview, Chem. Biol. Interact, 166(1-3):10-14, March 2007. 6. R. Vanspeybroeck, R.P Dion, and J.M. Ceraso, "High heat resistant ABS technology," in J. Scheirs and D. Priddy, eds., Modern styrenic polymers: Polystyrenes and styrenic copolymers, Wiley Series in Polymer Science, chapter 15, pp. 321-340. John Wiley, Chichester, 2003. 7. H. Eichenauer, E. Wenz, H. Alberts, U. Jansen, and H.-E. Gasche, ABS moulding material with improved workability and a high lustre, US Patent 7074854, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), July 11,2006. 8. VA. Aliberti, R.L. Kruse, and E.M. Valcarce, Mass polymerization process for ABS polyblends, US Patent 4 598124, assigned to Monsanto Company (St. Louis, MO), July 1,1986. 9. G.-S. Kim, C.-H. Lee, B.-T. Yang, and J.-B. Chai, Method for preparing acrylonitrile-butadiene-styrene latex having high total solid content,

Acrylonitrile-Butadiene-Styrene

10. 11. 12.

13. 14. 15. 16. 17. 18.

19. 20.

21. 22.

Polymers

257

US Patent 6753382, assigned to LG Chemical Co., Ltd. (Seoul, KR), June 22, 2004. J.-I. Kim and W.C. Wu, Process for making ABS polymeric blends, US Patent 6492467, assigned to Bayer Corporation (Pittsburgh, PA), December 10, 2002. T.L. Virkler and W.C. Wu, Process f or preparing extrusion grade ABS polymer, US Patent 6528591, assigned to Bayer Corporation (Pittsburgh, PA), March 4, 2003. Y.-C. Sun, Method for the preparation of alkenyl aromatic monomer nitrile copolymer reinforced with rubbery copolymer, US Patent 4387179, assigned to The Dow Chemical Company (Midland, MI), June 7,1983. R.P. Dion, D.W. Mitchell, and P.B. Leng, Process for the preparation of multimodal ABS polymers, US Patent 5 955 540, assigned to The Dow Chemical Company (Midland, MI), September 21,1999. H. Eichenauer, Highly impact-resistant ABS moulding materials, US Patent 6407163, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), June 18, 2002. D.E. Henton and T.M. O'Brien, Particle agglomeration in rubber lárices, US Patent 4419496, assigned to The Dow Chemical Company (Midland, MI), December 6,1983. H. Eichenauer, Thermoplastic moulding materials based on special highly effective grafted polymer components, US Patent 6767963, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), July 27,2004. R.J. Pingel, G.P. Onifer, and T.L. Spencer, Method for recovering synthetic resinous latex solids, US Patent 4 299 952, assigned to The Dow Chemical Company (Midland, MI), November 10,1981. S. Vilasagar, V. Lowry, D.M. Ferraris, K. Feng, R.E. Colborn, M.H. Littlejohn, and D.F. Townsend, Enhanced polymerization process, US Patent 6784253, assigned to General Electric Company (Pittsfield, MA), August 31, 2004. S.C. Tjong and Y.Z. Meng, Effect of reactive compatibilizers on the mechanical properties of polycarbonate/poly(acry!onitrile-butadiene-styrene) blends, Enr. Polym. ) . , 36(1):123-129, January 2000. D. Wittmann, H. Peters, J. Schoeps, H.-J. Kress, J. Buekers, and K.-H. Ott, Flame-retardant, high-impact polycarbonate molding compounds, US Patent 5061745, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), October 29,1991. M. Zobel, T. Eckel, T. Derr, and D. Wittmann, Flame-resistant polycarbonate ABS blends, US Patent 6528561, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), March 4,2003. E. Wenz, T. Eckel, O. Meincke, H. Warth, and H. Eichenauer, Polycarbonate molding compositions with improved hydrolysis resis-

258

23.

24.

25.

26.

27. 28.

29. 30.

31.

32.

33.

Engineering Thermoplastics:

Polyolefins

and

Styrenics

tance, US Patent 7358290, assigned to Bayer Material Science AG (Leverkusen, DE), April 15,2008. Y. Matoba, Y. Shimizu, K. Miura, S. Kitano, T. Sakashita, and H. Tanaka, Antistatic resin blends comprising ABS graft copolymers and ethylene oxide copolymers, US Patent 5556916, assigned to Daiso Co. Ltd. (Osaka, JP), September 17,1996. K. Maeda, T. Takemoto, M. Fujii, Y Fukui, and Y. Urata, Thermoplastic resin composition and moldings thereof, US Patent 7589142, assigned to UMG ABS, Ltd. (JP) Ube Industries, Ltd. (JP), September 15, 2009. O. Meincke, D. Kaempfer, H. Weickmann, C. Friedrich, M. Vathauer, and H. Warth, Mechanical properties and electrical conductivity of carbon-nanotube filled polyamide-6 and its blends with acrylonitrile/butadiene/styrene, Polymer, 45(3):739-748, February 2004. H. Tsuji and Y Ikada, Blends of aliphatic polyesters, i. physical properties and morphologies of solution-cast blends from poly(DL-lactide) and poly(e-caprolactone), /. Appl. Polym. Sel, 60(13):2367-2375, June 1996. H.-J. Jin, I.-J. Chin, M.-N. Kim, S.-H. Kim, and J.-S. Yoon, Blending of poly(/-lactic acid) with poly(cz's-l,4-isoprene), Eur. Polym. ]., 36(1): 165-169, January 2000. K.-S. Kim, I.-J. Chin, J.S. Yoon, H.J. Choi, D.C. Lee, and K.H. Lee, Crystallization behavior and mechanical properties of poly(ethylene oxide)/poly(l-lactide)/poly(vinyl acetate) blends, /. Appl. Polym. Sei., 82(14):3618-3626, December 2001. X. Ma, Y Jiugao, and N. Wang, Compatibility characterization of poly(lactic acid)/ poly(propylene carbonate) blends, /. Polym. Set, Part B: Polym. Phys., 44(1):94-101, January 2006. Y. Li and H. Shimizu, Improvement in toughness of poly(l-lactide) (PLLA) through reactive blending with acrylonitrile-butadiene-styrene copolymer (ABS): Morphology and properties, Eur. Polym. }., 45 (3):738-746, March 2009. M.-L. Xue, Y.-L. Yu, H.H. Chuah, J.M. Rhee, N.H. Kim, and J.H. Lee, Miscibility and compatibilization of poly(trimethylene terephthalate)/acrylonitrile-butadiene-styrene blends, Eur. Polym.}., 43(9):38263837, September 2007. W. Nielinger, H. Kauth, D. Wittmann, D. Freitag, and K.-J. Idel, Production of blend systems by the condensation of oligocarbonates in the presence of mass-polymerized ABS, US Patent 5416161, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), May 16,1995. D.E. Henton, A. Chen, P.J. Moses, B.S. Ehrlich, and D.E. Beyer, Thermally processable blends of high modulus polyurethanes and mass

Acrylonitrile-Butadiene-Styrene

34. 35. 36. 37. 38. 39.

40.

41.

42. 43. 44. 45. 46. 47.

Polymers

259

polymerized ABS resins, US Patent 5491194, assigned to The Dow Chemical Company (Midland, MI), February 13,1996. D. Stevanovic, A. Lowe, S. Kalyanasundaram, P.Y.B. Jar, and V. Otieno-Alego, Chemical and mechanical properties of vinyl-ester/ABS blends, Polymer, 43(16):4503-4514, July 2002. G.O. Shonaike, ed., Polymer Blends and Alloys, Vol. 52 of Plastics engineering, Dekker, New York, 1999. D.R. Paul and C.B. Bucknall, eds., Polymer Blends: Formulation and Performance, John Wiley and Sons, Inc., New York, 2000. L.M. Robeson, Polymer blends: A Comprehensive Review, Hanser Gardener Publications, Cincinnati, OH, 2007. N.C. Liu and W.E. Baker, Reactive polymers for blend compatibilization, Adv. Polym. Technol, ll(4):249-262, December 1992. B.M. Rao, P.R. Rao, and B. Sreenivasulu, Grafting of maleic anhydride onto acrylonitrile-butadiene-styrene terpolymer: Synthesis and characterization, Polym.-Plast. Technol. Eng., 38(5):967-977, November 1999. R. Qi, J. Qian, and C. Zhou, Modification of acrylonitrile-butadienestyrene terpolymer by grafting with maleic anhydride in the melt. I. Preparation and characterization, /. Appl. Polym. Sei., 90(5):12491254, October 2003. R. Qi, J. Qian, Z. Chen, X. Jin, and C. Zhou, Modification of acrylonitrile-butadiene-styrene terpolymer by graft copolymerization with maleic anhydride in the melt. II. Properties and phase behavior, /. Appl. Polym. Sei., 91(5):2834-2839, March 2004. R. Qi, Z. Chen, and C. Zhou, Solvothermal preparation of maleic anhydride grafted onto acrylonitrile-butadiene-styrene terpolymer (ABS), Polymer, 46(12):4098-4104, May 2005. E.A. Abdel-Razik, Photoinduced graft copolymerization of acrylamide onto styrene-butadiene-acrylonitrile copolymer, /. Photochem. Photobiol., A, 69(1):121-124, October 1992. C. Deacon and C.A. Wilkie, Graft copolymerization of acrylic acid on to acrylonitrile-butadiene-styrene terpolymer and thermal analysis of the copolymers, Eur. Polym. }., 32(4):451-455, April 1996. Z. Zhou, N. Liu, and H. Huang, Reactivity of acrylonitrile-butadienestyrene terpolymer grafted with long-chain unsaturated carboxylic acids, Polymer, 45(21 ):7109-7116, September 2004. Z.F. Zhou, H. Huang, and N.C. Liu, Kinetics and mechanism of grafting of undecylenic acid onto acrylonitrile-butadierie-styrene terpolymer, /. Polym. Sei., Part A: Polym. Chenu, 39(4):486-494, February 2001. G. Moad, The synthesis of polyolefin graft copolymers by reactive extrusion, Prog. Polym. Sei., 24(1):81-142, April 1999.

260

Engineering Thermoplastics:

Polyolefins

and

Styrenics

48. S. Sun, X. Xu, H. Yang, and H. Zhang, Toughening of poly(butylene terephthalate) with epoxy-functionalized acrylonitrile-butadiene-styrene, Polymer, 46(18):7632-7643, August 2005. 49. IDES Integrated Design Engineering Systems, The Plastics Web®, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/prospector/, 2006. 50. M.L. Shofner, F.J. Rodríguez-Macías, R. Vaidyanathan, and E.V. Barrera, Single wall nanotube and vapor grown carbon fiber reinforced polymers processed by extrusion freeform fabrication, Composites Part A, 34(12):1207-1217, December 2003. 51. D. Mari and R. Schaller, Mechanical spectroscopy in carbon nanotube reinforced ABS, Mater. Sei. Eng., A, 521-522:255-258, September 2009. 52. M. Watanabe, C. Nakata, W. Wu, K. Kawamoto, and Y. Noma, Characterization of semi-volatile organic compounds emitted during heating of nitrogen-containing plastics at low temperature, Chemosphere, 68(ll):2063-2072, August 2007. 53. B. Perret and B. Schartel, The effect of different impact modifiers in halogen-free flame retarded polycarbonate blends - ii. fire behaviour, Polym. Degrad. Stab., In Press, Corrected Proof, 2009. 54. K.H. Pawlowski, B. Schartel, M.A. Fichera, and C. Jäger, Flame retardancy mechanisms of bisphenol A bis(diphenyl phosphate) in combination with zinc borate in bisphenol a polycarbonate/acrylonitrile-butadiene-styrene blends, Thermochim. Acta, In Press, Accepted Manuscript, 2009. 55. S.V. Levchik, D.A. Bright, G.R. Alessio, and S. Dashevsky, New halogen-free fire retardant for engineering plastic applications, /. Vinyl Addit. Technol, 7(2):98-103,2001. 56. C.-C.M. Ma, A.T. Hu, and D.K. Chen, Processability, electrical and mechanical properties of EMI shielding ABS composites, Polym. Polym. Compos., l(2):93-99,1993. 57. G. Lu, X. Li, H. Jiang, and X. Mao, Electrical conductivity of carbon fibers/ABS resin composites mixed with carbon blacks, /. Appl. Polym. Sei., 62(13):2193-2199, December 1996. 58. M. Yonezawa, Surface conductive composite plastic sheet, JP Patent 8 039 734, assigned to Sumitomo Bakelite Co., February 13,1996. 59. K. Miyagawa, M. Shimizu, and M. Inoue, Conductive composite plastic sheet, JP Patent 6 305 084, assigned to Denki Kagaku Kogyo Kk., November 01,1994. 60. P.G. Kelleher, D.J. Boyle, and R.J. Miner, Photo oxidation and outdoor aging of ABS, Mod. Plast, 46(9):188,1969. 61. R. Ou, R.A. Gerhardt, C. Marrett, A. Moulart, and J.S. Colton, Assessment of percolation and homogeneity in ABS/carbon black com-

Acrylonitrile-Butadiene-Styrene

62. 63. 64.

65.

66.

67. 68. 69. 70. 71. 72.

73.

Polymers

261

posites by electrical measurements, Composites Part B, 34(7):607-614, October 2003. P. Davis, B.E. Tiganis, and L.S. Burn, The effect of photo-oxidative degradation on fracture in ABS pipe resins, Polym. Degrad. Stab., 84 (2):233-242, May 2004. M. Hie, E. Cicala, D. Grevey, S. Mattei, and V. Stoica, Diode laser welding of ABS: Experiments and process modeling, Optics & Laser Technology, 41(5):608-614, July 2009. J. Abenojar, R. Torregrosa-Coque, M.A. Martinez, and J.M. MartínMartínez, Surface modifications of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) copolymer by treatment with atmospheric plasma, Surf. Coat. Technot., 203(16):2173-2180, May 2009. H. Eichenauer, K.-H. Ott, A. Pischtschan, E. Leitz, and K.-E. Piejko, Composition of polycarbonate, ABS, a basic additive and a carboxylic and compound, US Patent 5 420181, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), May 30,1995. S.-H. Hong, Y.-H. Kweon, B.-N. Jang, Y.-K. Chang, and G.-C. Lee, Flameproof styrene-containing gra ft resin compositions having a particular nitrile content distribution, US Patent 6906123, assigned to Cheil Industries Inc. (Kyungbuk, KR), June 14, 2005. A. Seidel, T. Eckel, and D. Wittmann, Impact-resistant and flameproofed polycarbonate molding compositions, US Patent 6914090, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), July 5, 2005. J.M. McEuen, M.W. Beltz, and G. Kumar, Flame retardant polycarbonate-ABS polymer compositions, US Patent 6414060, assigned to Albemarle Corporation (Richmond, VA), July 2, 2002. D. Hoang, J. Kim, and B.N. Jang, Synthesis and performance of cyclic phosphorus-containing flame retardants, Polym. Degrad. Stab., 93(11): 2042-2047, November 2008. Z. Czégény and M. Blazsó, Effect of phosphorous flame retardants on the thermal decomposition of vinyl polymers and copolymers, /. Anal. Appl. Pyrolysis, 81(2):218-224, March 2008. S. Wang, Y Hu, R. Zong, Y Tang, Z. Chen, and W. Fan, Preparation and characterization of flame retardant ABS/montmorillonite nanocomposite, Appl. Clay Sei, 25(l-2):49-55, April 2004. A. Petsom, S. Roengsumran, A. Ariyaphattanakul, and P. Sangvanich, An oxygen index evaluation of flammability for zinc hydroxystannate and zinc stannate as synergistic flame retardants for acrylonitrile-butadiene-styrene copolymer, Polym. Degrad. Stab., 80(l):17-22, 2003. H.-C. Kao, M.-M. Lee, C.-C. Chiang, J.-L. Lin, and T.-K. Wu, Heat stabilized ABS-polycarbonate polymer blend compositions, US

262

74. 75.

76.

77.

78.

79.

80. 81.

82. 83. 84.

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Patent 5 055 505, assigned to Industrial Technology Research Institute (Hsinchu, TW), October 8,1991. S. Wang, Y. Hu, L. Song, Z. Wang, Z. Chen, and W. Fan, Preparation and thermal properties of ABS/montmorillonite nanocomposite, Polym. Degrad. Stab., 77(3):423-426,2002. J. Kim, K. Lee, K. Lee, J. Bae, J. Yang, and S. Hong, Studies on the thermal stabilization enhancement of ABS; synergistic effect of triphenyl phosphate nanocomposite, epoxy resin, and silane coupling agent mixtures, Polym. Degrad. Stab., 79(2):201-207,2003. K. Lee, J. Kim, J. Bae, J. Yang, S. Hong, and H.-K. Kim, Studies on the thermal stabilization enhancement of ABS; synergistic effect by triphenyl phosphate and epoxy resin mixtures, Polymer, 43(8):22492253, April 2002. A. Seidel, M. Wagner, J. Endtner, W. Ebenbeck, T. Eckel, and D. Wittmann, Flame-resistant polycarbonate compositions containing phosphorus-silicon compounds, US Patent 7144 935, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), December 5,2006. R.B. Durairaj and G.A. Jesionowski, Benzoylresorcinol-based phosphate ester compounds as flame retardants, US Patent 7439289, assigned to Indspec Chemical Corporation (Pittsburgh, PA), October 21, 2008. N. Mostafa, H.M. Syed, S. Igor, and G. Andrew, A study of melt flow analysis of an ABS-iron composite in fused deposition modelling process, Tsinghna Science & Technology, 14(Supplement l):29-37, June 2009. C.K. Chua, K.F. Leong, and C.S. Lim, Stratasys' Fused Deposition Modelling (FDM), chapter 4.2, pp. 124-133. World Scientific, River Edge, NJ, 2nd edition, 2003. D. Hasegawa, Y. Inagaki, H. Watanabe, and M. Sawaguchi, Recycle system for used plastic, method of reclaiming used ABS resin and reclaimed ABS resin, US Patent 7462 648, assigned to Sony Corporation (Tokyo, JP), December 9,2008. B.E. Zehner and S.R. Ross, ABS foam and method of making same, US Patent 6 784 216, assigned to Crane Plastics Company LLC (Columbus, OH), August 31,2004. T. Miyakawa, K. Ogita, M. Hiura, and M. Oda, Electroconductive resin composition, US Patent 7 261840, assigned to Denki Kagaku Kogyo Kabushiki Kaisha (Tokyo, JP), August 28,2007. A. Fuchs, F. Gordaninejad, G.H. Hitchcock, J. Elkins, and Q. Zhang, Tunable magneto-rheological elastomers and processes for their manufacture, US Patent 7 261834, assigned to The Board of Regents of The University and Community College System of Nevada on behalf of the University of Nevada, Reno (Reno, NV) N/A (, August 28,2007.

Acrylonitrile-Butadiene-Styrene

Polymers

263

85. B.R. Reddy and K.M. Ravi, Elastomeric admixtures for improving cement elasticity, US Patent 7 007 755, assigned to Halliburton Energy Services, Inc. (Duncan, OK), March 7, 2006. 86. B.R. Reddy and K.M. Ravi, Elastomeric admixtures for improving cement elasticity, US Patent 7138 446, assigned to Halliburton Energy Services, Inc. (Duncan, OK), November 21, 2006. 87. J. Márchese, E. Garis, M. Anson, N.A. Ochoa, and C. Pagliero, Gas sorption, permeation and separation of ABS copolymer membrane, /. Membr. Sei., 221(1-2):185-197, August 2003. 88. R.W. Baker, Membrane Technology and Applications, John Wiley and Sons, Inc., New York, 2nd edition, 2004. 89. M.K. Mandai, S. Dutta, and P. Bha+tacharya, Characterization of blended polymeric membranes for pervaporation of hydrazine hydrate, Chem. Eng. J., 138(1-3):10-19, May 2008. 90. A.G. Boricha and Z. Murthy, Acrylonitrile butadiene styrene/chitosan blend membranes: Preparation, characterization and performance for the separation of heavy metals, /. Membr. Sei., 339(l-2):239-249, September 2009. 91. M. Anson, J. Márchese, E. Garis, N. Ochoa, and C. Pagliero, ABS copolymer-activated carbon mixed matrix membranes for CO2/CH4 separation,/. Membr. Set., 243(l-2):19-28, November 2004. 92. J. Márchese, M. Anson, N. Ochoa, P. Prádanos, L. Palacio, and A. Hernández, Morphology and structure of ABS membranes filled with two different activated carbons, Chem. Eng. Sei, 61(16):54485454, August 2006. 93. S.V. Satyanarayana and P.K. Bhattacharya, Pervaporation of hydrazine hydrate: Separation characteristics of membranes with hydrophilic to hydrophobic behaviour, /. Membr. Sc/.,238(l-2):103-115,July 2004. 94. K.L. Mittal, ed., Metallized Plastics: Fundamentals and Applications, Proceedings of the Fourth Symposium on Metallized Plastics : Fundamental and Applied Aspects in Honolulu, Hawaii, May 17-21, 1993, Vol. 43 of Plastics Engineering, Marcel Dekker Inc., New York, 1998. 95. L.A.C. Teixeira and M.C. Santini, Surface conditioning of ABS for metallization without the use of chromium baths, /. Mater. Process. TechnoL, 170(l-2):37-^l, December 2005. 96. G.G. Kim, J.A. Kang, J.H. Kim, K.-y. Lee, S.J. Kim, and S.-J. Kim, Photocatalytic pretreatment of acrylonitrile-butadiene-styrene polymer for electroless plating, Scr. Mater., 56(5):349-351, March 2007. 97. A. Fujishima, K. Hashimoto, and T. Watanabe, T1O2 Photocatalysis: Fundamentals and Applications, BKC, Tokyo, 1999. 98. H. Schmidt, M. Naumann, T. Müller, and M. Akarsu, Application of spray techniques for new photocatalytic gradient coatings on plastics,

264

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Thin Solid Films, 502(1-2):132-137, April 2006. 99. D. Li and C.-L. Yang, Acidic electroless copper deposition on aluminum-seeded ABS plastics, Surf. Coat. Technol., 203(23):3559-3568, August 2009. 100. Standard test methods for measuring adhesion by tape test, ASTM Standard ASTM D3359-09, ASTM International, West Conshohocken, PA, 2009. 101. B. Zalba, J.M. Marín, L.F. Cabeza, and H. Mehling, Review on thermal energy storage with phase change: materials, heat transfer analysis and applications, Appl. Therm. Eng., 23(3):251-283, February 2003. 102. M.N.A. Hawlader, M.S. Uddin, and M.M. Khin, Microencapsulated PCM thermal-energy storage system, Applied Energy, 74(l-2):195-202, January-February 2003. 103. R. Yang, Y Zhang, X. Wang, Y. Zhang, and Q. Zhang, Preparation of n-tetradecane-containing microcapsules with different shell materials by phase separation method, Sol. Energ. Mater. Sol. Cells, 93(10): 1817-1822, October 2009. 104. M A . Fetcenko, K. Young, S.R. Ovshinsky, and T. Ouchi, Hydrogen storage alloys having improved cycle life and low temperature operating characteristics, US Patent 7393 500, assigned to Ovonic Battery Company, Inc. (Rochester Hills, MI), July 1,2008. 105. G.T.K. Fey, D.C. Lee, and Y.Y. Lin, High-capacity carbons prepared from acrylonitrile-butadiene-styrene terpolymer for use as an anode material in lithium-ion batteries, /. Power Sources, 119-121:39-44, June 2003. 106. M. Deschamps and R. Yazami, Great reversible capacity of carbon lithium electrode in solid polymer electrolyte, /. Power Sources, 68(2): 236-238, October 1997. 107. Y. Zhang, F. Zhang, G.-D. Li, and J.-S. Chen, Microporous carbon derived from pinecone hull as anode material for lithium secondary batteries, Mater. Lett., 61(30):5209-5212, December 2007. 108. M. Dubois, A. Naji, J.P. Buisson, B. Humbert, E. Grivei, and D. Billaud, Characterisation of carbonaceous materials derived from polyparaphenylene pyrolyzed at low temperature, Carbon, 38(9):1411-1417, 2000. 109. M. Mirzaeian and P.J. Hall, Preparation of controlled porosity carbon aerogels for energy storage in rechargeable lithium oxygen batteries, Electrochim. Acta, 54(28):7444-7451, December 2009. 110. M. Pentimalli, F. Padella, L. Pilloni, E. Imperi, and P. Matricardi, AB5/ABS composite material for hydrogen storage, Int. ]. Hydrogen Energy, 34(10):4592-4596, May 2009. 111. S. Flandrois and B. Simon, Carbon materials for lithium-ion rechargeable batteries, Carbon, 37(2):165-180, February 1999.

Acrylonitrile-Butadiene-Styrene

Polymers

265

112. K.-Y. Chen, S.-H. Wu, Y.-W. Wang, and C.-M. Shu, Runaway reaction and thermal hazards simulation of cumene hydroperoxide by dsc, /. Loss. Prev. Process. Indust., 21(1):101-109, January 2008. 113. K.-H. Hu, C.-S. Kao, and Y.-S. Duh, Studies on the runaway reaction of ABS polymerization process, /. Hazard. Mater., 159(l):25-34, November 2008. 114. C.-S. Kao and Y.-S. Duh, Accident investigation of an ABS plant, /. Loss. Prev. Process. Indust., 15(3):223-232, May 2002. 115. R. Siwek, Determination of technical safety indices and factors influencing hazard evaluation of dusts, /. Loss. Prev. Process. Indust., 9(1): 21-31,1996. 116. J. Brandrup, M. Bittner, G. Menges, and W. Michaeli, eds., Recycling and Recovery of Plastics, Hanser, Munich, 1996. 117. V. Goodship, Introduction to Plastics Recycling, Smithers Rapra, Shrewsbury, 2nd edition, 2007. 118. B.J. Jody, E.J. Daniels, and J.A. Pomykala, Jr., Process for the recovery and separation of plastics, US Patent 6 599 950, assigned to The University of Chicago (Chicago, IL), July 29, 2003. 119. J.E. Gonzales, M.T. Krejchi, R.M. Mafoti, K.W. Odstrcil, F.E. Hoelscher, E.W. Kendall, Y.M. Lee, F.B. Cloud, and A.S. Oriseh, ABS recycling process, US Patent 6 007 005, assigned to Premark RWP Holdings, Inc. (Wilmington, DE), December 28,1999. 120. Y. Koike, Recycled ABS resin, recycled ABS alloy resin and production process of ABS alloy resin, US Patent 6881368, assigned to Canon Kabushiki Kaisha (Tokyo, JP), April 19, 2005. 121. E.J. Daniels, B.J. Jody, and J.A. Pomykala, Jr., Method and apparatus for separating mixed plastics using flotation techniques, US Patent 7 255 233, assigned to UChicago Argonne LLC (Chicago, IL), August 14, 2007. 122. S. Pongstabodee, N. Kunachitpimol, and S. Damronglerd, Combination of three-stage sink-float method and selective flotation technique for separation of mixed post-consumer plastic waste, Waste Manage. (Oxford), 28(3):475-483, 2008. 123. R.D. Pascoe, Investigation of hydrocyclones for the separation of shredded fridge plastics, Waste Manage. (Oxford), 26(10):1126-1132, 2006. 124. R.D. Pascoe, The use of selective depressants for the separation of ABS and HIPS by froth flotation, Miner. Eng., 18(2):233-237, February 2005. 125. R.D. Pascoe, Physical separation of plastics, in R.K. Dhir, M.D. Newlands, and J.E. Halliday, eds., Recycling and Reuse of Waste Materials, pp. 173-188, London, 2003. Thomas Telford. International Symposium 9-11 September 2003, University of Dundee, Scotland.

266

Engineering Thermoplastics:

Polyolefins

and

Styrenics

126. S.-K. Yeh, S. Agarwal, and R.K. Gupta, Wood-plastic composites formulated with virgin and recycled abs, Compos. Sei. TechnoL, 69(13): 2225-2230, October 2009. 127. T. Boronat, V. Segui, M. Peydro, and M. Reig, Influence of temperature and shear rate on the rheology and processability of reprocessed ABS in injection molding process, /. Mater. Process. Techno)., 209(5):27352745, March 2009. 128. A. Palos, N.A. D'Souza, C.T. Snively, and R.F. Reidy, Modification of cement mortar with recycled ABS, Cem. Conor. Res., 31(7):1003-1007, July 2001. 129. A. Arostegui, M. Sarrionandia, J. Aurrekoetxea, and I. Urrutibeascoa, Effect of dissolution-based recycling on the degradation and the mechanical properties of acrylonitrile-butadiene-styrene copolymer, Polym. Degrad. Stab., 91(ll):2768-2774, November 2006. 130. M.-H. Yang, The thermal degradation of acrylonitrile-butadiene-styrene terpolymer under various gas conditions, Polym. Test., 19(1):105110, February 2000. 131. R. Balart, L. Sánchez, J. López, and A. Jiménez, Kinetic analysis of thermal degradation of recycled polycarbonate/acrylonitrile-butadiene-styrene mixtures from waste electric and electronic equipment, Polym. Degrad. Stab., 91(3):527-534, March 2006. 132. J. Bozi, Z. Czégény, and M. Blazsó, Conversion of the volatile thermal decomposition products of polyamide-6,6 and ABS over Y zeolites, Thermochim. Acta, 472(1-2):84-94, June 2008. 133. W.J. Hall and P.T. Williams, Removal of organobromine compounds from the pyrolysis oils of flame retarded plastics using zeolite catalysts, /. Anal. Appl. Pyrolysis, 81(2):139-147, March 2008. 134. T. Bhaskar, K. Murai, T. Matsui, M.A. Brebu, M.A. Uddin, A. Muto, Y. Sakata, and K. Murata, Studies on thermal degradation of acrylonitrile-butadiene-styrene copolymer (ABS-br) containing brominated flame retardant, /. Anal. Appl. Pyrolysis, 70(2):369-381, December 2003. 135. M. Brebu, T. Bhaskar, K. Murai, A. Muto, Y. Sakata, and M.A. Uddin, The effect of PVC and/or PET on thermal degradation of polymer mixtures containing brominated ABS, Fuel, 83(14-15):2021-2028, October 2004. 136. T. Bhaskar, T. Matsui, K. Nitta, M.A. Uddin, A. Muto, and Y. Sakata, Laboratory evaluation of calcium-, iron-, and potassium-based carbon composite sorbents for capture of hydrogen chloride gas, Energy & Fuels, 16(6):1533-1539, November 2002. 137. M. Brebu, T. Bhaskar, K. Murai, A. Muto, Y. Sakata, and M.A. Uddin, Thermal degradation of pe and ps mixed with ABS-Br and debrom-

Acrylonitrïle-Btitadiene-Styrene

Polymers

267

¡nation of pyrolysis oil by fe- and ca-based catalysts, Polym. Degrad. Stab., 84(3):459^67, June 2004. 138. M. Brebu, M. Azhar Uddin, A. Muto, Y Sakata, and C. Vasile, The role of temperature program and catalytic system on the quality of acrylonitrile-butadiene-styrene degradation oil, /. Anal. Appl. Pyrolysis, 63 (l):43-57, March 2002. 139. M. Brebu, T. Bhaskar, K. Murai, A. Muto, Y Sakata, and M.A. Uddin, The individual and cumulative effect of brominated flame retardant and polyvinylchloride (pvc) on thermal degradation of acrylonitrile-butadiene-styrene (ABS) copolymer, Chemosphere, 56(5):433~440, August 2004.

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9 High Impact Poly(styrene) Poly(styrene) (PS) belongs to the largest volume thermoplastic resins (1). Unmodified PS is well suited to applications, where its brittleness is acceptable. In contrast, certain engineering plastics have been used in applications, where less brittleness is required. However, such alternative polymers are often too expensive or they have too superior properties, e.g., other than less brittleness that are not needed for the particular application. For these reasons, a good solution is to start with styrene-based copolymers, and to modify them accordingly (2). Such materials essentially contain PS as the matrix polymer and uniformly dispersed in this matrix are elastomeric types of particles, which form the soft phase (3). The soft phase is essentially composed of poly(butadiene) or of block copolymers of butadiene and styrene. This soft phase can be also addressed as the impact modifier for PS. High impact poly(styrene) (HIPS) is sometimes also accessed as TPS, which stands for toughened PS.

9.1

Monomers

The monomers for HIPS fall into two groups, i.e., the monomers for the matrix resin and the monomers for the soft phase. Monomers are summarized in Table 9.1 and in Figure 9.1. 9.1.1 Impact Modifiers Methyl methacrylate-grafted latex rubber particles has been studied for the impact toughening of PS styrenic matrix polymers. The 269

270

Engineering Thermoplastics: Polyolefins and Styrenics Table 9.1: Monomers for HIPS Remarks/Reference Monomer Styrène α-Methylstyrene 4-Methylstyrene

Matrix resin Matrix resin (4) Matrix resin (4)

Styrène 1,3-Butadiene Methyl methacrylate

Soft phase resin Soft phase resin Soft phase resin

CH3 o 2

Styrène

a-Methylstyrene

p-Methylstyrene

^0-CH3

Methyl methacrylate

Figure 9.1: Monomers used for HIPS addition of these polymers caused a significant increase of the impact strength of the materials. The effectiveness of methacrylate-grafted latex rubbers for HIPS was unexpected because of the poor miscibility properties of these type of polymers (5). The situation is different in the case of acrylonitrile-butadiene-styrene (ABS) types that are miscible with methacrylate-grafted latex rubbers. Nano-powdered styrene/butadiene rubber has been synthesized by the radiation crosslinking of styrene-butadiene rubber (SBR). Trimethylolpropane triacrylate can be used as crosslinking agent. This monomer improves the radiation crosslinking of the SBR latex. Testing of the mechanical properties revealed that the nano-powdered styrene/butadiene rubber is effective in toughening PS (6).

9.2 Polymerization and Fabrication A HIPS can be prepared by blending 15-50 parts of an impact modifier with 85-50 parts of a clear crystalline PS. Such materials are

High Impact Poly(styrene)

271

useful for packaging applications (2). Another method of making HIPS is to first dissolve a rubber in the styrene monomer and then to polymerize the monomer. A styrene monomer containing the dissolved poly(butadiene) rubber is flowed into a polymerization, wherein the styrene monomer is polymerized to form a HIPS (7). 9.2.1

Continuous Radical

Polymerization

HIPS resin with both a high gloss and a high impact strength have been produced using a special in situ polymerization process. A bimodal distribution of the elastomer particles and particular size range and morphology type is maintained (8). A continuous bulk polymerization process with three reaction zones in series has been developed. The degree of polymerization increases from the first reactor to the third reactor. Examples of suitable reactors include continuous stirred tank reactors, stirred tower reactors, axially segregated horizontal reactors, and pipe reactors with static mixers. The continuous stirred tank reactor type is advantageous, because it allows for precise independent control of the residence time in a given reactor by adjusting the level in a given reactor. Thus, the residence time of the polymer mixtures can be independently adjusted and optimized in each of the reactors in series (8). Styrene monomer and a styrene/butadiene copolymer are fed to the first reaction zone. The polymerization is initiated either thermally or chemically. Many chemical initiators are available such as ferf-butyl peroxybenzoate and firf-butyl peracetate. Conditions are established to prevent a phase inversion or the formation of discrete rubber particles in the first reaction zone. The conversion in the first reaction zone should be 5-12%. An important function of the first reaction zone is to provide an opportunity for grafting of the styrene monomer to the elastomer (8). Redox initiators have been proposed. The initiation system is composed from iron sulfate, dibenzoyl peroxide, and a reductant. Of the latter, hydroxyacetone, 2-hydroxy-2-phenylacetophenone, ascorbic palmitate, and toluene sulfinic acid are among the most economical. The reaction conditions are such that the cyclic oxida-

272

Engineering Thermoplastics: Polyolefins and Styrenics

tion and reduction of the metal produces free radicals, which initiate the homogeneous polymerization of the 1,3-butadiene monomer in the presence of styrene monomer (9). Suitable chain transfer agents are ethylbenzene, a-methylstyrene and dodecylmercaptan and most preferred 4-(l-methyl-l-ethylidene)-l-methyl-l-cyclohexene, commonly known as terpinolene. In the second reaction zone, capsule particles are formed with an average size of 0.2-0.6 μ. The particle size of the capsule particles can be controlled by adjusting the temperature, stirring rate, and residence time in the second reaction zone. The conversion in the second reaction zone is 30-40%. The conditions in the third reaction zone are adjusted such that rubber particles formed are predominantly of the cell morphology and have an average particle size of 1.2-8.0 μ. The rate of addition of the poly(butadiene) to the third reaction zone relative to the rate of addition of the styrene/butadiene copolymer to the first reaction zone has a significant impact on the gloss and impact balance of the resultant resin (8). The use of a plasticizer helps to improve the impact strength of the resultant polymer. The plasticizer may be added at any point in the process so as to ensure that it is mixed well with the polymer. Preferred plasticizers include mineral oil, poly(butene)s, or a combination of both mineral oil and poly(butene)s. The amount of plasticizer used is 2 - 4%. 9.2.2

Rubbers

To obtain styrene/butadiene copolymers with a polydispersed PS block, an anionic polymerization was performed. Initiator, termination agent, or coupling agent, respectively, were added in a specific way. At the end of the polymerization reaction, octadecyl 3-(3,5di-ter£-butyl-4-hydroxyl)propionate, and in addition 2,5-di-íerí-butyl-p-cresol are added as antioxidants in order to protect the product during solvent elimination, drying and storage. Morphologies, such as rods, points or capsules can be obtained by tailoring the polydispersity of the poly(styrene) block (10).

High Impact Poly(styrene)

273

The molecular weights of the PS blocks and the polydispersity of the blocks, can be measured according to a standard procedure (11). In a rubber modified styrenic resin the rubber particles are dispersed. The particle size of the dispersed rubber particles has a large influence on the quality of the products. The smaller the particle size of the dispersed rubber particles, the better the gloss of molded articles that is obtained therefrom. The size of the rubber particles is in the range of 1.0-5.0 μ for standard applications. In order to improve the gloss of the fabricated articles, the rubber particles must have a size of less than 1.0 μ. However, with small sized particles, the impact strength is noticeably low. Therefore, it is difficult to improve the gloss, while the impact strength of the molded articles is maintained (4). It has been found that when the rubber particles exhibit a capsule particle morphology, somewhat better results are obtained (3). When the distribution curve of the rubber has two peaks, the impact resistance can be improved, but the appearance of molded articles is poor and particularly the gloss gradient increases. The shape of the distribution curve of the polymer particles can be regulated by changing the molecular weight distribution of the rubbers (4). 9.2.2.1

Vinyl Modifiers

During the polymerization of the styrene, the poly(butadiene) or butadiene copolymer is grafted onto the styrene polymer chain. To increase the grafting efficiency of the poly(butadiene), it is desirable for the poly(butadiene) to have end segments having a high vinyl content rather than eis- or frans-configurations. The vinyl content refers to alkenyl groups configured pendant to the polymer backbone, as opposed to eis- or irans-configurations, which contain the alkenyl groups within the polymer backbone (12). Polymers with high vinyl end segments can be produced by initiating polymerization and allowing the reaction to proceed to near completion. As the polymerization reaction approaches completion, additional monomer and a vinyl modifier are added. The vinyl modifier

274

Engineering Thermoplastics: Polyolefins and Styrenics

H3O—O—CHo

Ό

Figure 9.2: 2,2-Bis(2-oxolanyl)propane (13)

is added to increase the 1,2-addition reaction of the diene monomer in the preparation of the living pre-polymer high vinyl initiator. In other words, the vinyl modifier increases the number of vinyl configured bonds that are formed during polymerization, hence leading to an increased vinyl content. The amount of 1,2-addition product can be increased from about the 5-15% up to 90-100%. 2,2-Bis(2-oxolanyl)propane and other compounds with substituted tetrahydrofuran moieties have been suggested as modifiers (12,13). 2,2-Bis(2-oxolanyl)propane is shown in Figure 9.2. The final segment of the polymer thus has a higher vinyl bond content than the beginning segment. The vinyl concentration of the end segment can be controlled to levels as high as about 70%. However, if both ends of the polymer, or the ends of a star branched polymer should have a high vinyl content and the remaining segments should have a low vinyl content, this method will not work because coupling reactions result in high vinyl in the center of the polymer chain or star branched polymer. To produce linear or branched polymers with all ends having a high vinyl content, an órgano lithium initiator can be used to polymerize a low vinyl middle segment. Subsequently, additional monomer and a vinyl modifier are added to produce ends having a high vinyl content. This method avoids the need for a coupling agent. However, órgano lithium initiators are expensive and unstable. Instead, organic aluminum boron compounds can be used as initiators (12). 9.2.3

Nanocomposites

Nanocomposites composed from HIPS and montmorillonite have

High Impact Poly (styrène)

275

Table 9.2: Properties of a HIPS resin 3 (14) Property Density Melt Mass-Flow Rate (MFR) (200°C/5.0 kg) Tensile Modulus Tensile Stress, yield, Tensile Stress, break, Tensile Elongation, break Flexural Modulus Flexural Strength Notched Izod Impact, -18°C Notched Izod Impact, 23°C CLTE, flow a

Value

Unit

1.04 gem" 3 2.8 g/10min 1650 MPa 19 MPa 24 MPa 52 % 1910 MPa 43 MPa 64 J/m 112 J/m 9.0E--5cm/cm/°C

Styron™ 484, Americas Styrenics LLC

been prepared via the in situ polymerization of styrene in the presence of SBR using an intercalated radical initiator montmorillonite hybrid. The intercalated cationic radical initiator was synthesized from 2,2'-azobis[2-methyl-N-(2-hydroxyethyl) propionamide] by esterification with bromoacetyl bromide, and subsequent quaternization with tributylamine. Sodium montmorillonite was suspended in deionized water. The cationic radical initiator was bound onto the montmorillonite by ion exchange. In contrast, when a bulk polymerization technique is employed, an incomplete exfoliation of the silicate layers in the nanocomposites is observed. The nanocomposites exhibit a significant improvement in their thermal and mechanical properties. About 50% improvement in Young's modulus can be achieved with the addition of 5% of clay (15).

9.3

Properties

In general, the properties of a HIPS type are superior in comparison to a general purpose PS. Properties of a HIPS polymer are shown in Table 9.2.

276

Engineering Thermoplastics: Polyolefins and Styrenics

9.3.1 Mechanical

Properties

In HIPS, desirably the PS is the continuous phase including a discontinuous phase of rubber particles. The size and distribution of the rubber particles in the continuous PS phase can affect the properties of the HIPS. In blends of PS with other materials, the distribution of the noncontinuous phase in the continuous poly(styrene) phase is often similarly important (2). The impact strength of HIPS can go up to sevenfold of that of general purpose PS. The formation of voids in the rubbery phase in HIPS influences its mechanical properties. The formation of voids is believed to facilitate the energy dissipating deformation processes, i.e., crazing and shearing. Crazing and shearing are facilitated under conditions in that the rubber particles can easily cavitate. These conditions can be achieved by avoiding too much crosslinking of the rubber particles, i.e., to keep them more soft. Another possibility is that addition of oils that are acting as nucleation sites for voids (16). The impact strength increases almost linearly with gel content and thus with the degree of crosslinking (17). Figure 9.3 shows the increase of the molecular mobility with the impact strength for ABS. For HIPS it is claimed that the situation is quite similar. The molecular mobility of the soft phase particles is determined by nuclear magnetic-resonance spectroscopy relaxation measurements (16). 9.3.2

Thermal Properties

It has been found that bromine based flame retardants, even when decomposing by different pathways caused by their structure, do not change the decomposition temperature of HIPS. However, antimony trioxide, which is a common Synergist for bromine based flame retardants, reduces the thermal stability of HIPS. This indicates that the Synergist influences the path of the decomposition of HIPS (18). 9.3.3 Particle Size As indicated, the particle size of the rubber is an important factor for both mechanical and optical properties. Transmission electron

High Impact Poly(styrene)

277

1.5 -i 1.4 1.3 ■-—-

>. •¥^ !5 o Ξ 1«

CO 3 Ü

CD O

Έ

1.2 1.1 -

1 0.9 0.8 0.7 6

8

10

12

14

16

2

18

20

Notched Impact Strength /[kJ rrf ] Figure 9.3: Molecular Mobility against Impact Strength (16) microscopy has been found to be a consistent and accurate process for determining the particle size in the resins. Other analytical techniques, such as laser light scattering, employ the use of solvents. However, it has been found that the solvent can cause a swelling of the rubber particles or even dissolve the styrene block copolymer causing inaccuracies in the measurements. The average particle sizes are determined using transmission electron micrographs of ultra-thin slices of the materials. The average size for the particle types are measured separately. Therefore, the cell particles and the single occlusion particles are all treated independently. These particle types have distinctively different appearances, which are recognizable in the transmission electron microscopy image. Particle size measurement is accomplished by (8,19): 1. Overlaying a transparency containing straight lines on a transmission electron microscopy photograph of the resin, 2. Measuring the total length of the line segments contained inside particles of a given type, and

278

Engineering Thermoplastics: Polyolefins and Styrenics Table 9.3: Flame Retardants for HIPS Compund Reference l,2-Bis(pentabromophenyl)ethane l,2-Bis(pentabromophenyl)oxide Decabromodiphenyl oxide Triphenyl phosphate Magnesium hydroxide Nano-modified aluminum trihydrate

(18) (18) (20) (21) (22) (23)

3. Counting the number of particles intersected. This process is repeated for as many lines as is necessary to give a reasonably good statistical average. The average particle size S is obtained from S = ±,

(9.1)

where /{, is the total length of segments bisected and N¡ is the total number of particles intersected.

9.4 Special Additives Basically, HIPS is an impact modified PS. We do not treat this impact modifier as a special additive, since it is not a special additive, but an essential additive. However, sometimes HIPS itself is used as an impact modifier in certain compositions, e.g. of poly(arylene ether)s (24). 9.4.1 Flame Retardants HIPS is used to an extent of more than 75% for television plastics, and 5% for computer plastics (25, p. 580). These fields of applications naturally demand fire proof materials. Some flame retardants for HIPS are summarized in Table 9.3. Most commonly, preliminary information of the effectiveness of a flame retardant is characterized by the UL 94 test (26). There are several varieties of the test, i.e., surface burning, vertical burning, and

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horizontal burning. The test is not intended to reflect the hazards of a material under actual fire conditions. The traditional flame retardant is based on organobromine compounds together with antimony trioxide as a synergist. Magnesium hydroxide is a good flame retardant due to its high decomposition temperature and smoke suppression properties. It is widely used in thermoplastic materials. However, magnesium hydroxide must be added in portions of some 60% to achieve a reasonable effect. In order to rescue the amounts necessary to be added, PS-encapsulated Mg(OH)2 has been prepared. In a high speed mixer Mg(OH)2 was dispersed together with 3-(methacryloxy)propyltrimethoxysilane in acetone solution. After drying, the powder was encapsulated with PS by polymerizing styrene in the mixer. It is believed that the thus modified Mg(OH)2 can be more finely divided in the HIPS matrix an in this way better flame retardancy at lower levels of Mg(OH)2 is achieved (22). Nano-modified aluminum trihydrate show a good synergistic characteristics for improving the flame retardant properties of HIPS, when combined with red phosphorus (23). Recent developments in the field of flame retardants have been reviewed (27). A combination of flame retardants with other properties, such as antioxidants have been developed. An example of such a compound is shown in Figure 9.4.

9.5

Applications

HIPS is a thermoplastic that is widely used in packaging, toys, bottles, housewares, electronic appliances, and light-duty industrial components, because of its good rigidity and ease of coloring and processing. Flame retardant HIPS polymers find application in housings for business machines. Here we present recent issues and examples on applications of HIPS. 9.5.1 Foodservice

Applications

Poly(styrene) tear back lids are commonly used in foodservice applications, in particular as covers for hot cups. It is known that the tearability of a poly(styrene) tear back lid can be improved by

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Engineering Thermoplastics: Polyolefins and Styrenics

&

o

ö

Figure 9.4: Combination of Flame Retardancy with Antioxidant Functionality (27) designing the lid such that the tear back portion is oriented in the direction of extrusion. The manufacturers of PS lids for hot cups have begun to investigate inclusion of filler into the lids to reduce the costs of manufacturing such lids. Historically, PS lids for hot applications have not included a significant amount of filler. Primarily this is due to two reasons. First, PS has traditionally been a low cost raw material and, as such, there was little motivation to include any filler into a formulation. Further, PS used in hot cup lid applications is in general HIPS. HIPS is FDA compliant and exhibits good thermoformability due to its low brittleness. Since a filler is known to increase the brittleness of PS, it was not desired to negate the low brittleness of HIPS with the addition of filler, since this was a property for which HIPS was selected for use in thermoformed hot cup lid applications. However, it has been found that a filler can be added within a specified range to provide a suitably tearable filled thermoformed HIPS container lid when the tear back portion of the lid is oriented in the extrusion direction of the PS, when the tear back lid comprises two sets of tear indentations and a tab portion. In this way, the lid is prepared from a HIPS composition consisting essentially of from 10-15% calcium carbonate as filler (28).

High Impact Poly (styrène) 9.5.2

Refrigerator

281

Cabinets

A typical refrigerator appliance cabinet consists of an outer metal cabinet, an inner plastic liner, typically made from ABS or HIPS, and an insulating polymer foam core, typically a poly(urethane) (PU) foam (29). Blowing agents for the polymer foam are trapped within the cells of the foam. In the past, CFC-11 was usually employed commercially as the blowing agent. According to the Montreal protocol, substitutes for CFC-11 and other hard halógena ted hydrocarbons must be found. Proposed substitutes for CFC-11 are halogenated hydrocarbons that contain at least one hydrogen atom, also known as soft CFCs, which have an ozone depletion potential much less than that of CFC-11. Some of the common blowing agent substitutes currently proposed for insulation-type foams used in refrigeration appliance cabinets are 1,1-dichloro-fluoroethane (HCFC-141 b), 1,1-dichloro2,2,2-trifluoroethane (HCFC-123), and 1,1,1,2-tetrafluoroethane (HFC-134a). While the blowing agents are trapped within the cells of the foam, many different kinds of HCFCs diffuse out from cell walls and contact the inner plastic liner of the refrigerator leading to a chemical attack on the liner, which can cause blistering, catastrophic cracks, crazing, and loss of impact properties, as well as stress whitening or dissolution. Blowing agents, such as HCFC-141b and HCFC-123, appear to be more chemically aggressive than CFC-11 in attacking the inner plastic liner. Several proposals have been made to protect the inner plastic liner from attack by polymer foam blowing agents. The use of a protective polymer film as barrier has been proposed. This barrier consists essentially of a thermoplastic poly(ester) resin, which is a homopolymer or copolymer adduct of an aromatic dicarboxylic acid in an active hydrogen-containing material. However, this poly(ester) resin copolymer has a poor compatibility with styrene resins. Thus, the protective polymer film lacks the desired regrind capability. During the manufacture of appliance cabinets, a thermoplastic synthetic resin sheet, usually made of PS, is either co-extruded with a barrier layer or laminated to a barrier layer to make the inner liner. To successfully recycle the trim or scrap, the protective polymer film

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composition should be compatible with the thermoplastic synthetic resin sheet composition. Other proposed compositions are double layer films, including an inner film containing a copolymer of ethylene vinyl acetate and an outer film containing a copolymer of ethylene and acrylic acid. The purpose of the outer film, however is to improve the adhesion between the PU foam and the outer film. In contrast, the inner film effectively provides a stress relief layer. A polymer composition and a polymer film, which protects thermoplastics from chemical attacks by various polymer foam blowing agents is made of a blend or mixture of polymers and copolymers comprising (29): 1. Apolyolefin, 2. A copolymer derived from monomers comprising a mixture of high density poly(ethylene) (HDPE), a copolymer of ethylene/methacrylic acid, and a synthetic block copolymer rubber such as styrene/butadiene, and 3. A styrenic block copolymer. This polymer film composition can be extruded into a polymer film sheet laminated to or co-extruded with a thermoplastic synthetic resin sheet to make a thermoformable inner liner. The thermoformable inner liner is thermoformed, trimmed, and nested in a spaced relationship within an outer wall element, after which a polymer foam is injected to the space between the inner liner and the outer wall element. 9.5.3 Antistatic

Compositions

Polymer alloys composed of a poly(carbonate) (PC) resin and ABS or HIPS with talc as an inorganic filler have been used for housings or parts for office automation instruments and electrical or electronics instruments. These materials must have high rigidity, thermal stability, flame retardancy, and impact resistance in addition to fluidity ensuring production of large-sized molded articles. For housings of copy machines, antistatic performance is required for preventing dust adhesion. However, an antistatic agent is gen-

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Table 9.4: Examples for Commercially Available HIPS Polymers (14) Tradename

Producer

Remarks

Lubricomp* HIPS

SABIC Innovative Plastics Dow Plastics BASF Americas Styrenics LLC

Various other classes

Opticite™ 540 Polystyrol HIPS Styron™ HIPS

Label Films Various applications

erally hydrophilic in nature, and it is hygroscopic. As methods for imparting antistatic performance to PC composites, antistatic agents including a phosphonium sulfonates, alkali metal sulfonates, are known. A drawback is that phosphonium sulfonate is not very hygroscopic, but it severely lowers the mechanically properties. On the other hand, alkali metal sulfonates exhibit excellent antistatic performance, but they are hygroscopic. However, an excellent antistatic performance is obtained by adding phosphonium sulfonates and phosphate ester that have ether moieties in the organic chain, e.g., a phosphate with polyoxyethylene nonylphenyl ether (30).

9.6

Suppliers and Commercial Grades

Suppliers as well as commercial grades are shown in Table 9.4. An extended list containing some 200 basic types can be found in the internet (14). Tradenames appearing in the references are shown in Table 9.5.

9.7

Safety

9.7.3

Emissions from Processing

In a 2-year study, the emissions produced during the processing of a series of thermoplastic materials were investigated. In the case of HIPS, the emissions at sheet extrusion and injection molding processes were monitored. Sheet extrusion was done at 193°C, whereas, injection molding was done at 225°C.

284

Engineering

Tradename Description

Thermoplastics:

Polyolefins

and

Styrenics

Table 9.5: Tradenames in References Supplier

Antiblaze (Series) Rhodia Inc. Flame retardant (27) Buna® (Series) Bunawerke Hüls GmbH EPDM (2) Chimassorb® 944 Ciba Geigy Hindered amine light stabilizer (CAS 71878-19-8) (27) Cyasorb®1164 Cytec Corp. 4,6-Bis-(2,4-dimethylphenyl)-2-(2,4-dihydroxyphenyl)-s-triazine (27) Dowlex® (Series) Dow LLDPE (24) Escorene® Exxon Ultra low density poly(ethylene) (24) Fyrol® FR-2 Akzo Nobel Tri(l ,3-dichloroisopropy l)phosphate (27) Fyrolflex® RDP Akzo Nobel Tetraphenyl resorcinol diphosphite (27) Hostaflam® Hoechst Ammoniumpolyphosphat (flame retardant) (27) Hostavin® Clariant UV absorber (27) Irgafos® 168 Ciba Specialty Chemicals Tris(2,4-di-ferf-butylphenyl)phosphite (27) Irgastab® FS-042 Ciba hydrogenated tallow amine (27) Lupersol® 331 Arkema, Inc. l,l-Di-(ferf-butylperoxy)cyclohexane (2) Lupersol® 531 Arkema, Inc. l,l-Di-(ierf-amylperoxy)cyclohexane) (2) Lupersol® TAEC Arkema, Inc. 0,0-ferf-Amyl-0(2-ethylbexyl monoperoxy carbonate) (2) Lupersol® TBEC Arkema, Inc. 0,0-ferf-Butyl-0-(2-ethylhexyl)monoperoxy carbonate (2) Lupersol® TBIC Arkema, Inc. 0,0-terf-Butyl-0-isopropyl monoperoxy carbonate (2)

High Impact Poly (styrène)

Table 9.5 (cont): Tradenames in References Tradename Description

Supplier

Melapur® 200 DSM Melamine polyphosphate (27) Melapur® 46 DSM Melamine phosphate (27) Naugard® XL-1 Uniroyal Chemical Co. N,N'-Bis[2-(3-[3,5-di-ferf-butyl-4-hydroxyphenyl]propionyloxy)ethyl]-oxamide (27) PB® 370 FMC Corp. tris[3-Bromo-2,2-bis(bromomethyl)propyl] phosphate (27) Profax® Basell Poly(propylene) (27) Sanduvor® Cytec Hindered amine light stabilizer (27) Saytex® 102E Albemarle Corp. Decabromodiphenyl oxide (27) Saytex® BN-451 Albemarle Corp. Ethylene bis-(dibromo-norbornanedicarboximide) (27) Saytex® BT-93 Albemarle Corp. Ethylene bis-(tetrabromophthalimide) (27) Saytex® RB 100 Albemarle Corp. Tetrabromobisphenol A (27) Styron® 484 Dow Poly(styrene) (27) Taktene® 550 T Lanxess Butadiene rubber (2) Tinuvin® 120 Ciba Specialty Chemicals Corp. 2,4-di-tert-butylphenyl3,5-di-tert-butyl-4-hydroxybenzoate (27) Tinuvin® 234 Ciba 2-(2-hydroxy-3,5-di-a-cumylphenyl)-2H-benzotriazole (27) Tinuvin® 327 Ciba Geigy 2,4-Di-ierf~butyl-6-(5-chloro-2H-benzotriazol-2-yl)phenol, UV absorber (27)

285

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Engineering Thermoplastics: Polyolefins and Styrenics

Table 9.5 (cont): Tradenames in References Tradename Supplier Description Tinuvin® 328 Ciba Geigy 2-(2'-Hydroxy-3',5'-di-ferf-amylphenyl)benzotriazole, UV absorber (27) Tinuvin® 928 Ciba Specialty Chemicals Corp. 2-(2-Hydroxy-3-a-cumyl-5-tert-octylphenyl)-2H-benzotriazole (27) Trigonox® 17 Akzo N-butyl-4,4-di(ferf-butylperoxy)valerate (2) Uvasil® (Series) Enichem Silane based stabilizers (27) Uvasorb® 3V Partecipazioni Industriali S.p.A. UV stabilizers (27) The emission levels generated at the processing of HIPS were estimated from static monitors positioned around the engine. In the monitoring positions stainless steel tubes packed with Tenax® and Chromosorb® as a general purpose adsorbent material were established. After sampling, the adsorbed chemicals were desorbed at 250°C and subsequently analyzed by gas chromatography (GC) coupled with mass spectroscopy (MS). The species that have been detected at sheet extrusion were mostly aromatics, styrene being the most prominent compound. From the injection molding experiments a wider range of volatiles with significantly higher concentrations was measured in comparison to those for the sheet extrusion experiments. In general, in the study, the concentrations of the species detected were found to be in the range 0-2 mg m~3 under standard processing conditions (31). 9.7.2 Emissions from Recycled Products The emission of low molecular weight compounds from recycled HIPS has been investigated using microwave assisted extraction or headspace solid phase microextraction followed by GC/MS (32,33). Styrene was identified already in virgin HIPS, but the amount significantly decreases in reclaimed HIPS. In addition, benzaldehyde, ¿t-methylbenzenaldehyde, and acetophenone were detected in recy-

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Table 9.6: Volatile Compounds in HIPS (32) Volatile Compound Styrene Benzaldehyde Acetophenone 2,4-Diphenylbut-l -ene

Relative Abundance Virgin Recycled 2254 10 6 137

714 11 81

cled HIPS. The presence of oxygenated dérivâtes of styrene can be explained due to oxidation processes of PS. Further, several styrene dimers were found both in virgin and recycled HIPS. These compounds are produced during the polymerization of styrene and stay in the polymeric matrix as the byproducts of polymerization (32). As in the case of styrene, these products decrease in recycled HIPS. Some volatiles are reproduced in Table 9.6. In general, the nature and the relative amount of the emitted compounds increase with higher temperature of exposure and reduced polymeric particle size (33).

9.7.3 Accumulation

in Food from Packaging

General purpose PS and HIPS are used in food packaging applications. In some packaging configurations, with no direct contact of a surface with the polymer the migration of residual styrene monomer via the vapor-phase with subsequent absorption into the food is believed to be a significant mechanism of accumulation. Studies of the migration of styrene monomer from HIPS and likewise from PS foams via the gas phase has been determined in a sealed system. The results show that the amount of styrene migrating from the polymers is proportional to the square root of the time of exposure (34-36). The issues of styrene exposure to the human have been reviewed (37). Styrene has been found to be metabolized to styrene-7,8-oxide by cytochrome P450-IIE1 (38).

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Engineering Thermoplastics: Polyolefins and Styrenics

9.8 Environmental Impact and Recycling A general review on the art and methods of recycling has been given in the literature (25). In addition the history of plastics recycling is presented and the reasons for doing recycling are justified. 9.8.1 Material

Recycling

The recycling of white goods, such as refrigerators involves the shredding of the refrigerators after the removal of the bulk refrigerants. The metallic content of the shredded material is then separated and recycled, and the non-metallic residue is considered as waste, and it is presently land filled. The two dominant plastics in refrigerators are ABS and HIPS. Other plastics may also be present, such as poly(propylene) (PP), poly(ethylene), poly(amide) (PA), and poly(vinyl chloride) (PVC). Many of these plastics can be separated from each other and in addition from HIPS and ABS utilizing differences in density (39). Blends of PC with ABS or ABS/HIPS can be prepared by direct mixing for the reclaimed materials, i.e., blending without the need of sorting before. It has been demonstrated that these mixtures can be easily processed. Furthermore, the mixtures show acceptable mechanical properties (40). 9.8.1.1 Separation by Density Gradient Different grades of both of the ABS and HIPS plastics have specific gravities in the range of 1.055-1.125 g cm" 1 . As a result such mixtures can not be effectively separated by density gradient procedures. The separation of ABS and HIPS using conventional density gradient procedures results in a ABS quality that is about 95% pure. However, a 5% HIPS impurity in the ABS results in a severe breakdown of its properties, in particular of its tensile and impact strengths. This arises because the plastics are not mutually compatible (39). However, it has been demonstrated that the separation of HIPS and ABS is possible by using special solutions. A solution is used with the appropriate density, surface tension, and pH, such as acetic acid and water or hydrochloric acid, salt, surfactant and water.

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The purity of the ABS fraction obtained in this way is greater than 99%. The density of the solution is in the range of 1.055-1.067 g e m - 1 and the p H is adjusted to 1.77-2.05. In turn, HIPS fractions with a high purity can be obtained. The recycled products can be upgraded using commercially available modifiers in order to raise the properties of the recycled material close to those of their virgin counterparts (39). Later, it has been demonstrated that the method of separation can be used in a still more general manner (41). 9.8.1.2 Froth Flotation The method of froth flotation originated from 1906 and was used at this time for the separation of complex mixtures of minerals (42). By using selective wetting agents, froth flotation is a possible separation technique. Acetic acid, methanol and quebracho can be used as selective wetting agents. All of these compounds are potentially selective provided the particle size of the polymers are similar. However, the most promising results are obtained when quebracho at pH 11 is used. A selectivity of separation over a wide particle size range is obtained (43). 9.8.1.3 Hydrocyclone Separation A hydrocyclone system has been proposed for the separation of mixed plastics including among others HIPS. Both water and calcium chloride solutions have been used. A procedure for the determination of the HIPS content in a ABS/HIPS material has been proposed. The analysis method relies on the selective dissolution in K-limonene (44). 9.8.1.4 Triboelectrification The separation by triboelectrification relies on a difference in the dielectric constant of the material to be separated. When nonconductive materials are brought in close contact, a net electric charge is left on the material, either positive of negative, depending on the difference in the dielectric constant of the materials. ABS has a

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Engineering Thermoplastics: Polyolefins and Styrenics

higher dielectric constant than HIPS and would become positively charged (45). Eventually, the charged materials can be separated in a plate condenser. A voltage of maximum 60 kV can be applied across the electrodes. Triboelectric separators for plastics have been described in detail (46,47). The separation efficiency in a triboelectric separator can be enhanced by adding media against which the components of the mixture will charge. As a result, random charging between the components of the mixture is reduced and controlled, and a predictable charging is achieved (47). A media material is a material that will be used to mediate charging. It is chosen such that charging of components of a mixture occurs to best effect separation. In separating mixtures of ABS and HIPS, it was observed that a particular grade of PC caused ABS and HIPS to charge with opposite polarities. This grade of PC is therefore chosen for a media material in the separation of mixtures of ABS and HIPS. To select the media material, the charging properties of the particles of the mixture can be experimentally determined and a material or combination of materials which charges intermediate to the components to be separated is selected (48). In some cases, it may be possible to select a polymer as the media material which is similar or identical to one of the components in the mixture to be separated. For example, if the objective is to recover PA and PC from the other components in a mixture, PA media should be added in quantities sufficient to enable PC to report to the negative electrode, the PA would fall to the center since it would be neutral, and the PVC, polyethylene terephthalate) (PET), PP, HDPE, HIPS and ABS would report to the positive electrode. The remaining components could sequentially be separated by using HIPS, PP, and PVC media. An eight component mixture would be separated using only four separators (47). 9.8.1.5 Upgrading HIPS have been proposed for upgrading of recycled HDPE. In a study, artificially aged HDPE samples were melt blended with HIPS, thereby using an ethylene propylene diene monomer/SBR (49). When in addition the materials are upgraded with phenylenedi-

High Impact Poly(styrene)

291

amine as reactive compatibilizer, the mechanical properties are even better as for the compositions using exclusively virgin HDPE. The method has been proposed for the compatibilization for recycling of municipal plastics wastes. 9.8.2 Feedstock

Recycling

Besides mechanical recycling, the conversion of waste plastics into a petrochemical feedstock is another way for the recovery of the organic materials from a polymer waste. A basic problem is the removal of organobromine compounds. The separation of the organic bromine products from other products of pyrolysis has been attempted by using a special design of pyrolysis reactors with a long residence time (50). The tube reactor is fitted with a distillation column in order to allow to separate the pyrolysis products into four fractions, i.e., heavy oil, middle distillate, light oil, and gases. The experiments revealed that light oil fractions had a very low amount of bromine, whereas the heavy fractions contained much organic bromine. A study concerning the pyrolysis of HIPS and other polymers in the presence of PET has been reported (51). The presence of PET in a mixture of plastics influences significantly the formation of pyrolysis products. The formation of the liquid fraction decreases and the formation of gaseous products increased during the thermal decomposition. A waxy residue is observed in addition to a solid carbon residue. The presence of a calcium hydroxide carbon composite captures the major portion of chlorine and bromine content out from the liquid fraction. In contrast, in the presence of PET, even a combination of calcium a hydroxide carbon composite and an iron oxide carbon composite is not effective to remove halogen the liquid products completely (51). In contrast, an iron oxide carbon composite has been reported that is highly effective in removing both bromine and chlorine from a blend of brominated HIPS and PVC in the course of catalytic thermal degradation, with respect to the liquid fraction of the products of pyrolysis (52). The amounts of chlorine and bromine in the solid have been given. However, a through chlorine balance has not

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Engineering Thermoplastics: Polyolefins and Styrenics

been presented in this study. It is suggested that the halogen free hydrocarbons can be used as a fuel oil or as a feedstock in a refinery. In the carbon and wax residues, antimony compounds have been observed, obviously emerging form the synergistic mixtures of the flame retardants used (51). Material balances for the pyrolysis products from HIPS equipped with flame retardants have been given (53). The pyrolysis experiments were performed to some extent in the presence of zeolite catalysts. The zeolites were added in order to remove organic bromine from the products of pyrolysis. In addition to their potential of destroying toxic brominated flame retardants, zeolites have been believed to be suitable to upgrade the pyrolysis products. The zeolite catalysts are very effective in removing volatile organic bromine. However, they are not very effective in removing antimony bromide from the volatile pyrolysis products. Actually, the zeolites cause a dramatic increase of the formation of hydrogen by a factor of 10. In addition, zeolite catalysts were found to reduce the formation of some valuable pyrolysis products, such as styrene and cumene, but other products, such as naphthalene were formed instead (53).

References 1. H.G. Pohlemann and A. Echte, "Fifty years of polystyrene," in G.A. Stahl, ed., Polymer Science Overview: A Tribute to Herman F. Mark, Vol. 175 of ACS Symposium Series, chapter 18, pp. 265-287. American Chemical Society, Washington, D. C, December 1981. 2. J.M. Sosa, Polystyrene blends and a method of making same, US Patent 7129 297, assigned to Fina Technology, Inc. (Houston, TX), October 31, 2006. 3. A. Echte and H. Gausepohl, Impact-resistant thermoplastic molding material, US Patent 4493922, assigned to BASF Aktiengesellschaft (DE), January 15,1985. 4. T. Ando, M. Iwamoto, M. Kaneko, K. Ichikawa, A. Nakajima, and M. Takaku, Rubber modified styrenic resin composition having high gloss and impact strength, US Patent 5473014, assigned to Mitsui Toatsu Chemicals, Incorporated (Tokyo, JP), December 5,1995. 5. H. Keskkula, D.R. Paul, K.M. McCreedy, and D.E. Henton, Methyl methacrylate grafted rubbers as impact modifiers for styrenic polymers, Polymer, 28(12):2063-2069, November 1987.

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6. D. Li, H. Xia, J. Peng, M. Zhai, G. Wei, J. Li, and J. Qiao, Radiation preparation of nano-powdered styrene-butadiene rubber (SBR) and its toughening effect for polystyrene and high-impact polystyrene, Radiât. Phys. Chem., 76(11-12):1732-1735, November-December 2007. 7. J.M. Sosa and B. Ellis, Process for manufacturing impact resistant monovinylaromatic polymers, US Patent 6569 941, assigned to Fina Technology, Inc. (Houston, TX), May 27,2003. 8. K.E. Bowen and MJ. Hanner, In situ process for making a bimodal HIPS having both high gloss and high impact strength, US Patent 5 985 997, assigned to Chevron Chemical Company (San Ramon, CA), November 16,1999. 9. J. Reimers and J.M. Sosa, Method for polymerizing styrene, US Patent 7087689, assigned to Fina Technology, Inc. (Houston, TX), August 8, 2006. 10. G. Morales-Balado, R. Flores-Flores, A. Montalvo-Robles, R.E. Diaz De Leon-Gomez, and P. Acuna-Vazquez, Preparation of impact-resistant thermoplastic materials on the basis of styrene/butadiene copolymers with polydisperse blocks, US Patent 7608669, assigned to Dynasol Elastomeros, S.A. De C.V. (Altamire (Tamaulipas), MX), October 27, 2009. 11. Standard test method for rubber chemical analysis for polystyrene blocks in SBR (styrene-butadiene rubber) and styrene-reinforced latices, ASTM Standard ASTM D3314-02, ASTM International, West Conshohocken, PA, 2006. 12. J.E. Hall, Insitu removal of chelator from anionic polymerization reactions, US Patent 7 396 887, assigned to Bridgestone Corporation (ChuoKu, Tokyo, JP), July 8,2008. 13. J. Harwood, J. Oziomek, D.F. Lawson, and J.E. Hall, Method of converting anionic living end to protected free radical living end and applications thereof, US Patent 7 279 527, assigned to Bridgestone Corporation (Chuo-Ku, Tokyo, JP), October 9,2007. 14. IDES Integrated Design Engineering Systems, The Plastics Web®, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/prospector/, 2006. 15. P. Uthirakumar, Y.B. Hahn, K.S. Nahm, and Y.-S. Lee, Exfoliated highimpact polystyrene/mmt nanocomposites prepared using anchored cationic radical initiator-mmt hybrid, Ear. Polym. J., 41 (7): 1582-1588, July 2005. 16. F. Ramsteiner, G.E. McKee, and M. Breulmann, Influence of void formation on impact toughness in rubber modified styrenic-polymers, Polymer, 43(22):5995-6003, 2002. 17. G. Cigna, S. Matarrese, and G.F. Biglione, Effect of structure on impact strength of rubber-reinforced polystyrene, /. Appl. Polym. Sei., 20(8):

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and

Styrenics

2285-2295,1976. 18. M. Brebu, E. Jakab, and Y. Sakata, Effect of flame retardants and SD2O3 Synergist on the thermal decomposition of high-impact polystyrene and on its debromination by ammonia treatment, /. Anal. Appl. Pyrolysis, 79(l-2):346-352, May 2007. 19. R.T. DeHoff and F.N. Rhines, eds., Quantitative Microscopy, McGrawHill Series in Materials Science and Engineering, McGraw-Hill, New York, 1968. 20. W.J. Hall, N.M.M. Mitan, T. Bhaskar, A. Muto, Y Sakata, and P.T. Williams, The co-pyrolysis of flame retarded high impact polystyrene and polyolefins, /. Anal. Appl. Pyrolysis, 80(2):406-415, October 2007. 21. A.B. Boscoletto, M. Checchin, L. Milan, P. Pannocchia, M. Tavan, G. Camino, and M.P. Luda, Combustion and fire retardance of poly(2,6-dimethyl-l,4-phenylene ether)-high-impact polystyrene blends. II. Chemical aspects, /. Appl. Polym. Sei., 67(13):2231-2244,1998. 22. S. Chang, T. Xie, and G. Yang, Effects of polystyrene-encapsulated magnesium hydroxide on rheological and flame-retarding properties of HIPS composites, Polym. Degrad. Stab., 91(12):3266-3273, December 2006. 23. G. Chigwada, D. Wang, D.D. Jiang, and C.A. Wilkie, Styrenic nanocomposites prepared using a novel biphenyl-containing modified clay, Polym. Degrad. Stab., 91(4):755-762, April 2006. 24. V.R. Mhetar, R.J. Hossan, and W.E. Pecak, Poly(arylene ether) composition useful in blow molding, US Patent 7 253 227, assigned to General Electric Company (Schenectady, NY), August 7,2007. 25. M.M. Fisher, "Plastics recycling," in A.L. Andrady, ed., Plastics and the Environment, pp. 563-627. John Wiley and Sons, Inc., New York, 2004. 26. Underwriter Laboratories, UL 94: Tests for Flammability of Plastic Materials for Parts in Devices and Appliances, Underwriters Laboratories, Inc., 333 Pfingsten Road, Northbrook, IL, 1.6th edition, 2000. 27. M.V. Troutman, R. Ravichandran, R. Kote, and R.E. King, Flame retarding compounds, US Patent 7531664, assigned to Ciba Specialty Chemicals Corporation (Tarrytown, NY), May 12,2009. 28. J.E. Rush and T. Tran, Filled polystyrene tear back container lids, CA Patent 2 624 734, assigned to Dixie Consumer Products, LLC, September 06,2008. 29. J. Stevens, Protective compositions for reducing chemical attacks on plastics, CA Patent 2172923, assigned to Stevens James, September 30,1996. 30. K. Nagatoshi, Polycarbonate resin composition and moldings thereof, US Patent 7482333, assigned to Idemitsu Kosan Co., Ltd. (Tokyo, JP), January 27,2009.

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31. M.J. Forrest, A.M. Jolly, S.R. Holding, and S.J. Richards, Emissions from processing thermoplastics, The Annals of Occupational Hygiene, 39 (l):35-53, February 1995. 32. F. Vilaplana, A. Ribes-Greus, and S. Karlsson, Analytical strategies for the quality assessment of recycled high-impact polystyrene: A combination of thermal analysis, vibrational spectroscopy, and chromatography, Anal. Chim. Acta, 604(l):18-28, November 2007. 33. F. Vilaplana, M. Martinez-Sanz, A. Ribes-Greus, and S. Karlsson, Emission pattern of semi-volatile organic compounds from recycled styrenic polymers using headspace solid-phase microextraction gas chromatography - mass spectrometry, /. Chromatogr. A, In Press, Accepted Manuscript:-, 2010. 34. P. Murphy, D. MacDonald, and T. Lickly, Styrene migration from general-purpose and high-impact polystyrene into food-simulating solvents, Food Chem. Toxicol., 30(3):225-232, March 1992. 35. K.M. Lehr, G.C. Welsh, C D . Bell, and T.D. Lickly, The vapour-phase migration of styrene from general purpose polystyrene and high impact polystyrene into cooking oil, Food Chem. Toxicol, 31(ll):793-798, November 1993. 36. T.D. Lickly, K.M. Lehr, and G.C. Welsh, Migration of styrene from polystyrene foam food-contact articles, Food Chem. Toxicol, 33(6):475481, June 1995. 37. W. Tang, I. Hemm, and G. Eisenbrand, Estimation of human exposure to styrene and ethylbenzene, Toxicology, 144(l-3):39-50, April 2000. 38. F.P. Guengerich, D.H. Kim, and M. Iwasaki, Role of human cytochrome P-450 IIE1 in the oxidation of many low molecular weight cancer suspects, Chem. Res. Toxicol, 4(2):168-179, March 1991. 39. B.J. Jody, B. Arman, D.E. Karvelas, J.A. Pomykala, Jr., and E.J. Daniels, Method for the separation of high impact polystyrene (HIPS) and acrylonitrile butadiene styrene (ABS) plastics, US Patent 5 653 867, assigned to The University of Chicago (Chicago, IL), August 5,1997. 40. P.A. Tarantili, A.N. Mitsakaki, and M.A. Petoussi, Processing and properties of engineering plastics recycled from waste electrical and electronic equipment (WEEE), Polym. Degrad. Stab., In Press, Accepted Manuscript, 2010. 41. E.J. Daniels, B.J. Jody, and J.A. Pomykala, Jr., Method and apparatus for separating mixed plastics using flotation techniques, US Patent 7 255 233, assigned to UChicago Argonne LLC (Chicago, IL), August 14, 2007. 42. E.B. Kirby, Separating-tank, US Patent 838 626, December 18,1906. 43. R.D. Pascoe, The use of selective depressants for the separation of ABS and HIPS by froth flotation, Miner. Eng., 18(2):233-237, February 2005.

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and

Styrenics

44. R.D. Pascoe, Investigation of hydrocyclones for the separation of shredded fridge plastics, Waste Manage. (Oxford), 26(10):1126-1132, 2006. 45. R.D. Pascoe, Physical separation of plastics, in R.K. Dhir, M.D. Newlands, and J.E. Halliday, eds., Recycling and Reuse of Waste Materials, pp. 173-188, London, 2003. Thomas Telford. International Symposium 9-11 September 2003, University of Dundee, Scotland. 46. R. Köhnlechner, Triboelectric charging and electrostatic separation of diverse, non-conductive mixed waste, especially plastic, employs enclosed vibro-conveyor followed by in-flight separation influenced by non-linear electrostatic field, DE Patent 19 901 743, assigned to Hamos GmbH Recycling und Separ, July 20, 2000. 47. C. Xiao and L. Allen, III., Electrostatic separation enhanced by media addition, US Patent 6452126, assigned to MBA Polymers, Inc. (Richmond, CA), September 17, 2002. 48. L.E. Allen, III and B.L. Riise, Mediating electrostatic separation, US Patent 7063213, assigned to MBA Polymers, Inc. (Richmond, CA), June 20,2006. 49. J. Pospisil, I. Fortelny, D. Michálková, Z. Kruli§, and M. èlouf, Mechanism of reactive compatibilisation of a blend of recycled LDPE/HIPS using an EPDM/SB/aromatic diamine co-additive system, Polym. Degrad. Stab., 90(2):244-249, November 2005. 50. N. Miskolczi, W.J. Hall, A. Angyal, L. Bartha, and P.T. Williams, Production of oil with low organobromine content from the pyrolysis of flame retarded HIPS and ABS plastics, /. Anal. Appl. Pyrolysis, 83(1): 115-123, September 2008. 51. T. Bhaskar, M. Tanabe, A. Muto, and Y. Sakata, Pyrolysis study of a PVDC and HIPS-Br containing mixed waste plastic stream: Effect of the poly(ethylene terephthalate), /. Anal. Appl. Pyrolysis, 77(l):68-74, August 2006. 52. M.A. Uddin, T. Bhaskar, J. Kaneko, A. Muto, Y. Sakata, and T. Matsui, Dehydrohalogenation during pyrolysis of brominated flame retardant containing high impact polystyrene (HIPS-Br) mixed with Polyvinylchloride (PVC), Fuel, 81(14):1819-1825, September 2002. 53. W.J. Hall and P.T. Williams, Removal of organobromine compounds from the pyrolysis oils of flame retarded plastics using zeolite catalysts, /. Anal. Appl. Pyrolysis, 81 (2): 139-147, March 2008.

10 Styrene/Acrylonitrile Polymers Styrene acrylonitrile copolymer (SAN) copolymers have been commercially available since the 1940s. Due to their comparatively high price, initially they have been used in rather special applications. The history of styrenic polymers has been reviewed by various authors (1,2). In a few instances, SAN is also addressed as acrylonitrile/styrene copolymer and abbreviated as AS. However, AS resins may actually target to acrylonitrile-butadiene-styrene resins.

10.1 Monomers Monomers for SAN copolymers are shown in Table 10.1 and in Figure 10.1

10.2 Polymerization and Fabrication SAN copolymers are produced by three processes, the (3): Table 10.1: Monomers for SAN Copolymers Monomer

Remarks

Styrene Acrylonitrile rt-Methylstyrene Divinylbenzene

Basic monomer Basic monomer Instead of styrene Crosslinking agent 297

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Engineering Thermoplastics: Polyolefins and Styrenics

Styrène

Acrylonitrile

a-Methylstyrene

p-Divinylbenzene

Figure 10.1: Monomers used for SAN Copolymers 1. 2. 3. 4. 10.2.3

Emulsion process, Suspension process, Intermediate process, and Continuous mass process. Emulsion

Polymerization

In a conventional emulsion process, the conversion of the monomers to the copolymers reaches 97%. Unreacted monomers in general are problematic with respect to pollution. In particular, unreacted monomeric acrylonitrile (AN) is known to be highly toxic. It has been shown that the conversion can be increased by the addition of certain antioxidants (3). 10.2.2 Intermediate

Polymerization

An intermediate polymerization technique between emulsion polymerization and suspension polymerization has been described. Here, the monomers are first dispersed in water containing a small amount of surfactant and a high molecular weight alcohol to form very small droplets of monomer. The polymerization is effected with a water-soluble free radical initiator, such as potassium peroxydisulfate (4). 30.2.3 Solution and Bulk

Polymerization

For copolymerization of AN and styrene, the composition of polymers is determined by the composition of monomers participating in

Styrene/Acrylonitrile

Polymers

299

Table 10.2: Monomer Reactivity Ratios for Styrene Acrylonitrile (5) Polymerization method Bulk Solution Emulsion Microemulsion

^Streue

0.41 0.34 0.45 1.49

^Acrylonitrile

0.04 0.13 0.02 0.02

the polymerization reaction. Note that AN and styrene polymerize at a different rate. The relation of the instant monomer composition and the composition is given by the copolymerization equation,

v=

d[Mi]

am

=

1 + riw

ïw^·

(1CU)

Here, r\ and Γ2 are the monomer reactivity ratios, m is the molar ratio of the monomer feed, and p is the molar ratio of monomers instantly incorporated into the polymer. It has been found that the monomer reactivities vary by the method of polymerization, even for radical polymerization in different environments, i.e., in bulk, solution and microemulsion (5). The reactivity ratios for different methods of polymerization are given in Table 10.2 The small reactivity ratio for AN indicates that a growing AN radical is reluctant to react with an AN monomer, but rather will react with a styrene monomer. On the other hand, even when a growing styrene radical reacts rather with an AN monomer, the tendency is not as marked. In the limiting case, if both monomer reactivity rations are going to zero, this effects the formation of strictly alternating polymers. The composition of the polymer can be controlled by the ratio of monomers in the monomer feed. In particular, since one of the monomers will be consumed faster that the other in a discontinuous process, the monomer feed can be adjusted accordingly in the course of polymerization. Also in a continuous process, in a cascade of reaction vessels, monomer can be fed into certain stages. For this reason, the monomer mixture initially fed into the reactor varies in composition throughout the reaction in the preparation of the copolymer, and correspondingly, the composition of polymers also changes with conversion. Thus, the SAN copolymer formed

300

Engineering Thermoplastics: Polyolefins and Styrenics

in the course of polymerization becomes a mixture with a distribution of composition. A broad distribution of molecular weight and composition is undesirable, because a broad distribution of the composition of the copolymer resin deteriorates the transparency, the color, and the mechanical property of the articles that are eventually formed (6). Feeding the monomers in different composition in the course of reaction may compensate the change of monomer composition with conversion ratio. In a reactor cascade, a part of the mixture can be fed back into the forgoing reactors, in order to keep the ratio of monomers constant (6). For the control of the molecular weight, mercaptans are used as chain transfer agents. The use of a solvent, such as ethylbenzene or toluene may be helpful for viscosity control of the polymer solution. However, the rate of production may decreased as the load of the devolatizing unit increases. 10.2.4 Expandable

Microspheres

Expandable SAN microspheres are prepared by polymerizing a mixture of styrene and AN with a volatile liquid blowing agent in an encapsulating system. Expandable microspheres of larger size, narrower size distribution and improved expansion characteristics are obtained using an alcohol in the polymerization system, i.e., methanol (7). 10.2.5

Modification

Modified varieties of SAN can be manufactured by grafting, as well as by using varied monomers instead of the basic monomers, i.e., styrene and acrylonitrile. 10.2.5.1 Grafting SAN can be modified, for example by grafting. For example, maleic anhydride (MA) can be grafted onto SAN. This process occurs preferably in a twin-screw extruder by reactive extrusion. An advantage of reactive extrusion is the absence of solvent as the reaction

Styrene/Acrylonitrile

Polymers

301

medium. Because no solvent stripping or recovery is required, product contamination by solvent or solvent impurities is avoided. An extruder reactor is ideally suited for the continuous production of material after equilibrium is established in the extruder barrel for the desired chemical processes. Reactive extrusion has been dealt with in detail elsewhere (8-10). SAN-g-MA is used as compatibilizer in various compositions (11). The reactive functionalized MA groups bound to the polymer can be further allowed to react with reactive stabilizers that are in turn fixed to the polymeric backbone (12). In other words, when the stabilizer is bound to a polymer a better blend obtained when the stabilizer is prevented from migrating out from the polymer. 10.2.5.2

a-Methylstyrene

A variety of SAN consists in the use of a-methylstyrene instead of ordinary styrene (13). The modified copolymer are produced just in the same way as ordinary SAN copolymers. The bulk polymerization effects the special needs to remove the heat of reactions, and moreover, high conversions cannot be reached because the viscosity of the polymer increases drastically with conversion. In order to avoid a high viscosity of the end product before discharging, the mass polymerization is carried out in solution. Ethylbenzene is a common solvent. A serious drawback of solution polymerization is the need to remove the residual solvent. This problem is also present in emulsion polymerization techniques, where the water must be removed and moreover cleaned. An alternative to remove the residual solvent or monomer, respectively is the extraction by supercritical carbon dioxide. In addition, the polymerization itself can be performed in subcritical carbon dioxide as solvent. Not that the critical point of carbon dioxide is at 37°C and 73 bar. Advantageously, the monomer feed is adjusted to the azeotropic point of the pair of monomers, so that the polymer has the same composition as the monomer. Azeotropic points are shown in Table 10.3.

302

Engineering Thermoplastics: Polyolefins and Styrenics Table 10.3: Azeotropic points Monomer 1

Monomer 2

Styrene Methyl methacrylate Styrene Acrylonitrile «-Methylstyrene Acrylonitrile a With respect to monomer 1

Azeotropea/[%] 75 67.1

Actually, most SAN types have a composition near the azeotropic point, just for the reasons explained above. 10.2.6 Interfering

Reactions

10.2.6.1 Popcorn Polymers Usually, popcorn polymers are formed in the radical polymerization of monomers containing small amounts of crosslinkers. However, the polymerization of SAN is a remarkable exception (14). Popcorn polymers are hard, brittle, highly crosslinked porous masses, named as such because of their physical appearance. The formation of popcorn polymers in industrial polymerization processes is highly undesirable. The formation can be suppressed by suitable crosslinking inhibitors. However, in order to avoid the formation on the walls of a reactor that are mainly in contact with the gas phase, volatile crosslinking inhibitors must be chosen. Examples for volatile crosslinking inhibitors are nitric oxide and sulfur dioxide (15,16). 10.2.6.2 Yellowing SAN polymers have a natural tendency to assume a yellowish cast when conventionally manufactured (17). This arises from the residual oxygen in the monomer feed. However, when the level of oxygen is below 2 ppm then this problem can be controlled.

10.3 Properties Properties of a SAN resin are shown in Table 10.4. SAN polymers are appreciated because of their excellent transparency and good

Styrene/Acrylonitrile

Polymers

303

Table 10.4: Properties of a SAN resin a (18) Property

Value

Density Water absorption (saturation) Water absorption (equilibrium) Melt Mass-Flow Rate (MFR) (220°C/10.0 kg) Melt Mass-Flow Rate (MFR) (230°C/3.8 kg) Melt volume-flow rate (220°C/10.0 kg) Tensile Modulus Tensile Stress, yield, Tensile Stress, break, Flexural Strength Charpy Unnotched Impact Strength (23°C) Charpy Unnotched Impact Strength (—30°C) Charpy Unnotched Impact Strength (23°C) Unnotched Izod Impact Strength (23°C) Specific Heat Electric Strength Surface Resistivity Volume Resistivity a

Unit

1.08 gem3 0.2 % /o 0.5 13 g/10min 5.0 g/10min 16.0 cm 3 /10min MPa 3600 MPa 65 MPa 68 MPa 95 15 klm" 2 17.0 kjnr2 16.0 kjm~ 2 12.0 kjrrr 2 1380 kJkg^K" 1 9.1 kVmrrT 1 1.0Ε+15Ω 1.0E+13Qcm

Tyril® 905, DOW

resistance to chemicals. SAN types with a high content of AN are known as barrier polymers since they exhibit a low permeability to gases. The properties of SAN types can be found in more detail in the technical information brochures provided from the manufacturers, e.g., in (19). 30.3.1 Mechanical

Properties

SAN polymers exhibit high stiffness, dimensional stability and resistance to fluctuating temperatures. 30.3.2

Thermal Properties

The glass transition temperatures are nearly linearly dependent on the mol fraction of, e.g., styrene in the copolymer, as shown in Figure 10.2.

304

Engineering Thermoplastics: Polyolefins and Styrenics

50

55

60

65 70 75 80 Amount Styrene /[mol-%]

85

90

Figure 10.2: Glass Transition Temperatures viz. Composition (20) The data agree well with theoretical data obtained from the Barton equation (21). For copolymers and specifically for the styrene/AN system, the glass transition temperature is dependent on the amounts of the dyads SS,AS,AA occurring in the a copolymer, where S denotes a styrene monomer and A denotes a acrylonitrile monomer, as (22) Tg = FssTg,sS + FsATg,SA + FAATg,AA

■

(10.2)

Tg,ss and Tg,AA ai*e the glass transition temperatures of the respective homopolymers. 10.3.3 Electrical Properties SAN exhibits good electrical properties. 10.3.4

Optical Properties

Some SAN types combine excellent transparency with chemical resistance, which is not the case for e.g., poly(methyl methacrylate) (PMMA). This property make these types useful for household applications, such as mixers, as well as decorative containers for otherwise aggressive media. The optical transparency against wavelength is shown in Figure 10.3

Styrene/Acrylonitrile

Polymers

305

uu 90 -

//Γ~~

80 c g "w

70 -

E

(Il

60 -

l / /

to

05

C CO

Glass

/ /

50 -

'

Luran® Crystal Clear

40 30 200

1

1

1

i

1

1

1

300

400

500

600

700

800

900

Wavelength/[nm]

Figure 10.3: Optical Transparency of Glass in Comparison to SAN Types (23)

10.3.5 Chemical

Resistance

Data about the chemical resistance of styrene polymers in general have been compiled (24). A few data concerning SAN polymers are collected in Table 10.5. Table 10.5: Chemical Resistance of Luran® (24) Substance Acetic acid (100 %) Benzene Diethylhexyl phthalate Hexane

20°C

50°C

+ 0

0 0

+: Resistant over a prolonged period 0: Limited resistance: -: not resistant

Substance Bromine (1) Ethyl acetate Aniline THF

20°C

50°C

-

-

306

Engineering Thermoplastics: Polyolefins and Styrenics

10.4 Special Additives In thermoplastic compositions containing SAN various additives that are ordinarily incorporated in such resin compositions may be added. These include (25): • • • • • • • • • •

Fillers or reinforcing agents, Antioxidants, UV absorbers, y-radiation stabilizers, Flame retardants, Plasticizers, Antistatic agents, Colorants, Lubricants, and Mold release agents.

The individual additives have been discussed exhaustedly and exemplarily (25).

10.5

Applications

Typical applications of SAN include • • • • • • 10.5.1

Automotive applications, Electrical and electronic applications, Household goods, Containers, Medical applications, and Cosmetics, Blends

10.5.1.1 Blends with Poly(carbonate)s (PC)s The transparency of PCs makes them useful in a variety of applications. However, the processing characteristics of PCs and their physical properties in the finished products make it desirable to

Styrene/Acrylonitrile

Polymers

307

Table 10.6: Refractive Indices of Some Polymers (25) Polymer

Refractive index

Poly(carbonate) Poly(styrene) Poly(acrylonitrile) Poly(methyl methacrylate) Poly(dimethylsiloxane)

1.58 1.59 1.52 1.49 1.40

blend PCs with other polymeric materials such as a SAN. This effects an improvement of flow and processability. However, even at relatively low SAN levels, the blends can become hazy or opaque. Transparent compositions can be obtained by using a poly(siloxane)/PC copolymer instead of pure PC (25). Thin-walled articles can be successfully fabricated from such a composition. The SAN should not contain more than 25% of AN. It is believed that the transparency of the poly(siloxane)/PC copolymer is related to the size and the distribution of the siloxane units within the copolymer. The distribution may be controlled by the method of preparation. Transparent poly(siloxane)/PC copolymers can be produced by first reacting a carbonate oligomer with siloxane bischloroformate to produce an intermediate that is subsequently reacted with a biphenol, phosgene, and an endcapping reagent (26). This method produces better transparency than methods wherein the phosgene, the biphenol and the siloxane are simultaneously present. It is believed that producing the bischloroformate before adding phosgene helps to make a more randomly distributed copolymer due to reactivity differences between siloxanes and biphenols versus phosgene. Further, methods using phase transfer catalysts are suitable for the production of transparent poly(siloxane)/PC copolymers (27). As phase transfer catalyst a methyltributyl ammonium salt is used. It is surprising that poly(siloxane)/PC copolymer and SAN can form a transparent blend because the refractive index of poly(dimethyl siloxane) (PDMS) is around 1.4, which is very different from that of SAN (25). Moreover, PDMS can form a transparent blend with SAN that would not form a transparent blend with PC. Refractive indices of some polymers are summarized in Table 10.6.

308

Engineering Thermoplastics: Polyolefins and Styrenics άΐ> -

30 -

\

25 -

Λ

Q

x *

\

20 C Φ

SAN, 17 % CFC, 0.5 % TEG SAN, 19%CFC SAN, 1 7 % CFC

15 -

\ * K

10 5 -

0

1

Λ.

x ■ * V^-^ X

I

1

. +

*

I

2

I

3

*

■■-■i-

4

I

5

r

6

i

7

Expansion time/[min] Figure 10.4: Blowing Efficiency of Various Formulations (28)

8

10.5.2 Expandable Resins Expandable polymeric blends with SAN are conventionally manufactured by incorporating a blowing agent, such as chlorofluorocarbons. Some of these blowing agents are known to be environmental pollutants. It has been found that the incorporation of a small amount of triethylene glycol in expandable SAN beads provides equivalent or better expansion. On the other hand, the reaction is more rapid and less conventional blowing agent is needed. In Figure 10.4, the blowing efficiency of various formulations containing conventional blowing agent trichlorofluoromethane (CFC) and triethylene glycol is shown. The samples are expanded in a rotating steam chamber for a predetermined time (28). After annealing, the density becomes still smaller. 30.5.3

Low Gloss

Additives

Thermoplastics having a low gloss finish are useful in the manufacture of articles and components for a wide range of applications,

Styrène/Acrylonitrile

Polymers

309

from automobile components, to decorative articles, to housings for electronic appliances, such as computers. A low gloss finish for a plastic article can be obtained using different methods. Mechanically texturing a plastic surface has long been used, but this type of surface finish is prone to wear and ultimately increases in gloss with use. Further, mechanical texturing adds processing steps and increases manufacturing costs. Modifications of the moldable thermoplastic composition itself are therefore desirable (29). Low gloss additives have been described, such as epoxy resins. In addition, SAN copolymers are specifically useful. Suitable SAN copolymers have 75% styrene content. The low gloss additive gel is melt blended, with another resin, e.g., PC. As usual, certain additives can be added to the composition. Among others, the use of an anti-drip agent has been proposed, namely poly(tetrafluoroethylene) (PTFE)). The anti-drip agent may be encapsulated by a rigid copolymer, for example, SAN, which is known as teflon encapsualed in SAN (TSAN) (29). Encapsulated fluoropolymers can be made by polymerizing the encapsulating polymer in the presence of the fluoropolymer, for example in an aqueous dispersion. TSAN may provide significant advantages over PTFE, in that TSAN may be more readily dispersed in the composition. A suitable TSAN may is composed from 50% PTFE and 50% SAN (29).

10.5.4

Laser-inscribed

Moldings

The production of laser-inscribed moldings from PMMA has been considered to be impossible in satisfactory quality without the addition of additives to increase the absorption coefficients of the laser radiation employed. However, blends based on PMMA and related acrylics have been described (30). Transparent molded articles having a high contrast laser inscription thereon are produced from a polymer mixture consisting of methacrylic esters, SAN, and rubber particles.

330

Engineering Thermoplastics: Polyolefins and Styrenics

Table 10.7: Examples for Commercially Available SAN Polymers Tradename

Producer

Blendex SAN Lastil SAN SAN Luran® SAN TYRIL™ SAN

Chemtura LATI S.p.A. SABIC Innovative Plastics Asia Pacifie BASF Corporation Dow Plastics

10.6 Suppliers and Commercial Grades Suppliers as well as commercial grades are shown in Table 10.7. A more detailed list can be found in the internet (31). Glass fiber reinforced types are known for a long time and are commercially available (32). Tradenames appearing in the references are shown in Table 10.8.

10.7 Environmental Impact and Recycling Recycling of SAN was simulated at reprocessing by repeated injection molding up to five cycles. The chemical nature of SAN was obviously unchanged after reprocessing. However, at reprocessing, the molecular weight decreased slightly. In addition, SAN became progressively yellow with increasing cycles, however, its most important mechanical properties remained unchanged (33).

Styrène/Acrylonitrile

Polymers

Table 10.8: Tradenames in References Tradename Description

Supplier

Cyasorb® 531 Cytec Corp. 2-Hydroxy-4-n-octyloxybenzophenone(29) Cyasorb® 5411 Cytec Corp. 2-(2H-Benzotriazol-2-yl)-4-(l ,1 ,3,3-tetramethylbutyl)-phenol (29) Cyasorb® UV-3638 Cytec Corp. 2,2'-(l,4-phenylene)bis(4H-3,l-benzoxazin-4-one(29) Irgastat™ P18 Ciba Poly(ether-b-amide (antistatic agent) (29) Lexan® General Electric Poly(carbonate) (27) Lucalen® A 3110 MX BASF AG polyethylene/acrylic acid/acrylate (12) Lucryl® BASF AG Methacrylate copolymer (30) Lupolen® (Series) BASF AG Poly(ethylene) (12) Panipol® EB Panipol Oy Poly(aniline) (25,29) Pelestat® (Series) Sanyo Chemical Industries Poly(ether amide) (antistatic agent) (29) Printex® Evonik Degussa Carbon black (30) Ultramid® (Series) BASF AG Poly(amide) (12) Uvinul® 3030 BASF AG l,3-Bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3diphenyl-acryloyl)oxy]methyl]propane (UV absorber) (29)

311

332

Engineering Thermoplastics:

Polyolefins

and

Styrentcs

References 1. H.G. Pohlemann and A. Echte, "Fifty years of polystyrene," in G.A. Stahl, ed., Polymer Science Overview: A Tribute to Herman F. Mark, Vol. 175 of ACS Symposium Series, chapter 18, pp. 265-287. American Chemical Society, Washington, D. C , December 1981. 2. L.A. Utracki, History of commercial polymer alloys and blends (from a perspective of the patent literature), Polymer Engineering & Science, 35(1):2-17, January 1995. 3. J.W. Gowan, Jr. and C.G. Force, Method for copolymerization of styrene and acrylonitrile, US Patent 4517347, assigned to Westvaco Corporation (New York, NY), May 14,1985. 4. D.C. Curfman and G.D. Rea, Process for polymerization of styrene and acrylonitrile, US Patent 4182820, assigned to Borg-Warner Corporation (Chicago, IL), January 8,1980. 5. P.G. Sanghvi, A.C. Patel, K.S. Gopalkrishnan, and S. Devi, Reactivity ratios and sequence distribution of styrene-acrylonitrile copolymers synthesized in microemulsion medium, Eur. Polym. /., 36(10):22752283, October 2000. 6. H.S. Lee and Y.C. Jang, Process for preparing acrylonitrile-styrene copolymer, US Patent 6 488 898, assigned to LG Chemical Ltd. (Seoul, KR), December 3, 2002. 7. J.L. Garner, Polymerization of styrene acrylonitrile expandable microspheres, US Patent 3 945 956, assigned to The Dow Chemical Company (Midland, MI), March 23,1976. 8. M. Xanthos, ed., Reactive extrusion: Principles and practice, Vol. 1 of Polymer Processing Institute booL·, Hanser, Munich, 1992. 9. W.D. Richards, G.R. Bradtke, R.H. Wildi, L.M. Gemmell, J.A. Hill, V.K. Berry, C.M.M. Pottier-Metz, J.R. Campbell, J.L. Little, and K.G. Powell, Dispersive reactive extrusion of polymer gels, US Patent 5 770 652, June 23,1998. 10. R.J. Kumpf, J.S. Wiggins, and H. Pielartzik, Reactive processing of engineering thermoplastics, Trends Polym. Set., 3(4):132-138, April 1995. 11. H.-J. You, C.-H. Lee, B.-I. Kang, and S.-L. Kim, Thermoplastic resin composition and method for preparing thereof, US Patent 7345112, assigned to LG Chem, Ltd. (KR), March 18, 2008. 12. R. Pfaendner, H. Herbst, K. Hoffmann, S. Evans, and A. Steinmann, Functionalised polymers, US Patent 7 300 978, assigned to Ciba Specialty Chemicals Corporation (Tarrytown, NY), November 27,2007. 13. R.C. Leiberich, R. Dohrn, H.C. Waldmann, and H. Alberts, Preparation of alpha-san copolymers from alpha-methyl styrene and acrylonitrile, DE Patent 19618832, assigned to Bayer AG, November 13,1997.

Styrène/Acrylonitrile

Polymers

313

14. J.W. Breitenbach and H. Sulek, Popcornpolymerbildung in nicht-vernetzenden Systemen, Mh. Chent., 98(5):1767-1771, September 1967. 15. S.M. Campbell and C.-Y. Sue, Nitric oxide for vapor phase elimination of styrène and acrylonitrile popcorn polymer in bulk SAN production, US Patent 5272231, assigned to General Electric Company (Pittsfield, MA), December 21,1993. 16. J.C. Wozny, C.-Y. Sue, and J.E. Pace, Sulfur dioxide for vapor phase elimination of styrene and acrylonitrile popcorn polymer in bulk SAN production, US Patent 5 399 644, assigned to General Electric Company (Pittsfield, MA), March 21,1995. 17. R.W. Kent, Jr., Process for the preparation of styrene and acrylonitrile containing polymers, US Patent 4 243 781, assigned to The Dow Chemical Company (Midland, MI), January 6,1981. 18. IDES Integrated Design Engineering Systems, The Plastics Web®, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/prospector/, 2006. 19. Anonymous, Luran (SAN) - properties, processing, general information, Brochure KSIL 0701 BE, BASF Aktiengesellschaft, Ludwigshafen, Germany, 2007. [electronic:] http://www.plasticsportal.net/wa/plasticsEU~en_GB/ function/conversions:/publish/common/upload/general_purpose_ styrenics/Luran_Brochure.pdf. 20. K.C. Lee, L.M. Gan, C.H. Chew, and S.C. Ng, Copolymerization of styrene and acrylonitrile in ternary oil-in-water microemulsions, Polymer, 36(19):3719-3725,1995. 21. H. Suzuki and V.B.F. Mathot, An insight into the Barton equation for copolymer glass transition, Macromolecules, 22(3):1380-1384, March 1989. 22. J.M. Barton, Relation of glass transition temperature to molecular structure of addition copolymers, /. Macromol. Sei., Polym. Symp., 30 (l):573-597,1970. 23. Anonymous, Luran crystal clear (SAN) - for a high-end look and outstanding transparency, Flyer KSEL 0603 FE, BASF Aktiengesellschaft, Ludwigshafen, Germany, 2006. [electronic:] http://www.plasticsportal.net/wa/plasticsEU~en_GB/ function/conversions:/publish/common/upload/general_purpose_ styrenics/Luran_Crystal_Clear__Flyer.pdf. 24. Anonymous, Chemical resistance of styrene copolymers, Brochure KTCI 9900 e 05.2002, BASF Aktiengesellschaft, Ludwigshafen, Germany, 2007. [electronic:] http://www.plasticsportal.net/wa/plasticsEU~en_GB/ function/conversions:/publish/common/upload/general_purpose_ styrenics/Chemical_Resistance_Styrene_Copolymers.pdf.

314

Engineering

Thermoplastics:

Polyolefins

and

Styrentcs

25. K. Glasgow and N. Alle, Transparent polymeric compositions comprising polysiloxane-polycarbonate copolymer, articles made therefrom and methods of making same, US Patent 7432327, assigned to SABIC Innovative Plastics IP B.V. (Bergen op Zoom, NL), October 7, 2008. 26. J.M. Silva, D.M. Dardaris, and G.C. Davis, Method of preparing transparent silicone-containing copolycarbonates, US Patent 6 833 422, assigned to General Electric Company (Niskayuna, NY), December 21, 2004. 27. P.D. Phelps, E.P Boden, G.C. Davis, D.R. Joyce, and J.F. Hoover, Silicone-polycarbonate block copolymers and polycarbonate blends having reduced haze, and method for making, US Patent 5530083, assigned to General Electric Company (Schenectady, NY), June 25,1996. 28. M.H. Tusim and T.W. Rhoads, Plasticizers for expandable styreneacrylonitrile resin, US Patent 5 071606, assigned to The Dow Chemical Company (Midland, MI), December 10,1991. 29. J. Chen, T. Hoeks, and X. Yang, Low gloss thermoplastic composition, method of making, and articles formed therefrom, US Patent 7 563 846, assigned to Sabic Innovative Plastics IP B.V. (NL), July 21,2009. 30. G.E. Mc Kee, M. Welz, A. Deckers, D. Wagner, P.O. Damm, and H.-J. Oslowski, Use of mixtures of polymethyl methacrylate and styrene-acrylonitrile copolymers for the production of laser-inscribed moldings, US Patent 6020106, assigned to BASF Aktiengesellschaft (Ludwigshafen, DE), February 1, 2000. 31. IDES Integrated Design Engineering Systems, Styrene acrylonitrile (SAN) resins, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/generics/SAN/SAN_products.htm, 2008. 32. M. Färber and H.A. Petersen, Reinforced styrene-acrylonitrile polymers, US Patent 3 951906, assigned to Uniroyal Inc. (New York, NY), April 20,1976. 33. S. Bastida, C. Marieta, J.I. Eguiazábal, and J. Nazábal, Effects of reprocessing on the nature and properties of SAN, Eur. Polym.}., 31(7):643646, July 1995.

11 Methyl methacrylate/ Butadiene/Styrene Polymers Methyl methacrylate-butadiene-styrene (MMBS) types are rarely used as such, but rather in blends as impact modifiers (1). Styrenic copolymers such as acrylonitrile-butadiene-styrene (ABS) and MMBS make up the largest category of impact modifiers, with about 45% of the impact modifier market (2). The field of polymer blends and the reasons for the addition of impact modifiers have been reviewed (3). Core-shell emulsion polymers with a core or rubbery stage based on homopolymers or copolymers of butadiene are used as impact modifiers in matrix polymers, such as ABS, for styrene acrylonitrile copolymer methyl methacrylate (MMA) polymers, poly(vinyl chloride) (PVC), and in various engineering resins such as polycarbonate) (PC) poly(ester)s, or poly(styrene)s, further in thermosetting resins such as epoxies. Such impact modifiers containing copolymers of butadiene and styrene and at least one stage or shell of poly(methyl methacrylate) are known MMBS core-shell polymers.

11.1

Monomers

Monomers for ABS polymers are shown in Table 11.1 and in Figure 11.1. 315

316

Engineering Thermoplastics: Polyolefins and Styrenics Table 11.1: Monomers for MMBS Monomer

Remarks

1,3-Butadiene Styrène Methyl methacrylate Butylène dimethacrylate Divinylbenzene

Core Core/shell

Butadiene

Crosslinking agent Crosslinking agent

Styrene

Methyl methacrylate

Figure 11.1: Monomers used for MMBS

11.2 Polymerization and Fabrication MMBS are core-shell copolymers that are prepared in two stages. The core is a copolymer of 50-90% of 1,3-butadiene and the rest is preferably styrene or additional monomers such as acrylonitrile, methacrylates, and olefins (4). MMBS has been used in blends for PVC already in the 1960s. It is prepared from a butadiene/styrene latex be emulsion polymerization (5). A high content of butadiene of more than 50% is desirable. For the second step, the ratio of styrene to MMA should be 45-25%. If the percentage of styrene is below 50%, no pronounced effect in the improvement of the impact strength of the final blend is obtained (5). High rubber levels are desired and such levels have been reached by only coagulation procedures. Using coagulation techniques, rubber contents of greater than 70% were not reached (5). 11.2.1 Basic Method for Preparation Subsequently, a method for the preparation of a MMBS copolymer is described in detail. The preparation consists in the (6):

Methyl methacrylate/Butadiene/Styrene

Polymers

317

1. Preparation of the rubber latex, 2. Grafting the rubber latex, and 3. Isolation of the final polymer. 11.2.1.1 Rubber Latex In the first step a rubbery polymer latex is prepared by emulsion polymerization of styrene and butadiene, the styrene being in an amount of 25%. Divinylbenzene is added as crosslinking agent in an amount of 1%. Diphenyl oxide sulfonate is used as emulsifier in aqueous solution and sodium formaldehyde sulfoxylate acts as a buffer in order to reach a pH of 4. As radical initiator, cumene hydroperoxide is used and the polymerization is conducted 70°C for 9 h. The end of the reaction period is detected as no further pressure drop is observed due to the consumption of butadiene. 11.2.3.2

Graft Polymer

To the latex prepared, 7% of styrene are added followed by sodium formaldehyde sulfoxylate dissolved in water and cumene hydroperoxide. An exothermal reaction is observed. One hour after the completion of the exotherm, 7% of methyl methacrylate, 0.07% of butylène dimethacrylate, 0.07% parts sodium formaldehyde sulfoxylate dissolved in water and 0.15% of cumene hydroperoxide are added and the reaction is allowed to completion. The resultant polymer latex has a butadiene/styrene rubber content of 77.5% by weight, with an overall butadiene content of 73.6%. 11.2.1.3 Isolation of the Graft Polymer The isolation of the latex prepared as described before occurs in a spray dryer by atomization in the presence of air as the drying medium. Fumed silica is added by suspending it in the gaseous drying medium. The silica acts as anti-caking agent, or drying aid. Polymer powders of particularly high storage stability are then obtained. The finer the particles of the anti-caking agents are, the less is the quantity necessary for stabilization (7). Aluminum silicate or stéarate coated calcium carbonate may serve as other anti-caking agents (8).

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11.2.2 Varied Methods Several procedures have been disclosed that claim to be an improvement of the basic method of preparation. For most commercial uses, it is desirable to have the emulsion particle size above 100 nm, preferably near 200 nm, for the optimization of the impact strength performance in the various matrix polymers. There are deficiencies with both of the conventional processes from the viewpoint of manufacturing, as the enlargement, i.e., the process is a slow process, whereas the agglomerative process usually involves the dilution in emulsion polymer solids and is thus a less efficient process in terms production rate. Another problem is the formation of butadiene dimer, i.e., 4-vinylcyclohex-1-ene and others. These useless volatiles must be vented at an intermediate stage in the process, which slows down the process. Agglomeration may be accomplished in several ways, such as by controlled adjustment of solids, by extensive shear of the emulsion, or by carefully controlled addition of electrolytes, such as water-soluble salts of inorganic acids, e.g., sodium chloride, potassium hypophosphite, potassium chloride, or sodium phosphate. Improved processes rely on the method of addition of the monomers in the distinct stages of polymerization (9). Even when this process substantially reduces polymerization time, in latex core-shell polymer emulsions with a weight fraction of greater than 70% of butadiene, slurries with an undesirably great particle size greater are obtained, when coagulated at temperatures greater than 20°C. Namely, the slurry particle size increases with increasing temperature. On the other hand, when coagulating below about 20°C, the use of efficient cooling processes is mandatory. However, when in the process of polymerization additional stages are added, smaller particle sizes can be obtained by coagulation even at temperatures above 20°C (10).

11.3 Properties Selected properties of a MMBS type are shown in Table 11.2.

Methyl methacrylate/Butadiene/Styrene

Polymers

319

Table 11.2: Properties of an MMBS Polymer a (11) Property

Value

Density Water absorption (saturation 23°C) 0 Tensile Modulus Tensile Strength, yield, 23°C Tensile Strain, yield 23°C Nominal Strain at break Charpy Notched Impact Strength, 23°C Vicat softening temperature CLTE, flow (TMA) Surface Resistivity Volume Resistivity Limiting oxygen index a Cyrolite® G-20 H1FLO, Evonik Röhm

11.3.1

Unit

1.11 g/cm 3 .30 % 2300 MPa 51 MPa 3.4 % 11 % 11 kj/m 2 95 °C 9E-5 cm/cm/°C 1.0E+13ohms 1.0E+13ohmm 18 %

Thermal Properties

MMBS modifiers a have poor resistance to thermal oxidative degradation. This poor resistance may manifest itself most strongly during such procedures as isolation and oven drying. The least severe manifestation is slight discoloration, while dryer fires are an extreme, though not uncommon, consequence of failure to stabilize MMBS modifiers (12). 11.3.2

Optical

Properties

Aqueous-based MMBS impact modifiers are useful in applications where the optical properties, i.e., clarity of the modified resin is important (13).

11.4 Special Additives Antioxidants are incorporated into the MMBS modifiers to reduce the risk of discoloration (12). Preferred antioxidants are phenolic compounds. An accelerated stability test to monitor the rate of color development in MMBS resins under heat aging conditions in an oxygen deficient environment has been described (12). In plaque form, the

320

Engineering Thermoplastics: Polyolefins and Styrenics

MMBS is much less accessible to oxygen than as a powder so that mild oxidative discoloration can be conveniently monitored at 170°C in a time frame of maximum 5 h. A sample of milled sheet is positioned between two Mylar® films and pressed. Then the films are removed, and the plaque is cut into rectangles, which are placed in a forced air oven. Samples are periodically removed and rated for their color development. Phenolic antioxidants together in combination with thiodipropionate compounds as synergists have been used for this purpose, e.g., n-octadecyl-3-(4'-hydroxy-3',5'-di-ferf-butylphenyl)propionate and dilauryl thiodipropionate (14). These systems have a tendency to develop colored impurities as a byproduct of their antioxidant function. The production of colored impurities becomes particularly evident in spray drying processes that utilize partially inert atmospheres (12). An improved antioxidant composition contains l,l,3-tris(2-methyl-4-hydroxy-5-tert-butyl phenyl)butane, (Topanol® CA). Here also in addition dilauryl thiodipropionate is used as a co-stabilizer (12).

11.5

Applications

11.5.1 Medical

Applications

There are impact modified acrylic-based polymer compositions intended for molding and extrusion of medical applications sold under the tradename Cyrolite® (15). These compositions have exceptional chemical resistance to fats and oils, good bonding and welding capabilities, including bonding to PVC tubing. Further, the compositions are characterized by good mechanical properties, a good transmission of visible light, and good resistance in sterilization methods. 11.5.2 Impact Modifiers MMBS is used typically as an impact modifier for a wide variety of resin compositions. Typical base materials are summarized in Table 11.3.

Methyl methacrylate/Butadiene/Styrene

Polymers

321

Table 11.3: Resins for Use of MMBS as Impact Modifier Matrix

Reference

PC+ styrene/maleic anhydride (MA) PC PC/siloxane copolymers PC + Polyethylene terephthalate)

(4) (16) (17) (18)

It has been found that the incorporation of a MMBS polymer into a composition containing a PC resin and a copolymer of MA and styrène facilitates the production of molded articles over a wide range of molding conditions without deleteriously affecting the strength or the thermal properties of the molded articles (4). Besides MMBS, also related copolymers, such as methyl methacrylate/acrylonitrile/butadiene/styrene and acrylonitrile/ethylene/ propylene/diene/styrene are impact modifiers for PC compositions (16). 11.5.3

Thermoforming

Applications

Blends of PC, ABS, and MMBS are useful to form articles with good impact and low gloss. The articles produced are useful as automotive components, bottles, and tool housings. A mixture of randomly branched carbonate polymers and linear carbonate polymers has been suggested (19). MMBS acts also as a melt strength enhancing agent. Chlorinated vinyl chloride-based compositions composed from chlorinated poly(ethylene) and MMBS are suitable for injection molding products with good heat resistance, impact strength, moldability, and surface properties (20). The addition of small amounts of methyl or phenyl poly(siloxane)s to blends of styrene/MA copolymers and MMBS copolymers enhances greatly the impact strength without having adverse influence on the heat resistance and surface luster (21). 11.5.4 Aqueous Additive

Systems

Aqueous additive systems provide a great degree of flexibility in the preparation of matrix resin blends and formulations (13).

322

Engineering Thermoplastics: Polyolefins and Styrenics

Further, the use of aqueous additive systems eliminates dust and compaction problems associated with the handling of powder form additives. Finally, the use of aqueous additive systems provides flexibility for mixing the additive with the resin. The additive can be mixed and dried with the resin still in moist, wet-cake form. It can be blended with other formulation ingredients, or pumped into an extruder or kneader during the compounding step. This flexibility can, in turn, provide still lower-cost processes and improved uniformity of mixing. An aqueous formulation can be prepared in general by contacting a matrix resin with the aqueous dispersion of the additive. The additive in aqueous dispersion is slowly absorbed by the resin particles. Eventually, the resin granules are separated from the aqueous phase by filtration, and dried by conventional methods (22). On the other hand, in situ polymerization of the matrix resin monomer in presence of a modifier latex is possible (23). Since MMBS additives are typically used in resin matrix formulations in small amounts of 0.1-15% and these additives are manufactured as aqueous emulsions containing roughly the same amount of water. The frictional heating of mixers, kneaders, and extruders can be used to remove efficiently this small amount of water. Therefore, elaborate and expensive isolation procedures are not needed, because mixing and drying can be combined into one step (13). 11.5.5

Prepregs

Fiber reinforced prepregs containing a MMBS modified thermoset resin are particularly useful in the fabrication of electrical and office equipment enclosures (24). Electrical and office equipment enclosures, such as computer cases, copier cases and telecommunications equipment, are conventionally prepared from thermoplastic resins such as PC, ABS, and poly(propylene). These materials have the advantageous properties of toughness, flexibility and the ability to meet the UL specifications by including fire retardant additives. However, the thermoplastics have the disadvantages of not being stiff due to their low modulus and a lack to flow into detailed molds due to their inherently high melt viscosity. Because of the relatively

Methyl methacrylate/Butadiene/Styrene

Polymers

323

high melt viscosities and the lower modulus, thicker wall sections and, in some cases, ribs must be designed into molded parts to provide adequate rigidity. These disadvantages can be overcome by using thermoset resins instead of thermoplastics. However, conventional thermoset resins, e.g., epoxies and phenolics, are not tough enough for these applications resulting in cracking due to their relatively low impact strength. Instead, a prepreg that is particularly suitable for the fabrication of electrical and office equipment has been developed. This prepreg consists of a thermoset, preferably a phenol formaldehyde resin, that is formulated with a MMBS resin. The MMBS resin is added to the phenolic novolak preferably at the stage of the condensation reaction of the phenolic resin. A composition is prepared by dissolving the MMBS modified thermoset resin in acetone. To the resulting solution, additives may be added, for example, pigments, flame retardants, lubricants or cure accelerators, e.g., hexamethylenetetramine. Suitable fire retardant materials include halogen compounds in combination with antimony compounds, including, tetrabromobisphenol A and antimony trioxide. Examples for halogen free flame retardants are phosphate esters, such as Hoechst Celanese® AP422 or Hoechst Celanese® IFR 23. The reinforcing filler for the prepreg may be fabricated of any discontinuous fiber, including carbon, glass, or Kevlar®. However, particularly good results are achieved with a thick carbon paper substrate. This material permits the prepreg manufacturer to achieve a higher throughput, and customers have fewer sheets to cut for a given charge weight. The preferred carbon paper is prepared from poly(acrylonitrile) fibers. The prepreg is prepared as the carbon paper from a roll is run at approximately 3 m min - 1 through a bath containing the resin solution. Then the impregnated paper is run through a pair of driven stainless steel nip rolls set at a gap of from 0.5 mm to remove excess resin solution and achieve the desired pick-up of 78-80% by weight of the resin solution. The acetone solvent is removed by running the paper through convection heat in a forced air oven at 110-120°C. The retention

324

Engineering Thermoplastics: Polyolefins and Styrenics Table 11.4: Physical Properties of a Prepreg (24) Property

Unit

Not modified

Flexural Strength Flexural Modulus Impact Energy Failure Tensile Strength Tensile Modulus Tensile Strain

MPa MPa

223 15.8 107 186 17.9 1.053

J/m

MPa GPa %

MMBS Modified 252 18.2 187 205 17.2 1.15

time in the convection heat zone is 8-12 min. A dry, tackless prepreg comprising about 80% solids by weight resin is eventually obtained. Molded articles may be prepared from the prepregs by compression and transfer molding. In general, several sheets of the prepreg are cut and stacked in a mold. For example, a prepreg was cured by heating for 80 s at 150-180°C at 100-200 bar. The cured sample had the physical properties shown in Table 11.4. 11.5.6 Powder Coatings Powder compositions for making powder coatings are made from a curable resin, such as an epoxy resin, and an agglomerate of a core-shell polymer, such as MMBS (25). The agglomerate is ground at liquid nitrogen temperature to form a reduced agglomerate, followed by extruding of the agglomerate together with the curable polymer. Then the extrudate is cooled and again ground. The powder compositions yield smooth, flexible 0.5-8 mil powder coatings with excellent appearance properties.

11.6 Suppliers and Commercial Grades Suppliers as well as commercial grades are shown in Table 11.5. Tradenames appearing in the references are shown in Table 11.6.

Methyl methacrylate/Butadiene/Styrene

Polymers

325

Table 11.5: Examples for Commercially Available MMBS Polymers (11) Tradename

Producer

Claradex 830 Cyrolite® G 20 HIFLO Denka Transparent Polymer TH-11 Paraloid® BTA-730 Metablen® MBS Kane Ace M-600 Clearstrength® MBS Nanostrength® MBS Spheroid®-P

Shin-A Corporation Evonik Röhm GmbH Denka Evonik Röhm GmbH Elf Atochem Kaneka Arkema Arkema LG Chem, Ltd.

Reference

(26) (27) (28)

326

Engineering Thermoplastics:

Tradename Description

Polyolefins

and

Styrenics

Table 11.6: Tradenames in References Supplier

Acrylite® MD Evonik Röhm Acrylic-based multipolymer (15) Acryloid® KM 581 Rohm & Haas MBS (4) Ancamine® (Series) Air Products & Chemicals Epoxy adduct of aromatic amine (25) Araldite® (Series) Epoxy resins Ciba (25) Calibre™ Dow PC (19) Cyasorb® 1164 Cytec Corp. 4,6-Bis-(2,4-dimethylphenyl)-2-(2,4-dihydroxyphenyl)-s-triazine (16,17) Cyasorb® 531 Cytec Corp. 2-Hydroxy-4-n-octyloxybenzophenone (16,17) Cyasorb® 5411 Cytec Corp. 2-(2H-Benzotriazol-2-yl)-4-(l,l,3,3-tetramethylbutyl)-phenol (16,17) Cyrolite® Evonik Röhm MBS (15) Doverlube® Dover Chemical Corp. Stereate based processing aids (16) Dowfax™ 2A1 Dow Alkyldiphenyloxide disulfonate (Surfactant) (13) Durastrength® 200 I Arkema Acrylic impact modifier (4) Dylark® Nova Chemicals S.A. (Arco Chemical Co.) Copolymers of styrene with maleic anhydride (4) Epon® (Series) Resolution Performance Products LLC. Corp. (Shell) Diglycidyl ethers of bisphenol A (25) Irgacure® 184 Ciba 1-Hydroxycyclohexylphenylketone (photo initiator) (25) Irgacure® 2959 Ciba l-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-lpropane-1-one, Photoinitiator (25) Irgacure® 819 Ciba 2,2-Dimethoxy-2-phenyl acetophenone (25)

Methyl methacrylate/Butadiene/Styrene

Polymers

Table 11.6 (cont): Tradenames in References Tradename Description

Supplier

Irgastat™ P18 Ciba Poly(ether-b-amide (antistatic agent) (16) Kane® Ace Kaneka MBS (4) Lexan® General Electric Poly(carbonate) (16) Makrolon® Bayer AG Poly(carbonate) (18) Merlon® Mobay Poly(carbonate) (4) Metablen® C Mitsubishi Rayon Co., Ltd. Butadiene based rubber (impact modifier) (4) Mylar® (Series) DuPont Poly(ethylene terephtalate) (12) Panipol® EB Panipol Oy Poly(aniline) (16,17) Paraloid® Rohm & Haas Acrylate rubber, impact modifier (19) Pebax® Arkema Poly(amide imide) (antistatic agent) (17) Pelestat® (Series) Sanyo Chemical Industries Poly(ether amide) (antistatic agent) (16,17) Plas-Chek™ 775 Ferro Epoxidized soybean oil (19) Polyoxyter® Polychem Alloy Inc. Processing aid (16) Resiflow® P-67 Estron Chemical, Inc. Poly(acrylic ester) based flow modifier (25) Stereon® Firestone SB copolymer (4) Uracros® ZW 3307 DSM Divinyl ether resin (25) Uvinul® 3030 BASF AG l,3-Bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3diphenyl-acryloyl)oxy]methyl]propane (UV absorber) (16,17) Viaktin® 3890 Solutia (Vianova) Acrylourethane resin (25)

327

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Engineering Thermoplastics:

Polyolefins

and

Styrenics

References 1. J.A. Brydson, "Plastics based on styrene," in Plastics Materials, chapter 16, pp. 425^65. Buttworth-Heinemann, Woburn, MA, 7th edition, 1999. 2. Impact modifiers: How to make your compound tougher, Plastics, Additives and Compounding, 6(3):46-49, June 2004. 3. L.A. Utracky, "Introduction to polymer blends," in L.A. Utracky, ed., Polymer Blends Handbook, Vol. 1, chapter 1, pp. 1-122. Kluwer Academic Publishers, Dordrecht, 2002. 4. L.G. Bourland, Polymeric molding composition containing styrenic copolymer, polycarbonate and MBS polymer, US Patent 4 696 972, assigned to Atlantic Richfield Company (Los Angeles, CA), September 29,1987. 5. S. Himei, M. Takine, and K. Akita, Blend of vinyl chloride resin and graft copolymer prepared by consecutive polymerization of monomers onto butadiene polymer, US Patent 3 288 886, assigned to Kanegafuchi Chemical Ind., November 29,1966. 6. D.H. Jones and W.J. Ferry, Methacrylate-butadiene-styrene graft polymers and process for their production, US Patent 3 985 704, assigned to Rohm & Haas Haas Company (Philadelphia, PA), October 12,1976. 7. K. Matschke, K.J. Rauterkus, D. Seip, and W. Zimmermann, Process for the preparation of a dispersible vinyl acetate/ethylene polymer powder, US Patent 3 883 489, assigned to Hoechst Aktiengesellschaft (Frankfurt am Main, DT), May 13,1975. 8. T.D. Goldman, Isolation and improvement of impact modifier polymer powders, US Patent 4 278 576, assigned to Rohm and Haas Company (Philadelphia, PA), July 14,1981. 9. E.J. Troy and A. Rosado, Preparation of butadiene-based impact modifiers, US Patent 5534594, assigned to Rohm and Haas Company (Philadelphia, PA), July 9,1996. 10. L.K. Molnar, MBS impact modifiers, US Patent 6331580, assigned to Rohm and Haas Company (Philadelphia, PA), December 18,2001. 11. IDES Integrated Design Engineering Systems, The Plastics Web®, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/prospector/, 2006. 12. R.R. Clikeman, D.H. Jones, T.J. Shortridge, and E.J. Troy, Methyl methacrylate-butadiene-styrene impact modifier polymers, polyvinyl chloride, compositions and methods, US Patent 4 379 876, assigned to Rohm and Haas Company (Philadelphia, PA), April 12,1983. 13. R.H. Weese, C.-S. Chou, E.P Dougherty, J.M. Brady, and D.J. McDonald, Aqueous additive systems for polymeric matrices, US Patent

Methyl

14. 15.

16.

17.

18.

19. 20. 21. 22. 23. 24. 25. 26.

methacrylate/Butaáiene/Styrene

Polymers

329

7309 729, assigned to Rohm and Haas Company (Philadelphia, PA), December 18,2007. N.N., Vinyl chloride resin composition, GB Patent 1 536399, assigned to Kureha Chemical Ind. Co. Ltd., December 20,1978. Evonik Cyro LLC, CYROLITE®, ACRYLITE® and XT® Polymers. The world's most advanced medical acrylics, Technical Information 3578-0209-1BR, Evonik Cyro LLC, Parsippany, NJ, 2009. [electronic:] http://www.plexiglas.de/NR/rdonlyres/ 05BBC966-9BED-4B67-A72A-86B33437718F/0/ 3578MedicalPolymersbrochure.pdf. J. Chen, T.L. Hoeks, K. Inoue, and D. Shen, Polycarbonate compositions and articles formed therefrom, with matte surfaces and high light transmissions, US Patent 7 514 523, assigned to SABIC Innovative Plastics IP B.V. (Bergen op Zoom, NL), April 7, 2009. J.F. Hoover, J.-P. Lens, and B. Mullen, Polycarbonate-polysiloxane copolymers, method of making, and articles formed therefrom, US Patent 7524 919, assigned to SABIC Innovative Plastics IP B.V. (Bergen op Zoom, NL), April 28, 2009. X. Li, PR. Moulinie, and J.P. Mason, Thermoplastic molding composition having improved toughness at low temperatures and surface appearance, US Patent 7524898, assigned to Bayer Material Science LLC (Pittsburgh, PA), April 28,2009. M.K. Laughner, Molding compositions with methyl (meth)acrylatebutadiene-styrene graft copolymers, US Patent 5 087 663, assigned to The Dow Chemical Company (Midland, MI), February 11,1992. T. Suzuki, Chlorinated vinyl chloride resin composition, US Patent 7332544, assigned to Kaneka Corporation (Osaka, JP), February 19, 2008. R. Okumura, E. Terada, and S. Kawazoe, Thermoplastic resin composition, US Patent 4957964, assigned to Idemitsu Petrochemical Co., Ltd. (Tokyo, JP), September 18,1990. T. Neubert, Preparation of resin encapsulated crumb rubber, US Patent 3813259, assigned to Goodyear Tire & and Rubber, May 28,1974. H. Kitamura, K. Kurimoto, and K. Azuma, Process for the preparation of vinyl chloride-based resins, US Patent 4272424, assigned to Shin-Etsu Chemical Co., Ltd. (Tokyo, JP), June 9,1981. M.T. Choate, Composite material, US Patent 5607769, assigned to Fiberite, Inc. (Tempe, AZ), March 4,1997. C.S. Ilenda, M.L. Spera, G. Tullos, and A.T. Daly, Smooth, flexible powder coatings, US Patent 6861475, assigned to Rohm and Haas Company (Philadelphia, PA), March 1, 2005. Elf atochem starts additives plant, Plastics, Additives and Compounding, 2(l):4-4, January 2000.

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Engineering Thermoplastics: Polyolefins and Styrenics

27. Additives to the fore at k 2004, Plastics, Additives and Compounding, 6 (6):32-41, 2004. 28. New impact modifier offers cost and performance efficiencies, Plastics, Additives and Compounding, 11(2):6, March-April 2009.

12 Acrylonitrile/Styrene/ Acrylate Polymers The earliest preparation on an acrylonitrile-styrene-acrylate (ASA) polymer is believed to have taken place in 1964 (1,2). ASA was first introduced to the market by BASF in around 1970 as Luran® S, based on patents from the 1960s (3-6). The reason for the development was to create a material similar to acrylonitrile-butadiene-styrene (ABS) however, the weather resistance should be superior. ASA polymers are produced by introducing a grafted acrylic ester elastomer during the copolymerization reaction between styrene and acrylonitrile.

12.1

Monomers

Monomers for ASA polymers are shown in Table 12.1 and in Figure 12.1. Table 12.1: Monomers for Acrylonitrile/Styrene/Acrylate Polymers Monomer

Remarks

Styrene Acrylonitrile n-Butyl acrylate Methyl methacrylate Dihydrodicyclopentadienyl acrylate Allyl methacrylate

Basic monomer Basic monomer Improves weatherability (7,8) Common (8) Crosslinker (9) Crosslinker

331

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Engineering Thermoplastics: Polyolefins and Styrenics

-C-N Acrylonitrile

Styrène

Methylmetacrylate

Allyl metacrylate

h n-Butyl acrylate

Dihydrodicyclopentadienyl acrylate

Figure 12.1: Monomers used for Acrylate/Styrene/Acrylonitrile Polymers M-Butyl acrylate is produced by reacting acrylic acid with n-butanol in liquid phase in contact with an acid cation exchanger as a catalyst (10,11). Allyl acrylate is produced from acrolein (12). This type of reaction is actually a Claisen-TiScenko reaction. In contrast, allyl methacrylate is produced by the esterification of methacrylic acid and allyl alcohol (13), or by the transesterification of allyl alcohol with an ester of methacrylic acid, preferably with methyl methacrylate. The latter reaction is catalyzed with zirconium acetylacetonate (14). The esterification reactions are shown in Figure 12.2.

12.2 Polymerization and Fabrication Most commonly, in the ASA manufacturing process, three distinct polymerization reactions or stages are involved (15). The third stage can be combined with the second so that at sketchily the polymerization procedure appears as a two stage process. In the first stage, the elastomeric component, typically a poly(alkyl acrylate) rubber, is produced. This reaction can be carried out either in a water-based emulsion or in a solution polymerization process. In the second stage, the styrene and acrylonitrile monomers are

Acrylonitrile/Styrene/Acrylate

^γ°

Η+0

Polymers

333

.0

γ^

^

\

Figure 12.2: Synthesis of Allyl acrylate and Allyl methacrylate copolymerized and grafted onto the elastomeric phase to achieve the desired compatibility. This stage can be performed either in emulsion, bulk, suspension, or as a mixed process. In the third stage, styrene and acrylonitrile - and, optionally, other monomers - are copolymerized, either simultaneously with the second, i.e., grafting, or separately in an independent operation, to form the rigid matrix. Again, this polymerization may be carried out in emulsion, bulk, or suspension (15). The specific properties of the resulting polymers can be tailored by adding, special acrylate, monovinylidene aromatic, and ethylenically unsaturated nitrile monomers. 12.2.1

Two Stage Preparation for Structured Latexes

ASA structural latexes have been synthesized in a two stage seeded emulsion polymerization. In the first stage, partially crosslinked poly(w-butyl acrylate) and poly(«-butyl acrylate-sfaf-2-ethylhexyl acrylate) rubber cores are synthesized. In the second stage, a hard styrene acrylonitrile copolymer (SAN) shell is grafted onto the rubber seeds (16). Characterization of the polymer indicates that an application of sodium dodecyl sulfonate as anionic surfactant and sodium persulfate as initiator for both stages leads to a hemisphere particle

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morphology. The same is true, when ferf-butyl hydroperoxide is used for the first stage and sodium persulfate is used for the second stage. In contrast, raspberry and core shell structures are formed when in both stages a non ionic surfactant, i.e., nonylphenol ethoxylated poly(ethylene glycol) and sodium persulfate are used. 12.2.2

Three Stage Preparation

High impact strength thermoplastic resins can be prepared by mixing a styrene/acrylonitrile copolymer with rubber particles. In general, the styrene/acrylonitrile copolymer is prepared by the graft copolymerization of styrene and acrylonitrile in the presence of rubber itself (17). The high impact strength thermoplastic resin exhibits different characteristics. According to the rubber used in the composition, the properties of the final product can be tailored to some extent. Frequently, a butadiene polymer is added as rubber component, resulting in a ABS type polymer. The ABS polymer thus obtained has an excellent impact strength even at a very low temperature. However, it exhibits a poor weather resistance and aging resistance. In order to produce a resin with excellent impact strength and at the same time excellent weather resistance and aging resistance, it is essential to eliminate the unsaturated ethylene polymer from the graft copolymer. Therefore, ASA polymers that are crosslinked with the alkyl acrylate rubber polymer are preferred (17). The acrylate/styrene/acrylonitrile graft copolymer can be prepared by the conventional emulsion polymerization. After the polymerization process the graft copolymer can be recovered in powder form after coagulating and spray drying. A coagulant is added to the emulsion. This is followed by washing, dehydrating and drying to give the graft copolymer in dried powder form. In this way, a latex seed is obtained. An exemplary feed for emulsion polymerization is shown in Table 12.2. The reaction temperature is raised without the potassium persulfate to 70°C and only then the potassium persulfate is added to start the reaction. The reaction is completed after one hour to yield a seed with a mean diameter of 200 nm. In the second step, an alkyl

Acrylonitrile/Styrene/Acrylate

Polymers

335

Table 12.2: Preparation of a ASA Rubber via a Latex Seed (17) Component

Amount Parts by weight Stepl

«-Butyl acrylate Sodium dodecyl sulfate Ethylene glycol dimethacrylate Allyl methacrylate Sodium hydrogen carbonate Distilled water Potassium persulfate

10 0.03 0.05 0.02 0.1 60 0.05

Step 2 Seed latex from Step 1 n-Butyl acrylate Sodium dodecyl sulfate Ethylene glycol dimethacrylate Allyl methacrylate Distilled water Potassium persulfate

40 0.5 0.1 0.05 50 0.05

acrylate rubber polymer is prepared from the seed. The mean diameter of the alkyl acrylate rubber polymer obtained from the second reaction is 450 nm (17). Finally, the ASA graft copolymer is prepared. To the alkyl acrylate rubber polymer obtained as described just above, styrene and acrylonitrile are added in the desired quantities. Dodecylmercaptan and potassium persulfate are added as chain transfer agent and radical initiator, respectively. An ASA copolymer with a mean diameter of 550 nm is obtained. 22.2.3

Blends

The most widely utilized method to improve the appearance properties of an ASA resin, is to blend the ASA resin with a second resin, which can supplement the weak properties of former resin. For example, blending with poly(methyl methacrylate) (PMMA) has been suggested. PMMA exhibits excellent weatherability, mechanical properties and surface scratch resistance and thus, is widely

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Engineering Thermoplastics: Polyolefins and Styrenics

used in outdoor products. The compatibility of ASA with PMMA has been reported (18,19). Further, methods for producing a thermoplastic resin with good physical properties and appearance properties and weatherability as well, use a three component blend of ASA, PMMA, and polycarbonate) (20). Products with improved properties use instead pure PMMA a terpolymer from 1,3-butadiene, styrene, and methyl methacrylate (8). Actually, the proposed blend consists of up to 6 components of copolymers of different composition and particle diameters. Such thermoplastic resin compositions have excellent basic physical properties, weatherability and good appearance properties, such as scratch resistance, color stability and gloss. Compositions made from pellets of ASA, vinyl chloride containing polymers, and wood can be extruded to form weatherable products or materials (21). Weatherable styrenic blends with improved translucency have been reported to be made from several components (15). It has been found that there is a synergistic effect in reducing opacity of the blend, when a mixture of PMMA and methyl methacrylate-styreneacrylonitrile terpolymer (MMASAN) is used as compared to using PMMA or MMASAN alone. Weatherable ASA blends with bright intense colors, reduced usage of color pigments, and achievement of better depth of the color are possible, by utilizing existing inorganic pigments, organic pigments and dyes. In addition to improved translucency with better colorability, an improved weathering performance can also be expected for the mixture compared to MMASAN alone and improved physical properties can be expected for the mixture compared to PMMA alone. Example formulations are shown in Table 12.3 The use of poly(alkylene oxide)s in ASA molding compositions results in improved properties. They reduce the susceptibility to electrostatic charging, improve the flowability and reduce Shore hardness (9).

12.3

Properties

ASA has great toughness and rigidity, good chemical resistance and

Acrylonitrile/Styrene/Acrylate

Polymers

337

Table 12.3: Formulations with Improved Translucency (15) Formulation ASA/PMMA/MMASAN ASA/PMMA/MMASAN ASA/PMMA/MMASAN ASA/PMMA ASA/MMASAN

PMMA/SAN 75/25 50/50 25/75 100/0 0/100

Opacity 90.21 89.11 90.80 92.98 94.18

Table 12.4: Properties of a n ASA P o l y m e r 3 (22) Property

Value

Density

1.07

Tensile Creep Modulus (1000 h) Tensile Creep Modulus (1 h) Tensile Modulus Tensile Stress at yield (23°C) Flexural Strength (23°C) Dielectric Constant (100 Hz) a Luran™ S 757 G, BASF

1,650 2,200 2,400 51 75 3.4

Unit gem" 3

MPa MPa MPa MPa MPa

thermal stability, outstanding resistance to weather, aging and yellowing, and high gloss. The properties and the methods of characterization of the of the ASA family are standardized (23). Some selected properties of an ASA polymer are shown in Table 12.4.

12.3.1 Mechanical

Properties

The structure and mechanical properties of ASA and blends of ASA and poly(butylene terephthalate) (PBT) have been studied. 40/60 and 60/40 blends of ASA/PBT are composed of two phases, thus are dispersed, while a 50/50 blend shows a cocontinuous structure. With increasing processing temperature, the mechanical properties decrease, probably due to the degradation of PBT in the course of processing. The mechanical properties do not as much decrease for blends with a continuous structure (24).

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Engineering Thermoplastics: Polyolefins and Styrenics

Table 12.5: Gas Permeation Coefficients of Luran® S 776 (25) Permeability coefficient [cm3mmm"2d"l atm"1 ] N2

32.3.2

02

H20

C0 2

H2

CH4

10.1 55.7 3.5 223 23°C, DIN 53380 (26)

507

10.1

Optical Properties

Luran® S and Geloy® exhibit a high resistance to weathering. The the effects of UV light and weather on ASA type polymers have been reviewed (27). The rates of gloss loss and color shift for a series of aromatic engineering thermoplastics, among others, also five ASA samples have been compared at different global sites. Temperature, humidity, rainfall, and acid rain seemed to play minor roles for most polymers (28). 12.3.3

Chemical Properties

Objects molded from classic ABS or ASA copolymers are generally severely attacked by numerous chemical products, such as acids like acetic acid, butyric acid, and nitric acid, phthalates like dioctyl phthalate, gasoline, greases, inks, iodine, alcohols like methanol, motor oils, phenols, glycols, tetrachloroethylene, and acetates like ethyl acetate, amyl acetate, and others (29). Compositions based on ASA, ABS and SAN have been described and tested with respect to their chemical resistance. ASA types are comparatively impermeable to gases. The gas permeation coefficients of a selected ASA type is shown in Table 12.5.

12.4 Special Additives In general, all common additives for polymers can b e used for ASA formulations, such as processing additives, UV stabilizers, flame

Acrylonitrile/Styrene/Acrylate

Polymers

339

Table 12.6: ASA with Improved Weatherability (30) Additives

/o

Conventional Composition Titanium dioxide Poly(ethylene terephthalate) or PBT UV stabilizer ASA

3.0 4.5-6.0 0.9-1.0 rest

Improved Composition Titanium dioxide Nylon 6,6 UV stabilizer ASA

3.0 6.0 0.9-1.0 rest

retardants and others. Some additives deserve a special discussion that follows subsequently. 22.4.3

Weatherability

Improvers

Because of the intended outdoor applications of ASA materials, improved weatherability and color retention performance are of importance. These properties can be enhanced by additives. An attempt to improve the weatherability performance has been to increase pigmentation, particularly T1O2. However, this additive contributes to the overall opacity, and therefore reflectivity and weatherability, of the resultant exterior siding. This method was disadvantageous because the light resistance of T1O2 pigmentation over exposure to weathering seemed to be inadequate. Traditional ASA compositions and such with improved weatherability are shown in Table 12.6. The nylon 6,6 compounds are added as the color retention agent in place of the poly(ester)s of the conventional composition (30). 12.4.2 Gloss Reducers Products prepared of thermoplastic molding compositions are often times glossy, yet for some applications this is not a desirable

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Engineering Thermoplastics: Polyolefins and Styrenics

property. Therefore there is a considerable need for low gloss compositions, especially in applications, such as computer housings, keyboards, appliances and automotive parts (31,32). Gloss reducers are sometimes addressed as dulling agents (33). Elimination of gloss by surface embossing has been practiced but requires a separate step and adds cost. Moreover, subsequent abrasion may remove the embossed surface and cause the gloss to reappear (31). Addition of a finely divided filler, such as silica, silicate or alumínate has been demonstrated to reduce the gloss of thermoplastic molding compositions yet this is often accompanied by an undesirable reduction in the level of at least some physical and/or mechanical properties of the molded article. Another straightforward method to reduce the gloss consists in admixing a dull graft copolymer as dulling agent (33). Such copolymers may be prepared from n-butyl acrylate, allyl methacrylate, and hydroxypropyl methacrylate. Likewise, hydroxypropyl methacrylate may be substituted by maleic anhydride. The polymerization is started by 2,2'-azobisisobutyronitrile and peroxides. Special additives that are reducing the gloss are copolymers of ethylene/glycidyl methacrylate (GMA) or ethylene/methyl acrylate/ GMA together with a primary poly(propylene oxide)triamine or a primary poly(propylene oxide)diamine. The glycidyl containing copolymers have molecular weights around 20 kDalton, whereas the poly(amine)s have molecular weights around 2 kDalton. In the final ASA composition the epoxy and the amine functionalities are lined together. The coupling reaction may occur prior thermal processing or during the thermal processing, e.g. extrusion (31).

22.4.3 Heat Distortion Improving

Agents

The modification of a poly(ester)/ASA resin with a heat distortion improving agent results in glass filled blends that have improved heat distortion properties in comparison to a poly(ester) resin without this additive. Further, the blends have high impact strength, good stiffness and mechanical properties along with good appearance and processability.

Acrylonitrile/Styrene/Acrylate

Polymers

341

Table 12.7: Heat Distortion Improving Agents (34) Compound Talc Salt of carboxcylic acid Poly(esteramide) Phthalocyanines N,N'-Bis(methoxycarbonylbenzoyl)-l,4-butanediamine Alkali metal carbonates Alkaline earth metal carbonates Poly(tetrafluoroethylene) Typical examples of heat distortion improving agents are shown in Table 12.7. The agent is incorporated in amounts of 0.01-3%. In addition, ASA may be blended with other polymers that themselves exhibit high heat distortion temperatures. For example, blends of poly(ether imide) and ASA exhibit an improved heat distortion temperature, improved flexural properties and tensile properties in comparison to the ASA component alone and have lower impact strengths as well (35). The statement above has been exemplified using Ultem® 1000 as a poly(ether imide) resin and Geloy® 1020 as ASA component. Conversely, ASA itself may serve as a heat distortion improver additive for poly(vinyl chloride) (PVC) (36). The increase of the heat distortion temperature is linearly dependent on the amount of ASA added. Therefore, it is easy to add just the amount needed without doing a lot of preliminary testing with various formulations. ASA can be used in a blend with PVC. Another approach is the coextrusion of the ASA with PVC in such a way that only ASA is exposed to high temperatures.

12.5

Applications

Because of the enhanced weather resistance, ASA is used extensively in the automotive industries, and further in general for outdoor applications. In particular, ASA polymers have been widely applied to glossy colored outdoor products including (17): • Automotive outside parts, • Boats,

342

Engineering Thermoplastics: Polyolefins and Styrenics • • • •

Garden furniture, Household electrical products, Satellite antennas, or Street lamps,

12.5.3 Multilayer

Laminates

Thermoformable multilayer laminates are known in the vehicular arts as providing acceptable surface preparation when applied to various automobile components without distorting the quality of the underlying surface or substrate. Multilayer laminates have traditionally been formed in a variety of methods, including (37): • • • • •

Co-injecting molding, Overmolding, Multi-shot injection molding, Sheet molding, or Co-extrusion, placement of a film of coating layer material on the surface of a substrate layer.

Co-extrusion methods are especially desirable. Multilayer laminates formed by co-extrusion are advantageous economically and generally exhibit improvements in cohesion and adhesion relative to the various layers making up the multilayer laminate. Thermoplastic multilayer laminate composed from an outer layer of resorcinol arylate poly(ester)s, a middle layer comprising a polycarbonate), e.g., LEXAN® 131, and an inner-tie layer made from ASA or ABS have been described (37). Resorcinol arylate poly(ester)s may be understood as an isophthalic terephthalic resorcinol bisphenol A copolymer. 12.5.2

Roofing Material

A composition of materials has been described that can be extruded into sheets to form panels to create a roofing system (38). The panels are capable to interlock mutually in order to provide a substantially weatherproof alignment The sheet member has a top layer made of ASA and a bottom layer made of formulated PVC. The two layers are extruded and bonded by pressure or lamination or

Acrylonitrile/Styrene/Acrylate

Polymers

343

co-extruded. Eventually, the bonded materials are thermoformed to resemble more popular types of roof coverings such as shakes, shingles or tiles. The ASA used exhibits special characteristics with respect to mechanical properties. Naturally, a high resistance to weathering is required. An example for an impact modified weatherable, copolymer with resistance to weathering, aging, and yellowing, is Luran® S 776. PVC is formulated by several additives including impact modifiers, lubricants, heat stabilizers, pigments, flame retardant, plasticizers, and processing aids. Epoxidized soybean oil, plasticizers and heat stabilizers are used to prevent degradation caused by the heat of processing. Pigments are added to achieve coloring. A flame retardant is added to provide a substantially flame retardant product. The additives used are given in more detail elsewhere (38). 12.5.3 Antimicrobial

ASA

In 2008, an antimicrobial ASA plastic type was introduced (39). This was the first ASA type with antimicrobial properties. The antimicrobial material contains silver compounds that are incorporated into the plastic in order to impart its surface with a germicidal effect. Interesting areas of application are not only hand dryers, soap dispensers or entire sanitary units in public washroom facilities, but in general articles that come into contact with bacteria and other microorganisms and that need to be sterile. These include hospital beds, medical treatment chairs or computer keyboards in public offices.

12.6 Suppliers and Commercial Grades Suppliers as well as commercial grades are shown in Table 12.8. Tradenames appearing in the references are shown in Table 12.9.

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Engineering Thermoplastics: Polyolefins and Styrenics

Table 12.8: Examples for Commercially Available ASA Polymers (40) Tradename

Producer

ABEL ASA 911001 Alcomb ASA Blendex® Geloy® Luran® S

Shanghai Hongjinyin Industry Co., Ltd. Albis Plastic GmbH Chemtura SABIC Innovative Plastics BASF

Shinko® Lac Starex® Ultradur® S Luran® S BX 13042

Mitsubishi Rayon America Inc. Cheil Industries, Inc. BASF BASF

Tradename Description

Remarks

PC blended High impact Outdoor Luran® without S is SAN PBT+ASA Antimicrobial (39)

Table 12.9: Tradenames in References Supplier

Aerosol® OT Cytec Industries, Inc. Sodium sulfosuccinic acid dioctyl ester (9) Geloy® resin General Electric ASA copolymer (35,37) Lexan® General Electric Poly(carbonate) (37) Lupolen® (Series) BASF AG Poly(ethylene) (9) Lustran® Bayer AG ABS copolymer (21) Tyril® Dow ABS copolymer (21)

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Polymers

345

References 1. J.A. Herbig and I.O. Salyer, Binary blends of styrene/acrylonitrile copolymer and butyl acrylate/acry-lonitrile copolymer and methods for preparing the same, US Patent 3118 855, assigned to Monsanto Chemicals, January 21,1964. 2. J. Scheirs, "Historical overview of styrene polymers," in J. Scheirs and D. Priddy, eds., Modern styrenic polymers: Polystyrenes and styrenic copolymers, Wiley Series in Polymer Science, chapter 1, pp. 3-24. John Wiley, Chichester, 2003. 3. H.-W. Otto, Thermoplastische Formmassen auf der Basis von Styrol und Acrylnitril, DE Patent 1182811, assigned to BASF AG, December 03,1964. 4. H. Willersinn, H.-W. Otto, P. Raff, and L. Schuster, Schlagfeste Thermoplastische Formmassen, DE Patent 1260135, assigned to BASF AG, February 01,1968. 5. B. Vollmert, Impact-resistant plastic compositions comprising a styrene polymer and a cross-linked acrylic acid ester polymer, and process for preparing same, US Patent 3 055 859, assigned to BASF AG, September 25,1962. 6. H.P Siebel and H.-W. Otto, Styrene- acrylonitrile copolymers blended with graft copolymers of styrene onto butadiene-alkyl acrylate-vinyl alkyl ether terpolymers, US Patent 3280 219, assigned to BASF AG, October 18,1966. 7. M.C.O. Chang and R.M. Auclair, Weatherable ASA composition, US Patent 5 990 239, assigned to Bayer Corporation (Pittsburgh, PA), November 23,1999. 8. D.-S. Kim, C.-H. Lee, S.-L. Kim, and H.-J. You, Thermoplastic resin composition having improved external appearance and excellent weatherability, US Patent 7514502, assigned to LG Chem, Ltd. (KR), April 7, 2009. 9. N. Guntherberg, G. Lindenschmidt, and N. Niessner, Thermoplastic molding materials, US Patent 6649117, assigned to BASF Aktiengesellschaft (Ludwigshafen, DE), November 18,2003. 10. H. Erpenbach, K. Gehrmann, H. Joest, and P. Zerres, Continuous production of n-butylacrylate free from dibutylether, US Patent 4012 439, assigned to Hoechst Aktiengesellschaft (Frankfurt am Main, DT), March 15,1977. 11. A. Riondel and J. Bessalem, Process for preparing butyl acrylate by direct esterification, US Patent 6 846 948, assigned to Arkema (Puteaux, FR), January 25,2005. 12. E.A. Youngman and F.F. Rust, Production of allyl acrylate from acrolein, CA Patent 708634, assigned to Shell Oil Co., April 27,1965.

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13. K. Tamura and S. Suzuki, Method for producing (meth)allyl (meth)acrylate, JP Patent 2 005 314 248, assigned to Mitsubishi Rayon Co. and Osaka Organic Chem. Ind., November 10, 2005. 14. B. Schmitt, G. Protzmann, T. Schuetz, H. Trauthwein, R. Martin, J. Knebel, I. Sander, K. Gottmann, T. Kehr, D. Bathen, and C. Maul, Method for synthesizing allyl methacrylate, WO Patent 2 009 003 746, assigned to Evonik Roehm GmbH, Schmitt Bardo, Protzmann Guido, Schuetz Thorben, Trauthwein Harald, Martin Reinhold, Knebel Joachim, Sander Ingo, Gottmann Klaus, Kehr Thomas, Bathen Dieter, and Maul Christian, January 08, 2009. 15. S.K. Gaggar and K. Hongladarom, Weatherable styrenic blends with improved translucency, US Patent 6 720 386, assigned to General Electric Company (Pittsfield, MA), April 13,2004. 16. S. Tolue, M.R. Moghbeli, and S.M. Ghafelebashi, Preparation of ASA (acrylonitrile-styrene-acrylate) structural latexes via seeded emulsion polymerization, Eur. Polym. /., 45(3):714-720, March 2009. 17. T.-B. Ahn, H.-T. O, J.-T. Park, M.-J. Kim, and K.-H. Yoo, Thermoplastic resin composition, US Patent 7417088, assigned to LG Chem, Ltd. (KR), August 26,2008. 18. M. Fowler, J. Barlow, and D. Paul, Effect of copolymer composition on the miscibility of blends of styrene-acrylonitrile copolymers with poly (methyl methacrylate), Polymer, 28(7):1177-1184, June 1987. 19. R. Schäfer, J. Zimmermann, J. Kressler, and R. Mülhaupt, Morphology and phase behaviour of poly(methyl methacrylate)/poly(styrene-coacrylonitrile) blends monitored by fti.r. microscopy, Polymer, 38(15): 3745-3752, July 1997. 20. C.-J. Chen and M.J. Sierodzinski, Weatherable molding composition having improved surface appearance, US Patent 6 476126, assigned to Bayer Corporation (Pittsburgh, PA), November 5, 2002. 21. R.E. Hughes and T.B. Hughes, Extrudable compositions and processes for producing same, US Patent 7378462, assigned to Hughes Processing, Inc. (Costa Mesa, CA), May 27, 2008. 22. BASF, Product information, [electronic:] http://iwww.plasticsportal.com/products/datasheet. html?type=iso¶m=Luran+S+757+G, 2009. 23. Plastics - acrylonitrile-styrene-acrylate (ASA), acrylonitrile-(ethylene-propylene-diene)-styrene (AEPDS) and acrylonitrile-(chlorinated polyethylene)-styrene (ACS) moulding and extrusion materials - Part 1: Designation system and basis for specifications, ISO Standard 6402-1, International Organization for Standardization, Geneva, Switzerland, 2002. 24. C M . Benson and R.P. Burford, Morphology and properties of acrylate styrene acrylonitrile/polybutylene terephthalate blends, /. Mater. Sei.,

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Polymers

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30(3)573-582, January 1995. 25. L.K. Massey, "Polyisobutylene rubber," in Permeability Properties of Plastics and Elastomers: A Guide to Packaging and Barrier Materials, chapter 80, p. 469. William Andrew Publishing, Norwich, NY, 2nd edition, 2003. 26. Testing of plastics - determination of gas transmissions rate - Part 1: Volumetrical method for testing of plastic films, DIN Standard DIN 53380, Beuth Verlag, Berlin, 2000. 27. L.K. Massey, "Acrylonitrile-styrene-acrylate," in The Effects ofUV Light and Weather on Plastics and Elastomers, chapter 4, pp. 47-56. William Andrew Publishing, Norwich, NY, 2nd edition, 2006. 28. J. Pickett, M. Gardner, D. Gibson, and S. Rice, Global weathering of aromatic engineering thermoplastics, Polym. Degrad. Stab., 90(3):405417, December 2005. 29. J.-M.G.L. Dumont, Composition of ABS and/or ASA copolymers and SAN copolymers with high chemical resistance, US Patent 6 403 723, assigned to General Electric Company (Pittsfield, MA), June 11, 2002. 30. G.J. Kogowski, H. Goerrissen, and G.E. McKee, Method of improving the weatherbility and color retention performance of styrene copolymer compositions, US Patent 6 482 893, assigned to BASF Corporation (Mt. Olive, NJ), November 19, 2002. 31. M.-C.O. Chang and A.R. Padwa, Low gloss ASA resin, US Patent 6395828, assigned to Bayer Corporation (Pittsburgh, PA), May 28, 2002. 32. M.-C.O. Chang, A.R. Padwa, C.-J. Chen, and D. Dufour, Weatherable resin compositions having low gloss appearances, US Patent 6 982 299, assigned to Lanxess Corporation (Pittsburgh, PA) and Bayer Aktiengesellschaft (Leverkusen, DE), January 3,2006. 33. G.E. Mc Kee, B. Rosenau, and W. Heckmann, Casting compounds for the production of mouldings with reduced surface gloss, US Patent 6103829, assigned to BASF Aktiengesellschaft (Ludwigshafen, DE), August 15, 2000. 34. E. Cheret, R. De Vries, F. Mercx, and V. Kwiecinski, Polyester molding composition, US Patent 6242519, assigned to General Electric Company (Schenectady, NY), June 5, 2001. 35. H.F. Giles, Jr. and W.R. Schlich, Polyetherimide-ASA blends, US Patent 5070142, assigned to General Electric Company (Pittsfield, Mass.), December 3,1991. 36. C. DeArmitt, Raising the softening point of PVC, Plastics, Additives and Compounding, 6(4):32-34, July-August 2004. 37. M.S. Davis, M. Lindway, M.T. Roland, J.A. Suriano, H. Wang, V.H. Watkins, G.S. Zafiris, and H. Zhou, Formable thermoplastic multilayer laminate, a formed multi-layer laminate, an article, and a method

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and

Styrenics

of making an article, US Patent 7514147, assigned to Sabic Innovative Plastics IP B.V. (NL), April 7,2009. 38. F.L. Italiane and J. Sciarra, III, Composition of a weatherproof roofing material, US Patent 6 536177, March 25, 2003. 39. BASF launches antimicrobial ASA copolymer, Plastics, Additives and Compounding, 10(6):19, November-December 2008. 40. IDES Integrated Design Engineering Systems, The Plastics Web®, IDES Inc. 209 Grand Avenue Laramie, WY 82070 USA [electronic:] http://www.ides.com/prospector/, 2006.

Index Tradenames Aclon™ 1180 Poly(chlorotrifluoroethylene), 66 Acrylite® MD Acrylic-based multipolymer, 326 Acryloid® KM 581 MBS, 326 Aerosol® OT Sodium sulfosuccinic acid dioctyl ester, 344 Affinity® Metallocene catalyzed polymers (MCP), long chain LLDPE, 66 Ageless® Iron oxide, 101 AgeRite™ Resin D Antioxidant, 178 Airflex® (Series) Vinyl-ethylene emulsions, 205 Airvol® (Series) Poly(vinyl alcohol)s, 205 Alathon® Poly(ethylene), 133 Albrite® Phosphorus containing chemicals, 101 Alkamuls® EGDS Glycol distearate, 101 Alkamuls® EL-620 Sorbitan monooleate, 101 Alkamuls® GMS Glycerol monostearate, 101 Alkamuls® JK Guerbet ester, 101 Alkamuls® SML Sorbitan monoester, 101 349

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Polyolefins

and

Styrenics

Alkamuls® SMO Sorbitan monooleate, 101 Alkamuls® STO Sorbitan trioleate, 101 Amgard® TOF Phosphate ester (Flame Retardant), 101 Amilan® CM1017C Nylon 6, 147 Ancamine® (Series) Epoxy adduct of aromatic amine, 326 Antiblaze (Series) Flame retardant, 284 Araldite® (Series) Ciba, 326 ARCOprime® 400 Mineral oil, 101 Atmer® Antistatic agent, 147 Attane® Resins Ultra low density poly(ethylene), 66 Bayblend® FR2010 PC/ABS terpolymer, 246 Baydur® Poly(urethane), 147 Bayflex® (Series) Poly(urethane), 147 Blendex® 446 Batch of SAN and Teflon, 246 Blendex® ABS ABS copolymer, 246 Bruggolite® FF 6 Reducing agent, 205 Budene® 1207 Poly(butadiene), 98% cis-1,4, 178 Buna® (Series) EPDM, 284 Bynel® (Series) Anhydride modified ethylene vinyl acetate resin, adhesion promoter, 205 Calibre™ PC, 326 Carbowax® (Series) Poly(ethyleneoxide glycol) (PEG), 205

Index

351

Chimassorb® 81 2-Hydroxy-4-(octyloxy)benzophenone, 34 Chimassorb® 944 Hindered amine light stabilizer (CAS 71878-19-8), 284 Crillet® I poly(oxyethylene) sorbitan monolaureate, 147 Crossfire® Crosslinked Poly(ethylene), 101 Cyasorb® 1164 4,6-Bis-(2,4-dimethylphenyl)-2-(2,4-dihydroxyphenyl)-s-triazine, 284, 326 Cyasorb® 531 2-Hydroxy-4-n-octyloxybenzophenone, 311, 326 Cyasorb® 5411 2-(2H-Benzotriazol-2-yl)-4-(l,l,3,3-tetramethylbutyl)-phenol, 311, 326 Cyasorb® UV-3638 2,2'-(l ,4-phenylene)bis(4H-3,l -benzoxazin-4-one, 311 Cyrolite® MBS, 326 Disflamoll® TP Triphenyl phosphate, 246 Doverlube® Stereate based processing aids, 326 Dowfax™ 2A1 Alkyldiphenyloxide disulfonate (Surfactant), 326 Dowlex® (Series) LLDPE, 284 Dowlex® NG 5056E 1-Octene/ethene copolymer (LLDPE), 34, 66 Duraphos® Phosphate ester, 101 Durastrength® 200 I Acrylic impact modifier, 326 Duration™ Stabilized UHMWPE, 101 Dylark® Copolymers of styrene with maleic anhydride, 326 Dyneema® Gel-spun poly(ethylene) fiber in thermoplastic rubber matrix, 34 Eastar® Bio Compostable Copolyester , 205 Elastolit® SR Pólyetherpolyol, 147

352

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Elvax® (Series) Ethylene/vinyl acetate copolymers, 205 Enerpar® Hydraulic oil, 66 Engage™ resins Low density poly(ethylene), 66 Epon® (Series) Diglycidyl ethers of bisphenol A, 326 Escorene® Ultra low density poly(ethylene), 66, 284 Escor® (Series) Ethylene acrylic acid copolymers, 147 Estañe® Poly(ester urethane), 147 Ethanox® 330 l,3,5-Trimethyl-2,4,6-tris(3,5-di-ferf-butyl-4-hydroxybenzyl)benzene, 34 Ethanox® 702 4,4'-Methylenebis(2,6-di-feri-butylphenol), 34 Eval® EP-F Saponified ethylene/vinyl acetate copolymer, 133 Exact® Metallocene catalyzed ethylene copolymers (MCP), 66 Exceed® (Series) Linear low density poly(ethylene), 66 Exxon Bromobutyl™ 2222 Brominated copolymer of isobutylene and isoprene, 178 Exxpro™ Brominated isobutylene p-methylstyrene copolymer, 178 Exxsol® D30 Isoparaffinic hydrocarbon solvents (the number refers to a p p r o x i mate flashpoint in°C), 101 FLEXON™ Paraffinic process oil, 178 Fulcat™ Montorillonit based catalyst, 178 Fyrolflex® RDP Tetraphenyl resorcinol diphosphite, 246, 284 Fyrol® FR-2 Tri(l,3-dichloroisopropyl)phosphate, 284 Geloy® resin ASA copolymer, 344 Glissopal® 1000 Poly(isobutene), 178

Index

353

Glycolube® (Series) Fatty esters, flow promotor, mold release agent, 66 GUR® (Series) UHMWPE, 101 Hefty® Packages, 66 Hercoprime® Maleic-anhydride-grafted PP, 246 Hi-Sil® SBG Precipitated silica, 101 Hitacol Poly(sulfide), 34 Hostaflam® Ammoniumpolyphosphat (flame retardant), 284 Hostavin® UV absorber, 284 HPA™ X Heavy poiyamine , 178 Hytrel® Poly (ester) elastomer, 147 Igepal® Alkylphenoxypoly(ethylenoxy)ethanol, 178 Igepal® CO-210 Nonylphenol ethoxylates, 102 Igepal® CO-630 Nonylphenol ethoxylates, 102 Igepal® RC-630 Dodecylphenol ethoxylates, 102 Iotek® Ionomer, 147 Irgacure® 184 1-Hydroxycyclohexylphenylketone (photo initiator), 326 Irgacure® 2959 l-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-l-propane-l-one, Photoinitiator, 326 Irgacure® 819 2,2-Dimethoxy-2-phenyl acetophenone, 66, 326 Bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide, 66 Irgafos® 168 Tris(2,4-di-terf-butylphenyl)phosphite, 34, 284 Irganox® (Series) Hindered phenols, polymerization inhibitor, 102

354

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Irganox® 1010 Pentaerythritol tetrakis(3-(3,5-di-ferf-butyl-4-hydroxyphenyl)propionate), phenolic antioxidant, 34, 178 Irganox® 1076 Octadecyl-3-(3',5'-di-ferf-butyl-4'-hydroxyphenyl) propionate, 34 Irganox® L57 Octylated/butylated diphenylamine, 178 Irgastab® FS-042 hydrogenated tallow aminé, 284 Irgastat™ P18 Poly(ether-b-amide (antistatic agent), 311, 327 Isopar® G Isoparaffinic solvent, 102, 205 JSR BR-01 c¿s-l,4-Poly(butadiene), 34 KADOX™ 930C Zinc oxide, curing agent, 178 Kane® Ace MBS, 327 Kaydol® oil Mineral oil, 102 Kemester® 1000 G Glycerol trioleate, 102 Kevlar® Aramid, 34, 66 Kraton® Styrenic block copolymer, 147 Lexan® Poly(carbonate), 311, 327, 344 Lubrizol® 2403 2-acrylamido-2-methylpropane sulfonic acid, 205 Lucalen® A 3110 MX polyethylene/acrylic acid/acrylate, 311 Lucentite™ Organophilic clay, 102 Lucryl® Methacrylate copolymer, 311 Lupersol® 331 1,1 -Di-(terf-butylperoxy)cyclohexane, 284 Lupersol® 531 l,l-Di-(terf-amylperoxy)cyclohexane), 284 Lupersol® TAEC 0,0-ferf-Amyl-0-(2-ethylbexyl monoperoxy carbonate), 284

Index

355

Lupersol® TBEC 0,0-ferf-Butyl-0-(2-ethylhexyl)monoperoxy carbonate, 284 Lupersol® TBIC Ο,Ο-fÉTf-Butyl-O-isopropyl monoperoxy carbonate, 284 Lupolen® (Series) Poly(ethylene), 311,344 Lustran® ABS copolymer, 246, 344 Makroion® Poly(carbonate), 246, 327 Marlex® BHB 5003 Metallocene catalyzed ethylene copolymers (MCP), 102 Melapur® 200 Melamine polyphosphate, 285 Melapur® 46 Melamine phosphate, 285 Merlon® Poly(carbonate), 327 Metablen® C Butadiene based rubber (impact modifier), 327 Miranol® Alkylaspartic acid, ampholytic detergent, 102 Mirataine® CBS Coco betaine sultaine, 102 Mirataine® COB Coco oleamidopropyl betaine, 102 Mylar® (Series) Polyethylene terephtalate), 102, 327 Natsyn™ 2200 Poly(isoprene), 178 Naugalube® 640 Octylated, butylated diphenylamine antioxidant, 178 Naugard® XL-1 N,N'-Bis[2-(3-[3,5-di-ferf-butyl-4-hydroxyphenyl]propionyloxy)ethyl]oxamide, 34, 285 Neustrene® 059 Hydrogenated tallow glycerol (30% palmitic, 60% stearic), 102 Neustrene® 064 Hydrogenated tallow glycerol (88% stearic, 10% palmitic), 102 Novodur® ABS, 246 Nuclepore® Laminate membrane, 133

356

Engineering Thermoplastics:

Polyolefins

and

Nuto® H Anti-wear hydraulic oils, 66 Nyglos® Wollastonite, 246 Panipol® EB Poly(aniline), 311, 327 Paraloid® Acrylate rubber, impact modifier, 327 PB® 370 tris[3-Bromo-2,2-bis(bromomethyl)propyl] phosphate, 285 Pebax® Poly(amide imide) (antistatic agent), 147, 246, 327 Pelestat® (Series) Poly(ether amide) (antistatic agent), 311, 327 Pervap® Pervaporation membrane, PVA, Silicone, 246 Petrac® CZ81 Lubricant, 102 Plas-Chek™ 775 Epoxidized soybean oil, 327 Polyblak® 1850 A. Schulman, Inc., 102 Polyoxyter® Processing aid, 327 Primacor® (Series) Ethylene acrylic acid copolymers, 147 Printex® Carbon black, 311 Prism® Poly(urethane) RIM resins, 147 Profax® Poly(propylene), 285 Resiflow® P-67 Poly(acrylic ester) based flow modifier, 327 Retrol® Acid-activated clay, 178 Rhodacal® DS10 Surfactant, 205 Rhodacal® N Sodium napthalene sulfonate, 102 Rhodafac® LO-11A Phosphate ester, 103

Styrenics

Index Rhodameen® (Series) Ethoxylated tallow amine, 103 Rhodapex® CD-128 Ammonium caprylether sulfate, 103 Rhodapon® BOS Sodium 2-ethylhexyl sulfate, 103 Rhodapon® ÜB Sodium lauryl sulfate, 103 Rhodaquat® DAET-90 Quaternary Amine Complex ditallow sulfate , 103 Rhodasurf® LA-12 Linear alcohol ethoxylates, 103 Rhodasurf® LA-3 Linear alcohol ethoxylates, 103 Rhonotec® 201 Antioxidant, 103 Riblene® FF 29 LDPE pellets, 34 Sanduvor® Hindered amine light stabilizer, 285 Santoflex® 13 N-(l,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine, antioxidant, 178 Saytex® 102E Decabromodiphenyl oxide, 285 Saytex® BN-451 Ethylene bis-(dibromo-norbornanedicarboximide), 285 Saytex® BT-93 Ethylene bis-(tetrabromophthalimide), 285 Saytex® RB 100 Tetrabromobisphenol A, 285 Shellflex® 371 Processing oil, 103 Silde-Rite® Closure Systems, 66 Silres® SY 300 Silanol-functional solid phenyl propyl polysiloxane, 246 Spectrim® (Series) Poly(urethane) RIM resins, 147 Stereon® SB copolymer, 327 Styron® 484 Poly(styrene), 285

358

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Sucralose® Chlorodeoxysucrose derívate, artificial sweetener, 178 Sundex™ Rubber processing aid , aromatic oil, 179 Supragil™ WP Dispersant, 103 Surlyn® Ionomer resin, 66, 147, 205 Sylopol® 5910 Catalyst support, 103 Sylvares® ZT105LT Styrene modified terpene resin, 67 Tafmer® Ethylene/a-olefin copolymers (LLDPE), 67 Taktene® 550 T Butadiene rubber, 285 Teflon® Tetrafluoro polymer, 67, 133, 246 Teflon® 30 N PTFE emulsions, 246 Texin® (Series) Thermoplastic poly(urethane), 147 Tinuvin® 120 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, 285 Tinuvin® 144 Bis(l,2,2,6,6-pentamethyl-4-piperidinyl) butyl(3,5-di-terf-butyl-4-hydroxybenzyl)malonate, UV absorber, 34 Tinuvin® 234 2-(2-hydroxy-3,5-di-a-cumylphenyl)-2H-benzotriazole, 285 Tinuvin® 327 2,4-Di-ferf-butyl-6-(5-chloro-2H-benzotriazol-2-yl)phenol, UV absorber, 34, 285 Tinuvin® 328 2-(2'-Hydroxy-3',5'-di-ferf-amylphenyl)benzotriazole, UV absorber, 35, 286 Tinuvin® 928 2-(2-Hydroxy-3-a-cumyl-5-tert-octylphenyl)-2H-benzotriazole, 286 Tinuvin® P 2-(2'-Hydroxy-5'-methylphenyl)benzotriazole, UV absorber, 35 TiPure® R103 Titanium dioxide, 103 Topas® COC Cyclic olefin copolymers, 67

Index TPX® RT-18 4-Methyl-l-pentene polymer, 133 Trigonox® 17 N-butyl-4,4-di(rerf-butylperoxy)valerate, 286 Tufflo® 6056 Mineral oil, 103 Twaron® Aramid, 35 Tyril® ABS copolymer, 344 Ultramid® (Series) Poly(amide), 311 Ultravis® Poly(butene) based additives, 179 Ultrene® Dicyclopentadiene, 35 Uracros® ZW 3307 Divinyl ether resin, 327 Uvasil® (Series) Silane based stabilizers, 286 Uva sorb® UV stabilizers, 286 Uvinul® 3030 l,3-Bis[(2-cyano-3,3-diphenylacryloyI)oxy]-2,2-bis[[(2-cyano-3,3-diphenyl-acryloyl)oxy]methyl]propane (UV absorber), 311, 327 Vector® Styrenic block copolymer, 67 Vectra® (Series) Liquid Crystal Polymer, composed from mainly 4-hydroxybenzoic acid or 6-hydroxy-2-naphthoic acid, further, depending on type: p-acetaminophenol, terephthalic acid, and biphenol, 67 Viaktin® 3890 Acrylourethane resin, 327 Vinaco® 884 Poly(vinyl acetate), 205 Viron-200 Polyester, 35 Vistalon™ 7800 Poly(olefin), 179 Viton® (Series) Fluoropolymer, 179 Vynathene® EVA Copolymers, 205

359

360

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Wingstay® SN-1 (3,6,9-Trioxaundecyl)bis(dodecylthio)propionate, antioxidant for the vulcanization of rubber, 35 Wolkron® Wollastonite, 246 Zeonor® (Series) Cyclo-olefin copolymer, 67 Zeosil® Silica, 179 Zylon® Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber, 35

Acronyms AA Acrylic acid, 194 ABS Acrylonitrile-butadiene-styrene, 211, 270, 315, 331 ADMET Acyclic diene metathesis, 23 AN Acrylonitrile, 212, 298 ASA Acrylonitrile-styrene-acrylate, 331 ATRP Atom transfer radical polymerization, 7 BDP Bisphenol A bis(diphenyl phosphate), 229 CNT Carbon nanorube, 131, 222 COC Cyclic olefin copolymer, 41 CSP Chiral stationary phases, 31 CVD Chemical vapor deposition, 89 DCPD Dicyclopentadiene, 41 DLC Diamond-like carbon, 88 DNBDE Dinorbornenyl dicarboxylate ester, 19 DVD Digital versatile disc, 54 EL Electroluminescence, 54 EVA Ethylene vinyl acetate, 187 EVOH Ethylene vinyl alcohol, 195 FDM Fused deposition modelling, 235 FTIR Fourier transform infrared spectroscopy, 229

362

Engineering Thermoplastics:

Polyolefins

and

GC Gas chromatography, 228, 286 GMA Glycidyl methacrylate, 227, 340 HDPE High density poly(ethylene), 52, 282 HIPS High impact poly(styrene), 222, 269 IC Integrated circuit, 237 LCD Liquid crystalline display, 53 LDPE Low density poly(ethylene), 59, 123, 146 LOI Limiting oxygen index, 233 MA Maleic anhydride, 158, 221, 300, 321 MMA Methyl methacrylate, 315 MMASAN Methyl methacrylate-styrene-acrylonitrile terpolymer, 336 MMBS Methyl methacrylate-butadiene-styrene, 315 MS Mass spectroscopy, 228, 286 PA Poly(amide), 121, 144, 221, 288 PBT Poly(butylene terephthalate), 224, 337 PC Poly(carbonate), 26, 122, 221, 282, 306, 315 PDMS Poly(dimethyl siloxane), 307 PE Poly(ethylene), 29, 61, 75, 116, 138, 190 PES Poly(ethersulfone), 238 PET Polyethylene terephthalate), 61, 119, 224, 290 PIB Poly(isobutylene), 151

Styrentcs

Index PLLA Poly(Mactide), 223 PMMA Poly(methyl methacrylate), 52, 127, 304, 335 PP Poly(propylene), 29, 52, 116, 221, 288 PS Poly(styrene), 61, 236, 269 PTFE Poly(tetrafluoroethylene), 50, 309 PTMO Poly(tetramethylene oxide), 159 PTT Poly(trimethylene terephthalate), 224 PU Poly(urethane), 225, 281 PVA Poly (vinyl alcohol), 193, 239 PVC Poly(vinyl chloride), 236, 288, 315, 341 PVD Physical vapor deposition, 89 RIM Reactive injection molding, 17 ROMP Ring opening metathesis polymerization, 1, 41 SAN Styrene acrylonitrile copolymer, 223, 297, 333 SBR Styrene-butadiene rubber, 270 SPE Solid phase extraction, 30 THF Tetrahydrofuran, 251 TPU Thermoplastic poly(urethane), 159 TPX Poly(4-methyl-l-pentene), 109 TSAN Teflon encapsualed in styrene acrylonitrile copolymer, 309 UHMWPE Ultra high molecular weight poly(ethylene), 75

364

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Chemicals Acetic acid, 189, 240, 288 Acetone, 212 Acetonitrile, 17 Acetophenone, 286 5-Acetoxy-bicyclo[2.2.1]heptene-2, 6 Acetylene, 9 Acetylene black, 145 Acrolein, 332 Acrylamide, 188, 190, 193, 226 Acrylamidobutyraldehyde, 190 Acrylamidoglycolic acid, 191 2-Acrylamido-2-methylpropane sulfonic acid, 194 Acrylic acid, 110, 137, 140, 146, 188, 214, 226, 282, 332 Acrylonitrile, 188, 211, 214, 215, 217, 218, 222, 238, 254, 331, 332, 334 Adipic acid, 198 Allyl acrylate, 332 Allyl alcohol, 63, 332 Allyl bromide, 25 Allyl glycidyl ether, 63 4-Allyl-2-hydroxyphenyl-phenyl-methanone, 24 Allyl methacrylate, 331, 332, 335, 340 Allyl sulfonic acid, 188 Aluminum, 96 Aluminum oxide, 30 Aluminum silicate, 317 p-Aminodiphenylamine, 171 Ammonium bicarbonate, 29 Ammonium nitrate, 173 Ammonium persulfate, 220 Ammonium polyphosphate, 232-234 Amyl acetate, 338 Aniline, 305 4-Anilinophenyl-4-vinylbenzyl ether, 171 4-Anilino-N-(4-vinylbenzyl)aniline, 171 Anthracene, 226 Antimony bromide, 255, 292 Antimony trioxide, 166, 276, 279 Ascorbic acid, 166 Ascorbic palmitate, 271 4,4'-Azobis(4-cyanovaleric acid), 220 Azobisformamide, 196

Index

365

2,2'-Azobis(4-methoxy-2,4-dimethyl valeronitrile), 190 2,2'-Azobis(2-methylbutyronitrile), 220 2,2'-Azobis[2-methyl-N-(2-hydroxyethyl) propionamide], 275 Azodicarbonamide, 196 Barium hydroxide, 198 Behenyl alcohol, 28 Benzaldehyde, 31, 286, 287 Benzonitrile, 16, 17 Benzophenone, 226 4-Benzotriazol-2-ylbenzene-l ,3-diol, 25 3-[5-(Benzotriazol-2-yl)-3-ferf-butyl-4-hydroxyphenyl]-propionic acid, 25 2-Benzotriazol-2-yl-4-methylphenol, 25 Benzoylresorcinol, 234 Benzylidene (l,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)ruthenium dichloride, 50 enrfo-ris-Bicyclo[2,2,l]hept-5-ene-2,3-dicarboxylic acid, 110 (4-(Bicyclo[2.2.1]hept-5-en-2-ylmethoxy)-2-hydroxyphenyl)phenyl-methanone, 24 Bicydo[2.2.1]hept-2-en-5-ylmethyldichlorosilane, 32 Biphenol, 307 5-(4-Biphenylcarbonyloxy)bicyclo[2.2.1 ]hept-2-ene, 26 4-[4,6-Bis-(biphenyl-4-yl)-l,3,5-triazin-2-yl]-benzene-l,3-diol, 25 1,3-Bis(2-chloro-2-propyl)-5-f erf-butylbenzene, 159 Bis(2-ethylene)phthalate, 97 N,N'-Bis(methoxycarbonylbenzoyl)-l,4-butanediamine, 341 2,2-Bis(2-oxolanyl)propane, 274 l,2-Bis(pentabromophenyl)ethane, 166, 278 1,2-Bis(pentabromophenyl)oxide, 278 Bisphenol A, 221, 224, 342 Bisphenol A bis(diphenyl phosphate, 232 1,2-Bis(tribromophenoxy)ethane, 232 Bis-(tricyclopentylphosphine)-dichloro(3-methyl-2-butenylidene) ruthenium, 25 Boron trichloride, 159 Boron trifluoride, 154 Bromoacetyl bromide, 275 Bromobenzene, 116 8-Bromooctene, 10 1,3-Butadiene, 211, 213, 214, 238, 252, 270, 272, 316, 336 n-Butane, 154 Butanediol, 198 ierf-Butanol, 8 Butyl acrylate, 214

366

Engineering

Thermoplastics:

Polyolefins

and

Styrenics

«-Butyl acrylate, 194, 331 ferf-Butyl acrylate, 156 H-Butylamine, 226 Butyl benzyl phthalate, 97 3-[3-ferf-Butyl-5-(5-chlorobenzotriazol-2-yl)-4-hydroxyphenyl]-propionic acid, 25 Butylène dimethacrylate, 316, 317 ferf-Butyl 2-ethylhexyl monoperoxy carbonate, 216, 218 ferf-Butyl hydroperoxide, 192, 220, 334 Butyllithium, 176 N-Butyl-3,6-methylene-l ,2,3,6-tetrahydro-as-phthalimide, 6 ferf-Butyl peracetate, 271 ferf-Butyl perbenzoate, 216, 217 ferf-Butyl peroctoate, 216, 217 ferf-Butyl peroxy isononoate, 216, 218 ferf-Butyl peroxy isopropyl carbonate, 216, 217 ferf-Butyl peroxyneodecanoate, 216, 218 ferf-Butyl phenol, 5 p-ferf-Butylstyrene, 130, 213 Butyric acid, 338 Calcium carbonate, 129, 175, 198, 280 Calcium chloride, 249, 289 Calcium hydroxide, 198 Calcium oxide, 198 Calcium phosphate, 198 Calcium stéarate, 82 Carbon dioxide, 90, 165, 202, 239, 301 Carnauba wax, 56 Chitosan, 238 Chlorobenzene, 4, 116 l-Chloro-l,3-butadiene, 214 2-Chloro-l,3-butadiene, 214 5-Chloromethyl-bicyclo[2.2.1]heptene-2, 6 p-Chloromethylstyrene, 171 o-Chlorostyrene, 214 2-Chloro-2,4,4-trimethylpentane, 154 Citraconic acid, 110 Crotonic acid, 110, 188, 226 (r/ 3 -Crotyl)(cycloocta-l,5-diene)palladium hexafluorophosphate, 49 Cumene, 255, 292 Cumene hydroperoxide, 115, 220, 317 5-Cyano-5-methyl-bicyclo[2.2.1]heptene-2, 6

Index

367

Cyclobutylidene(l-í; 5 -cyclopentadienyl)(l-ry 5 -indenyl) zirconium dichloride, 46 Cycloheptylidene(l-f; 5 -cyclopentadienyl)(l-r/ 5 -indenyl) zirconium dichloride, 46 Cyclohexane, 20, 116, 167 Cyclohexanone peroxide, 115 Cyclohexene, 5, 127 Cyclohexylidene(l-r/ 5 -cyclopentadienyl)(l-r7 5 -indenyl) zirconium dichloride, 46 1,5-Cyclooctadiene, 2, 6 Cyclopentadiene, 18-20, 25, 67 Cyclopentene, 2, 4, 8, 9, 26, 35 Cyclopentylidene(l-J7 5 -cyclopentadienyl)(l-ry 5 -indenyl) zirconium dichloride, 46 Cymene, 9 Decabromodiphenyl oxide, 166, 232, 278 Decahydronaphthalene, 82 Decylphenothiazine, 168 Dibenzoyl peroxide, 115, 271 2,5-Di-ferf-butyl-p-cresol, 272 3,5-Di-terf-butylhydroxyanisole, 50 Dibutylhydroxytoluene, 166 Dibutyimagnesium, 79 Di-terf-butyl peroxide, 50, 115, 220 1,1-Di-ferf-butylperoxycyclohexane, 216 Di-(4-ferf-butylphenyl)iodonium-10-camphor, 58 Dibutyl phthalate, 97 o-Dichlorobenzene, 5, 116 5,5-Dichloro-bicyclo[2.2.1]heptene-2, 6 1,2-Dichloroethane, 6 1,1-Dichloro-fluoroethane, 281 Dichloromethane, 30, 228, 242 l,l-Dichloro-2,2,2-trifluoroethane, 281 Dicumyl peroxide, 49, 63, 115, 126, 192, 226 Dicyclohexyl percarbonate, 220 Dicyclohexyl phthalate, 97 Dicyclopentadiene, 2, 15, 19, 22, 25, 42 4-[4,6-Di-(2,4-dihydroxyphenyl)-l,3,5-triazin-2-yl]-benzene-l,3-diol, 25 2,3-Diethoxycarbonyl-bicyclo[2.2.1 ]hepta-2,5-diene, 6 1 >■.-·!,vl

. . . . I.,I

l>. I

D i o t H y l a K i m i n u m c h l o r i d o , ft, 111

Diethylamine, 5 N,N-Diethyl-bicyclo[2.2.1 ]heptene-2-carbonamide, 6

368

Engineering

Thermoplastics:

Polyolefins

and

Styrenics

Diethylhexyl phthalate, 305 Dihydrodicyclopentadienyl acrylate, 331 l,4-Dihydro-l,4-methanonaphthalene, 2, 6 Dihydroxy aluminum sodium carbonate, 82 2,4-Dihydroxybenzophenone, 25 (2,4-Dihydroxyphenyl)-phenylmethanone, 25 Diisodecyl phthalate, 97 Diisopropylbenzene hydroperoxide, 220 Diisopropyl ether, 62 Diisopropyl peroxide, 115 (1,3-Diisopropyltetrahydropyrimidin-2-ylidene) (ethoxymethylene) (tricyclohexylphosphine) ruthenium dichloride, 46 Dilauryl thiodipropionate, 320 5,6-Dimethoxycarbonyl-bicyclo[2.2.1]heptene-2, 6 Dimethyl acetal, 190 Dimethylanilinium tetrakis(pentafluorophenylborate), 50 Ν,Ν-Dimethylanilinium tetrakis-perfluorophenylboron, 46 2,5-Dimethyl-2,5-di-f erf-butylperoxy-hexyne-3, 115 Dimethyldichlorosilane, 176 2,4-Dimethylstyrene, 214 2,5-Dimethylstyrene, 213 2,4-Dinitrilebut-l-ene, 254 2,6-Dinitrile-4-phenylhex-l-ene, 254 4,6-Dinitrile-2-phenylhex-l-ene, 254 Dinitrobenzoylphenylalanine, 31 Dinitroso-pentamethylene-tetramine, 192 Dioctyl phthalate, 338 Dioxan, 171 2,4-Diphenylbut-l-ene, 254, 287 Diphenyl carbonate, 225 Diphenyl chlorophosphate, 235 Diphenyl cresyl phosphate, 232 3,3-Diphenylcyclopropene, 9 (Diphenyldichlorosilane, 235 Diphenyl-2-ethyl cresyl phosphate, 232 Diphenylmethylene(cyclopentadienyl) (9-fluorenyl) zirconium dichloride, 46 Diphenylmethylidene(cyclopentadienyl)(9-fluorenyl) zirconium dichloride, 46 Diphenyl oxide sulfonate, 317 Ο,Ο-Diphenyl-N-phenylphosphoramidate, 232 4-(4,6-Diphenyl)-l,3,5-triazin-2-yl-benzene-l,3-diol, 25 Ditridecyl phthalate, 97

Index Divinylbenzene, 50, 151, 297, 316, 317 Dodecylenedinorbornene dicarboxyimide, 2 Dodecylmercaptan, 218, 219, 272, 335 1-Eicosene, 110 ß-(3,4-Epoxy cyclohexyl) ethyl trimethoxysilane, 233 Ethanol, 4, 75, 202 Ethyl acetate, 19, 305, 338 Ethyl acrylate, 194, 214 Ethylaluminum dichloride, 154 Ethylaluminum sesquichloride, 19 Ethylbenzene, 116, 211, 217, 254, 272, 300, 301 Ethyl cellulose, 121, 239 Ethylene bis(indenyl) zirconium dichloride, 45, 46 Ethylene bistetrabromophthalimide, 166 Ethylene diamine, 170 Ethylene glycol dimethacrylate, 335 Ethylene sulfonic acid, 188 2-Ethylhexyl acrylate, 2, 194, 214 5-Ethylidene-2-norbornene, 42 Ethyl lactate, 58 2-Ethyl methacrylate phosphoric acid, 195 N'-2-Ethylphenyl-N'-2-hydroxyphenyloxalamide, 25 o-Ethylstyrene, 214 m-Ethylstyrene, 214 p-Ethylstyrene, 214 Ethyltetracyclododecene, 42, 62 Ethyltriphenyl phosphonium bromide, 223 Ferrocenealdehyde, 31 Fumaric acid, 110, 137, 138 Fumaronitrile, 211, 212 Glutaraldehyde, 238 Guerbet ester, 97 Hafnium tetrakis(trimethylsilylmethyl), 78 n-Heptane, 112 Hexabromocyclododecane, 166 1-Hexadecene, 110 l,4,4a,5,8,8a-Hexahydro-l,4,5,8-dimethanonaphthalene, 30 Hexamethylcyclotrisiloxane, 176 Hexamethyldisilazane, 79 Hexamethylenetetramine, 323 5,5,5',5',5",5"-Hexamethyl tris(l,3,2-dioxaphosphorinane-methane)amino-2,2',2"-trioxide, 232 1-Hexene, 17, 25, 78, 111, 114, 137, 138

369

370

Engineering Thermoplastics:

Polyolefins

and

Styrenics

Hydrotalcite, 82 Hydroxyacetone, 271 p-Hydroxydiphenylamine, 171 2-Hydroxyethyl acrylate, 20 2-Hydroxy-2-phenylacetophenone, 271 Hydroxypropyl methacrylate, 340 Isobutane, 79, 154 Isobutylene, 153, 154, 156, 157, 203 Isobutylmethylol acrylamide, 191 Isobutyl vinyl ether, 153 Isoprenylaluminum, 77 Isopropylene bis(l-indenyl) zirconium dichloride, 47 4-Isopropyltoluene), 9 Itaconic acid, 110, 137, 138, 188 Kaolin, 118 Lauroyl peroxide, 115 R-Limonene, 289 Magnesium hydroxide, 278, 279 Magnesium hypochlorite, 161 Magnesium oxide, 198 Maleic acid, 49, 110, 137, 138, 188 Maleic anhydride, 48, 56, 63, 137, 250 Mesityl imidazole, 10 l-Mesityl-3-(7-octene)-imidazole bromide, 10 Methacrylic acid, 110, 137, 138, 146, 188, 214, 332 Methacrylonitrile, 214 3-(Methacryloxy)propyltrimethoxysilane, 279 Methanol, 14, 112, 153, 190, 195, 202, 289, 300 5-Methoxymethylbicyclo[2.2.1]heptene-2, 6 Methyl acetate, 195 Methyl acrylamidoglycolate methyl ether, 191 α-Methylbenzenaldehyde, 286 Methylcyclopentane, 116 2-Methyl-l,4,5,8-dimethano-l,2,3,4,4a,5,8,8a-octahydronaphthalene, 41 Methylene-bis(3-t-butyl-l-indenyl)hafnium dichloride, 46 Methylene-bis(3-ferf-butyl-l-indenyl) zirconium dichloride, 46 Méthylène chloride, 4 3,6-Methylene-l,2,3,6-tetrahydro-ris-phthalic anhydride, 6 4-(l-Methyl-l-ethylidene)-l-methyl-l-cyclohexene, 272 Methyl ethyl ketone, 217 Methyl ethyl ketone peroxide, 115 Methyl methacrylate, 211, 213, 269, 316, 317, 331, 336 5-Methyl-2-norbornene, 42

N-Methylol acrylamide, 188, 190, 191, 194 4-Methyl-l-pentene, 42, 109-112, 114, 117, 119, 129 2-Methyl-pentylalumoxane, 46 Methylphosphonic acid diphenyl ester, 232 a-Methylstyrene, 211-214, 219, 270, 272, 297, 301, 302 4-Methylstyrene, 151, 152, 214, 270 m-Methylstyrene, 214 o-Methylstyrene, 213, 214 2-Methyltetracyclododecene-2-carboxylic acid methyl ester, 42 Montmorillonite, 80, 222, 274, 275 Nadie acid, 49 Naphthalene, 255, 292 1-Naphthyl glycidyl ether, 222 Nickel acetylacetonate, 2 Nickel bis-(tri-n-butylphosphine) dichloride, 2 Nickel bis-(tricyclohexylphosphine) dichloride, 2 Nickel(2-ethylhexanoate), 49 2-Nitrile-4,6-diphenylhex-l-ene, 254 4-Nitrile-2,6-diphenylhex-l-ene, 254 2-Nitrile-4-phenylbut-l-ene, 254 Nonylphenol, 334 Norbornadiene, 2, 43 2-Norbornene, 50, 67 Norbornene carboxylic acid butyl ester, 50 Norborn-5-ene-2,3-dicarboxylic anhydride, 30 Norbornene 2-ethylhexyl carboxylate, 2, 20 cndo-Norbornene-5-yl-N,N-di-2-pyridyl carboxylic amide, 31 Nucleosil, 31 1-Octadecene, 110 7-Oxabicyclo[2.2.1]hept-5-ene-2-carboxylic acid, 32 p,p'-Oxybis(benzenesulfonyl hydrazide), 192 Paclitaxel, 175 Palladium(II) acetylacetonate, 50 Pentaerythritol bis(methyl phosphate), 233 Pentaerythritol bis(phenyl phosphate), 232, 233 Pentaerythritol diphenyl diphosphate, 233 Pentaerythritol distearate, 57 Pentaerythritol tetrastearate, 57 Pentafluoroethane, 120 n-Pentane, 10 Phenol, 212 Phenylacetylene, 25 nz-Phenylene-bis(diphenyl phosphate), 232

372

Engineering Thermoplastics:

Polyolefins

and

Styrenics

1,3-Phenylene-N,N'-bis(0,0-diphenylphosphoramidate), 232 Phenylenediamine, 291 p-Phenylene diamine, 171 N-Phenylmaleimide, 211, 213 Phenylmethylene-bis-(tricyclohexylphosphine) ruthenium dichloride, 22 N-Phenyl-3,6-methylene-l ,2,3,6-tetrahydro-cis-phthalimide, 6 2-Phenyl-4-nitrilebut-l-ene, 254 N-Phenyl-7-oxabicyclo[2.2.1]5-heptene-2,3-dicarboximide, 32 Phenyl phosphonic acid diethyl ester, 232 4-Phenylstyrene, 213 Phosphonium sulfonate, 283 Phosphorus oxychloride, 235 Phosphorus pentachloride, 5 Phthalic anhydride, 112 Piperazinediy]-N,N'-bis(0,0-diphenylphosphorarnidate, 232 Piperylene, 214 Potassium tert-butylate, 158 Potassium hypochlorite, 161 Potassium hypophosphite, 318 Potassium peroxydisulfate, 298 Potassium perphosphate, 220 Potassium persulfate, 220, 334, 335 Propylamine, 17 exo,m)-N,N'-Propylene-di-(norbornene-5,6-dicarboxyimide, 2 Propyl gállate, 166 Pyridine, 14 5-(2-Pyridyl)-bicyclo[2.2.1]heptene-2, 6 Quebracho, 249, 289 8-Quinolinoxytitanium trichloride, 79 5-(4-Quinolyl)-bicyclo[2.2.1]heptene-2, 6 Salicylic acid, 29 Siloxane bischloroformate, 307 Sodium bicarbonate, 29 Sodium diamyl sulfosuccinate, 193 Sodium dicyclohexyl sulfosuccinate, 193 Sodium diisopropylnaphthalene sulfosuccinate, 193 Sodium dodecyl sulfate, 335 Sodium dodecyl sulfonate, 333 Sodium erysorbate, 193 Sodium 2-ethylhexyl sulfate, 193 Sodium formaldehyde sulfoxylate, 317 Sodium hypochlorite, 161 Sodium isobutyl sulfosuccinate, 193

Sodium montmorillonite, 275 Sodium perborate, 220 Sodium persulfate, 192, 220, 333, 334 Sodium phosphate, 318 Sodium sulfosuccinate, 193 Stearyl alcohol, 28 Styrène, 17, 211, 213-215, 270, 297, 315, 316, 331 Styrene-7,8-oxide, 287 Succinic anhydride, 20 Terephthalic acid, 198 Tetraallyl silane, 21 Tetrabromobisphenol A, 323 Tetrachloroethylene, 338 Tetracyclododecene, 41, 42, 50 Tetradecabromodiphenoxybenzene, 166 H-Tetradecane, 242 Tetradecylphenothiazine, 168 1,1,1,2-Tetrafluoroethane, 281 2,2,3,3-Tetramethyl-l,4-dibromobutane, 156 Thiophene, 16, 17 Titanium dioxide, 339 Titanium tetrachloride, 77, 159 Toluene sulfinic acid, 271 p-Toluenesulfonic acid, 20 p-Toluene sulfonyl hydrazide, 192 Tributylamine, 275 Tributyl phosphate, 232 Tributylphosphine, 16, 17 Trichlorodifluoroethane, 117 Trichloroethylene, 127 Trichlorofluoromethane, 117, 308 Tricresyl phosphate, 28, 232 Tricyclohexylphosphine, 9, 14, 15, 50 Tricyclopentylphosphine, 14, 15 5-Triethoxysilyl-2-norbornene, 41, 42 Triethylaluminum, 62, 78, 79, 112 Triethylamine, 226 Triethylborane, 49 Triethylene glycol, 308 a, a, «-Trifluorotoluene, 49 Triisopropylphenyl phosphate, 232 Triisopropylphosphine, 14 Trimethoxyvinylsilane, 63

374

Engineering

Thermoplastics:

Polyolefins

and

Trimethylaluminum, 45 Trimethylamine, 226 Trimethylchlorosilane, 176 Trimethylmethoxysilane, 112 Trimethylolpropane triacrylate, 270 2,4,4-Trimethyl-pentylalumoxane, 46 Triphenylarsine, 17 2,4,6-Triphenylhex-l-ene, 254 Triphenyl phosphate, 229, 232, 233, 278 Triphenyl phosphine, 14 Triphenyl phosphite, 17 Tris-(2-chloroethyl)phosphate, 232 Tris(2,4-di-ferf-butylphenyl)phosphite, 232, 234 l,l,3-Tris(2-methyl-4-hydroxy-5-tert-butyl phenyl)butane, 320 Trixylyl phosphate, 28 Tungsten carbide, 90 Tungsten hexachloride, 19, 62 Versatic acid vinyl ester, 193 Vinyl acetate, 187-189, 193 4-Vinylbiphenyl, 130 4-Vinylcyclohex-l-ene, 318 Vinylidene chloride, 188 5-Vinyl-2-norbornene, 42, 50 N-Vinylpyrrolidone, 188 Xylene, 116, 167 Zinc borate, 229 Zirconium acetylacetonate, 332 Zirconium tetrakis(trimethylsilylmethyl), 78

Styrenics

Index

375

General Index Abrasion resistance, 83, 222 Absorber IR, 28 UV, 24, 25, 306 Absorption organics, 63 sound,83 water, 26, 83 Accident chemical plant, 247 environmental, 179 Accumulation monomers, 287 Acetabular cup, 86 Acoustic devices, 128 Activator blowing agent, 192 polymerization, 22, 46 Additive anti-striation, 58 antioxidant, 166, 319 antistatic, 144 aqueous systems, 321 biodegradable, 198 cement, 237 drag reducer, 167 electrically conducting, 229 flame retardant, 221, 232, 278, 322 for SAN, 306 fuel, 167 gel modification, 14 gel processing, 97 impact modifier, 278 inorganic, 82 low gloss, 308, 339 master batch, 170 mold release, 231 plasticizer, 58 polyolefin, 28

UV-protection, 165 viscosity modifiers, 155 weatherability improver, 339 Adhesion promoters, 188 Adhesives, 59, 63, 125, 146, 166, 176, 198, 201 Adsorbent material, 99, 286 Agglomeration, 76, 191, 218, 219, 318 partial, 219 random, 239 Aging, 343 Aging resistance, 334 Agricultural films, 29 Airplanes, 146 Anode materials, 243 Anti-drip agents, 235, 309 Antimicrobial ASA, 343 Antistatic agents, 28, 144, 282 Arrhenius factor, 253 Artificial hip joints, 85, 86 Aseptic loosening, 86 Autoclave, 6, 193 Azeotropic points, 302 Bacteria, 125, 343 Ball-cup friction, 86 Ballistic vests, 100 Barrier polymers, 303 Barrier properties, 23, 52, 125, 195 Battery separators, 121, 122 Betaines, 97 Biodegradation accelerant, 198 Biofuels, 202 Biostability, 159 Blister packs, 18, 59 Blistering, 281 /3-Blockers, 31 Blow molding, 59, 132, 139 Bone cement, 87 Bottles, 59, 279, 321

376

Engineering Thermoplastics:

Branching agent, 156 Brazing, 89 Butyl rubber, 161, 175, 200 Cage effect, 226 Calendering, 99 Capacitors, 98 Carbocationic polymerization, 168 Carbon nanotubes, 131, 132 Catalysts alumoxane, 46 amine, 225 classification, 8 coated, 189 Friedel-Crafts, 154 hydrodenitrogenation, 255 metallocene, 45-47 metathesis, 7 mixed, 78 organometallic, 43 phase transfer, 307 ROMP, 12 ruthenium, 15 single-site, 76, 79 transition metal, 26 zeolite, 255, 292 Ziegler-Natta, 44, 49, 76, 112 Ceiling temperature, 212 Cements, 237 Ceramics, 96, 128, 248 Chain transfer agent, 24, 44, 111, 218, 219, 272, 300, 335 Chewing gums, 174 Chromatographie supports, 30 Clarity, 57, 59, 197, 319 Clay nanocomposites, 233 Cloud-point pressure, 117 Co-spin agent, 117 Coaxial cables, 28, 29 Coaxial fibers, 204 Cold compaction strength, 82 Cold flow improvers, 203 Colloidal stability, 219 Comb polymer, 203

Polyolefins

and

Styrenics

Compatibilization, 291 Composites ABS, 221, 229 antistatic, 282 carbonnanotubes, 131, 222 CNT reinforced, 227 conductive, 229 fiber reinforced, 21, 50, 88, 310 nano, 232, 274 prosthetic bearings, 87 thermosets, 19 TPU/PIB, 159 weatherable, 336 Compositions, 168 adhesive, 166, 176, 202 antistatic, 222 cementing, 237 chewing gum, 174 conductive, 236 crosslinkable, 41 foam, 236 heat sealable, 123 ionomer, 139 low gloss, 340 lubricating, 170 molding, 47, 221, 336 powder coatings, 324 solar control, 146 thermoset, 19, 50 Concrete, 174, 199 Condensation reaction, 323 Conductivity electrical, 77, 223, 229, 230 thermal, 84 Conformational energy, 162 Contact angle, 51, 231, 239 Cookware, 118 Coronary stent, 175 Cosmetic applications, 120 Coupling agent, 233, 250, 272, 274 Crazing, 276, 281 Crosslinking chemical, 93, 191

Index density, 96 electron beam, 93, 94 inhibitors, 302 ionic, 141, 143 mechanisms, 140 monomers, 190, 238, 270, 317 peroxide, 84, 141 properties, 92, 93, 276 radiation, 270 surface, 93 Cryogenic applications, 84 Crystallization, 131, 143, 163 Cure accelerator, 323 Cushion materials, 191 Cyclization, 10, 156, 254 Dehydration, 75, 239 Dehydrochlorination, 158, 164 Diamond coatings, 88 Dielectric loss, 28, 29, 64 Diels-Alder reaction, 2, 19, 25, 27, 41 Diesel fuel, 202 Digital cameras, 54 Disordered carbon, 243, 244 Drag reduction, 167 Drug delivery, 176, 197, 204 Drug release, 175 Dulling agents, 340 Dust adherence, 61 Dust explosion, 247 Edgebands, 202 Electroless plating, 240 Electrolytes, 121, 122, 144 Electroplating, 240 Emulsion explosives, 173 Encapsulation blowing agent, 300 phase change material, 241 polymer, 309 End-reactive oligomers, 164 polymers, 164 Endcapping reagent, 24, 307

377

Exfoliation, 275 Fatty amines, 97 Fibrillation, 99, 117 Filaments, 236 Fillers, 84, 131, 202, 235 Films adhesive, 64 agricultural, 29 anti-glare, 53 barrier, 59 conductive, 64 fibril strands, 116 optical, 26 overwrap, 125 oxygen scavenging, 62 packaging, 18, 29 polarizing, 18, 54 porous, 121 water-repellent, 201 Fish eyes, 195 Flammability, 83, 189 Flip chip bonding, 64 Floating, 248 Floor tiles, 145 Fluidized-bed reactor, 67 Fluorescence, 55 Foaming agents, 28, 29, 196 Foaming aids, 29 Foams abrasion resistant, 191 microcellular, 117 Food packaging, 29, 118, 120, 144, 287 Foodservice applications, 279 Footwear, 191 Fractionation, 80 Freeze-coagulation, 219 Fresnel lenses, 29 Friedel-Crafts reaction, 211 Froth flotation, 249, 289 Fruits packaging, 124 respiration rates, 124

378

Engineering Thermoplastics:

Fuel additive, 167 Fuel cells, 98, 145 Fuels, 166 Garden furniture, 342 Gel permeation chromatography, 19 Golf balls, 139 Grignard coupling, 156 Headspace solid phase microextraction, 286 Heat aging, 319 Heat resistance, 18, 26, 54, 62, 64, 118, 121, 123-126, 191, 227, 236, 321 High-voltage power cables, 28 Hip joint, 85 Hip replacements, 93 Histiocytic reactions, 86 Hock process, 212 Hot stamping, 81 ß-Hydride elimination, 78 Hydrocyclones, 249, 289 Image forming, 55, 126 Impact resistance, 18, 79, 83, 123, 125, 227, 232, 282 Infusion bags, 18 Inifer method, 164 Initiators functional, 153, 156 ionic, 274 metathesis, 8 peroxides, 19, 215-217, 226, 271 photo, 29 redox, 271 Injection molding, 17, 44, 59, 123, 139, 141, 191, 215, 222, 247, 283, 310, 321, 342 Interactions, 76, 84 Intercalations, 233, 243, 275 Interlayer adhesion, 196 Ion-pair dissociation, 152 Isotactic copolymers, 114 Laminates, 122, 145, 342

Polyolefins

and

Styrenics

Laser beam weldability, 230 Laser printers, 54, 127 Lewis acid, 153, 154 Lithium batteries, 98 Lithium ion batteries, 121, 122, 243 Loop slurry process, 78 Lube oils, 166 Lubricants, 82, 97, 155, 231, 323, 343 Macroinitiators, 7 Macromonomers, 6 Macrophages, 86 Magneto rheological elastomers, 237 Masonry surfaces, 201 Mastics, 200 Media aggressive, 304 charging, 290 data storage, 57 packaging, 124 Membranes, 96, 120 Metal soaps, 82 Metalcarbene complexes, 4 Metallization, 240 Metallocenes, 45 Microcapsules, 242 Microporous battery separators, 98 fibers, 140 membranes, 96 sheets, 98 Microspheres, 173, 300 Microwave crosslinking, 93 extraction, 286 heating, 95 plasma-assisted, 90 radiation, 95 resistance, 118 Miktoarm star polymers, 156 Mold release agent, 231, 306 Mold-releasing materials, 124

Index Monolithic capillary columns, Multilayered film, 59 Municipal waste, 255, 291 Nanocomposites, 274, 275 Nanofiltration, 238 Non-blocking test, 199 Nonwoven fabrics, 121, 122 Novolak, 243, 323 Nucleating agents, i 18, 131 Oil absorbent, 63 Oil-less toners, 56 Optical Applications, 54 Optical lenses, 26 Organophilic clay, 80 Ozone depletion, 117, 281 Particles capsule, 272 carbon, 239 catalyst, 78 filler, 235 gel, 48 grafted, 227 magnetizable, 237 metal hydride, 242 mirco, 192 polymer, 47, 76, 78, 219 rubber, 219, 269, 271, 273, 276, 309, 334 soft phase, 276 toner, 57 wear, 86 Peelability, 119 Pervaporation membranes, 239 Photoacid generators, 58 Photocopiers, 127 Photomask, 57, 58 Photoresists, 57, 58, 62 Photo initiators, 19 Pipelines, 167 Plasticizers, 28, 272 Plexifilamentary fibers, 117 Plexifilaments, 117 Plugging point, 203

379

Plumbing fixtures, 240 Pneumatic transport, 76 Polymerization alkyne, 25 anionic, 7, 272 cationic, 152, 156 continuous bulk, 271 emulsion, 194, 198, 218, 317, 334 free enthalpy, 5 free radical, 215, 299 graft, 219 Grignard coupling, 156, 157 macromonomers, 7 mass, 215 metallocene catalyzed, 47 metathesis, 3 precipitation, 30 quasi living, 44 radical, 114 slurry, 154 solution, 190 suspension, 30, 76 vinyl addition, 44, 48 Ziegler-Natta, 44, 76, 111 Polymers alternating, 299 block, 19 core-shell, 315 crosslinked, 18 cyclic olefin, 10, 41 degradable, 4 elastomers, 165 emulsion, 193 end-reactive, 164 flash spinning, 116 fuel additive, 167 functional, 23 functionalized, 225 graft, 224, 226 hydrophobic, 145 ionic, 137 living, 153 metathesis, 1, 43

380

Engineering Thermoplastics:

popcorn, 302 recycling, 251 regio-regular, 24 ring opening, 17 semicrystalline, 166, 188 star, 155 telechelic, 24 thçrmoset, 19 UHMWPE, 81 unsaturated, 32 water-soluble, 13 Popcorn polymers, 302 Post-crystallization, 60 Prepregs, 322, 324 Pressure sensitive adhesives, 176 Printed circuit, 124 Processing aids, 198, 343 Prosthetic joints, 84 Quenching reagents, 153 Radioactive mineral deposits, 130 Rapid prototyping, 235 Reaction 1,2-addition, 274 backbiting, 163 control agent, 20 disproportionation, 95, 163 transalkylideneation, 3 Recycling, 67, 179, 247, 288, 310 Refractive index, 52, 222, 307 Reinforcement fibers, 21, 88 phase, 21 Reinforcing fibers, 22 fillers, 84, 323 Resilient foams, 191 Reverse osmosis membranes, 238 Rheology modifiers, 155 Ring-chain equilibrium, 5 Safety glass, 145 Sailing boats, 100 Sandals, 191 Sanitary units, 343

Polyolefins

and

Styrenics

Saponification, 195 Satellite antennas, 342 Scavenger acid, 82 chlorine, 81 oxygen, 62, 88 Scintillators, 130 Scratch resistance, 128, 335 Seeded emulsion polymerization, 333 Semiconductor chip, 64 Semiconductors, 61 Shelf-aging, 92 Short circuits, 121, 122 Shutdown separators, 98 Sick house syndrome, 192 Silicon wafers, 58 Sintering, 82, 89 Slurry aids, 111 Smoke suppression, 279 Sol-gel technology, 30 Solar control, 146 Solvent casting, 18 Solvothermal method, 226 Sonochemical reactions, 95 Sound-dampening, 83 Speaker panels, 128 Spin welding, 81 Spinnerette, 140 Sport applications, 197 Stabilizers heat, 218, 231, 232, 343 light, 84, 231, 235, 306, 338 reactive, 301 Staining contaminants, 200 Steam cracking, 75, 211 Sterilization, 81, 88, 92 Stress dissipation, 238 whitening, 281 Stretch-blow molding, 59 Sub-surface fatigue, 86 Sultaines, 97

Index Surface embossing, 340 Surfactants, 97, 155, 193, 221 Synergistic effects flame retardants, 166, 233, 279, 292 optical properties, 336 Tackifier, 146, 166 Tearability, 279 Tissue necrosis, 86 Toner formulations, 56 Toner resins, 29, 55 Transdermal drug delivery, 176 Transesterification, 195, 332 Transparent adhesives, 176 conductive products, 54 products, 18, 309 resins, 26, 119 SAN, 307 Triboelectric separators, 290 Triboelectrification, 249, 289

381

Turbulent flow, 167 Twin-screw extruder, 62, 97, 198, 229, 300 Ultrasonic transducer heads, 120 Vacuum metallization, 240 Vacuum packaging, 92 Vegetables, 124 Video projector, 129 Vulcanization, 4, 141, 151 Water resistance, 18, 26 Water-initiation, 153 Waxes, 201 Wear debris, 86 Weathering, 18, 166, 336, 338, 339, 343 Weatherometer, 230 Welding, 89 Wire coating, 18, 29 Wood-plastic composites, 250 Wurtz-Fittig reaction, 157

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Also of Interest Check out these published and forthcoming related titles from Scrivener Publishing A Concise Introduction to Additives for Thermoplastic Polymers by Johannes Karl Fink. Published 2010. ISBN 978-0-470-60955-2. The book focuses on additives for thermoplastic polymers and describes 21 of the most important and commonly used additives from Plasticizers and Fillers to Optical Brighteners and Anti-Microbial additives. It also includes chapters on safety and hazards, and prediction of service time models. Guide to Safe Material and Chemical Handling by Nicholas P. Cheremisinoff and Anton Davletshin. Published 2010. ISBN 978-0-470-62582-8 The volume provides an assembly of useful engineering and properties data on materials of selection for process equipment, and the chemical properties, including toxicity of industrial solvents and chemicals. Handbook of Engineering and Specialty Thermoplastics Volume Two: Polyethers and Polyesters edited by Sabu Thomas and Visakh P.M. Forthcoming late 2010. Volume Three: Nylons edited by Sabu Thomas and Visakh P.M. Forthcoming late 2010. Volume Four: Water Soluble Polymers edited by Johannes Karl Fink. Forthcoming 2011. Miniemulsion Polymerization Technology edited by Vikas Mittal. Forthcoming summer 2010.

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