PAGE 1 OF 47 PETITIONERS' EXHIBIT 1113

HANDBOOK OF THERMOPLASTICS

EDITED BY OLAGOKE OLABISI

PAGE 2 OF 47

F1' MEADE GenColl

---­TP 1180 .15 H36

',1997 Copy 2

PAGE 3 OF 47

PAGE 4 OF 47

HANDBOOK OF THERMOPLASTICS

PAGE 5 OF 47

PLASTICS ENGINEERING

Founding Editor

Donald E. Hudgin

Professor Clemson University

Clemson, South Carolina

1 . Plastics Waste: Recovery of Economic Value, Jacob Leidner 2. Polyester Molding Compounds, Robert Burns 3. Carbon Black-Polymer Composites: The Physics of Electrically Conducting

Composites, edited by Enid Keil Sichel 4. The Strength and Stiffness of Polymers, edited by Anagnostis E. Zach

ariades and Roger S. Porter 5. Selecting Thermoplastics for Engineering Applications, Charles P. Mac­

Dermott 6. Engineering with Rigid PVC: Processability and Applications, edited by I.

Luis Gomez 7. Computer-Aided Design of Polymers and Composites, D. H. Kaelble 8. Engineering Thermoplastics: Properties and Applications, edited by James M.

Margolis 9. Structural Foam: A Purchasing and Design Guide, Bruce C. Wendle

1 0. Plastics in Architecture: A Guide to Acrylic and Polycarbonate, Ralph Montella

11. Metal-Filled Polymers: Properties and Applications, edited by Swapan K. Bhattacharya

12. Plastics Technology Handbook, Manas Chanda and Sa/if K. Roy 13. Reaction Injection Molding Machinery and Processes, F. Melvin Sweeney 14. Practical Thermoforming: Principles and Applications, John Florian 15. Injection and Compression Molding Fundamentals, edited by Avraam I.

/sayev 16. Polymer Mixing and Extrusion Technology, Nicholas P. Cheremisinoff 17. High Modulus Polymers: Approaches to Design and Development, edited by

Anagnostis E. Zachariades and Roger S. Porter 18. Corrosion-Resistant Plastic Composites in Chemical Plant Design, John H.

Mallinson , 19. Handbook of Elastomers: New Developments and Technology, edited by

Ani/ K. Bhowmick and Howard L. Stephens 20. Rubber Compounding: Principles, Materials, and Techniques, Fred \1\1.

Barlow 21 . Thermoplastic Polymer Additives: Theory and Practice, edited by John T.

Lutz, Jr. 22. · Emulsion Polymer Technology, Robert D. Athey, Jr. 23. · Mixing in Polymer Processing, edited by Chris Rauwendaa/

PAGE 6 OF 47

24. Handbook of Polymer Synthesis, Parts A and B, edited by Hans R. Kricheldort

25. Computational Modeling of Polymers, edited by Jozef Bicerano 26. Plastics Technology Handbook: Second Edition, Revised and Expanded,

Manas Chanda and Sa/if K. Roy 27. Prediction of Polymer Properties, Jozef Bicerano 28. Ferroelectric Polymers: Chemistry, Physics, and Applications, edited by

Hari Singh Nalwa 29. Degradable Polymers, Recycling, and Plastics Waste Management, edited

by Ann-Christine Albertsson and Samuel J. Huang 30. Polymer Toughening, edited by Charles B. Arends 31. Handbook of Applied Polymer Processing Technology, edited by Nicholas P.

Cheremisinoff and Paul N. Cheremisinoff 32. Diffusion in Polymers, edited by P. Neogi 33. Polymer Devolatilization, edited by Ramon J. Albalak 34. Anionic Polymerization: Principles and Practical Applications, Henry L. Hsieh and

Roderic P. Quirk 35. Cationic Polymerizations: Mechanisms, Synthesis/ and Applications, edited by

Krzysztof Matyjaszewski 36. Polyimides: Fundamentals and Applications, edited by Malay K. Ghosh and K. L.

Mittal 3 7. Thermoplastic Melt Rheology and Processing, A. V. Shenoy and D. R. Saini 38. Prediction of Polymer Properties: Second Edition, Revised and Expanded, Jozef

Bicerano 39. Practical Thermoforming: Principles and Applications, Second Edition, Revised

and Expanded, John Florian 40. Macromolecular Design of Polymeric Materials, edited by Koichi Hatada, Tatsuki

Kitayama, and Otto Vogl 41. Handbook of Thermoplastics, edited by Olagoke Olabisi 42. Selecting Thermoplastics for Engineering Applications: Second Edition, Revised

and Expanded, Charles P. MacDermott and Aroon V. Shenoy

Additional Volumes in Preparation

\

PAGE 7 OF 47

HANDBOOK OF H_

THERMOPLASTICS

EDITED BY

OlAGOKE OlABISI King Fahd University of Petroleum and Minerals Dhahran, Saudi Arabia

MARCEL DEKKER, INc. NEw YoRK • BASEL • HoNG KoNG

PAGE 8 OF 47

Library of Congress Cataloging-in-Publication Data

Handbook of thermoplastics I edited by Olagoke Olabisi. p. em.- (Plastics engineering; 41)

Includes index. ISBN 0-8247-9797-3 (he : alk. paper) 1. Thermoplastics-Handbooks, manuals, etc. I. Olabisi, Olagoke.

II. Series: Plastics engineering (Marcel Dekker, Inc.) ; 41. TP1180.T5H36 1997 668.4'23-dc21

97-58 . --------CIP

The publisher offers discounts on this book when ordered in bulk quantities. For more information, write to Special Sales/Professional Marketing at the address below.

This book is printed on acid-free paper.

Copyright© 1997 by MARCEL DEKKER, INC. All Rights Reserved.

Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher.

MARCEL DEKKER, INC. 270 Madison Avenue, New York, New York 10016

Current printing (last digit): 10 9 8 7 6 5 4 3 2 1

PRINTED IN THE UNITED STATES OF AMERICA

PAGE 9 OF 47

To the memory of my mother Maria Qlapade Qlabisi

and my father Joseph Qna<;>lap<;> Qlabisi

Ji sun reo

iii

PAGE 10 OF 47

-

Preface

The global thermoplastics market, representing approximately 10% of the worldwide chem­ical industry, is the fastest growing segment of the world economy. This growth is being driven by several forces, among which are the following: (a) the widening sphere as well as the demanding requirements of the emerging thermoplastics applications; (b) the need to conserve the dwindling natural resources and the environment; (c) competitive basic, mission-oriented, and applied R&D (corporate, national, or international); and (d) the rev­olutionary and evolutionary scientific and technological innovations that indicate that sci­entists and engineers, in a paradigm shift, are making a fundamental break from the past. «Tailor-made" materials with controlled microstructures are beginning to emerge not only in polyolefins and other commodity thermoplastics, but also in polar thermoplastics, thermo­plastics elastomers, synthetic water soluble thermoplastics, high performance thermoplastics, high temperature thermoplastics, specialty thermoplastics for super-function membranes, con­ducting thermoplastics, polymeric nonlinear optical (NLO) materials systems, liquid crys-talline polymers, and advanced thermoplastics composites for structural applications. ·

This Handbook of Thermoplastics underscores these emerging developments and serves as an authoritative source for a worldwide audience in industry, academia, govern­ment and nongovernment organizations. It provides comprehensive, up-to-date coverage for each thermoplastic in terms of the following:

• History, development, and commercialization milestones • Polymer formation mechanisms and process technologies • Structural and phase characteristics as they affect use properties • Blends, alloys, copolymers, composites and their commercial relevance • Processing, performance properties, and applications • Any other issue that relates to current and prospective developments in science,

t~chnology, environmental impact, and commercial viability

v

PAGE 11 OF 47

vi Preface

These points were regarded as guidelines and every contributor was urged to choose a polymer-specific format that would make the handbook a timeless reference. A thorny element for each author, and indeed a most important issue that will continue to challenge the thermoplastics industry into the next century, relates to environmental waste. The industry has worked long and hard to develop products capable of withstanding extreme and/or aggressive conditions and having a long life. The rapid proliferation of thermoplastics in an impressive array of applications is evidence of the success of the thermoplastics industry, but this very success implies that many thermoplastics, discarded after they have fulfilled their purposes, will pose a formidable disposal challenge.

The Handbook of Thermoplastics is composed of 42 chapters prepared by 70 con­tributors from 18 countries. It contains more than 4000 bibliographic citations plus over

. 500 tables and figures. Each chapter includes full references at the end of each chapter. Each chapter has been edited, reviewed and revised where necessary, but the authors are responsible for the content. Although no attempt was made to rigorously group the chapters into subsections, there are some subtle groupings as well as grouping overlaps. This is inspired by the reality of the changing thermoplastics industry with its overlapping product families, flexible output, and thermoplastics applications. A pragmatic approach was taken, based on the conventional wisdom embodied in the broad classification of thermoplastics in terms of their applications loosely superimposed on their general spectrum of perfor­mance properties, namely, commodity, transitional, engineering, high performance, and high temperature. The final outcome, representing a cohesive treatment premised on this particular perspective, illustrates the phenomenal progress and the still evolving panoply of thermoplastics.

The first 12 chapters focus on polymeric materials that are essentially ethenoid in origin. Chapters 1 and 2 are devoted to polyolefins; Chapters 2, 3, and 4 treat stereoregular nonpolar and polar thermoplastics; and Chapters 4, 6, and 7 relate to styrenic thermo­plastics. Water-soluble polymers (Chapters 12 and 13) are discussed prior to the thermo­plastics based on cellulose (Chapter 14), the most abundant organic substances found in nature. Elastomeric materials are discussed in Chapters 15, 16, and 17. The polyester­based polymers are covered in Chapters 17-20, while polyarylates (Chapter 25), which are wholly aromatic polyesters, and the Hquid crystalline polymers (Chapter 41), which include a significant percentage of polyester-based materials, appear independently because of their uniqueness.

The compatibilized thermoplastic blends (Chapter 21) are intimately related to, and indeed form the basis for, some of the key methods used in the toughening of thermo­plastics (Chapter 22). The current and emerging engineering, high performance, and high temperature thermoplastics are contiguous to each other (Chapters 18-20, 23-33, and 36-41), interspersed with a few general but related chapters. To achieve some dovetailing, the chapters on conducting thermoplastics (Chapter 34) and conducting thermoplastics composites (Chapter 35) are placed after polyphenylene sulfide [PPS] (Chapter 32) and polyphenylene vinylene [PPV] (Chapter 33). This is because PPV, even without a doping agent, possesses a good measure of intrinsic conductivity, and PPS, upon doping with selected agents, is capable of significant electron conductivity. The advanced thermoplas­tics composites (Chapter 42) are discussed last to permit the prerequisite discussion of the relevant matrix materials on which the various composites are based.

It is hoped that this single-volume collective work will serve its intended purposes, contributing to the dialogue on questions that will continue to arise: What should be the priorities and targets for future development and future investments in the thermoplastics industry? What are the prospective developmental patterns? What will be the available

PAGE 12 OF 47

Preface vii

opportunities and the prevailing threats? What are the possible strategic approaches? What, in short, are the new sets of thermoplastics products that are likely to be produced and what process technologies are likely to be used to manufacture them in the 21st century and beyond?

The efforts of the contributors in preparing and revising their manuscripts for the handbook are deeply appreciated. During the course of preparing her manuscript, the author of Chapter 4, Vittoria Vittoria, lost her husband, Francesco de Candia, who made outstanding contributions to the study of syndiotactic polystyrene. I commend her forti­tude; her contribution is an essential memorial essay. Life, they say, is intimately entwined with death. I congratulate Emilia Di Pace on the birth of a child during the course of preparing her co-authored manuscript. I am delighted to thank M. Jamal El-Hibri for his support and for relaying information to some specific contributors. I acknowledge the support of the Research Institute, King Fahd University of Petroleum and Minerals, Dhah­ran, Saudi Arabia. As always, I am indebted to my wife and friend, Juliet Enakeme Olabisi, for a considerable amount of assistance, and to the youngest members of the family­Toyosi, Wande, and Simisola-who, though apparently unimpressed by the handbook project, diligently handled the attendant volume of fax messages.

Olagoke Olabisi

PAGE 13 OF 47

Contents

Preface

Contributors

1. Conventional Polyolefins Olagoke Olabisi

2. New Polyolefins Michael Arndt

3. Stereoregular Polar Thermoplastics Olagoke Olabisi and Michael Arndt

4. Syndiotactic Polystyrene Vittoria Vittoria

5. Unplasticized Polyvinyl Chloride (uPVC): Fracture and Fatigue Properties Ho-Sung Kim and Yiu-Wing Mai

6. Acrylonitrile-Butadiene-Styrene (ABS) Polymers Moh Ching Oliver Chang, Benny David, Trishna Ray-Chaudhuri, Liqing L. Sun, and Russell P. Wong

7. Styrene Copolymers Martin J. Guest

8. Polyacrylonitrile J ohannis C. Simitzis

v

xiii

1

39

57

81

107

135

161

177

ix

PAGE 14 OF 47

X

9. Polyacrylates Thomas P. Davis

10. Polyacrylamides David Hunkeler and Jose Hernandez Barajas

11. Vinyl Acetate Polymers C. Fonseca

12. Vinyl Alcohol Polymers Shuji Matsuzawa

13. Synthetic Water-Soluble Polymers Edgar Bortel

14. Cellulose Plastics David N. -S. Hon

15. Thermoplastic Elastomers Naba K. Dutta, Anil K. Bhowmick, and Namita Roy Choudhury

16. Thermoplastic Polyurethanes Kuo-Huang Hsieh, Der-Chau Liao, and Yuan-Chen Chern

17. Polyester-Based Thermoplastic Elastomers R. W. M. van Berkel, Rein J. M. Borggreve, C. L. van der Sluijs, and G. H. Werumeus Buning

18. Thermoplastic Polyesters Miguel Arroyo

19. Polyethylene Terephthalate Stoyko Fakirov

20. Polybutylene Terephthalate R. W. M. van Berkel, Edwin A. A. van Hartingsveldt, and C. L. van der Sluijs

21. Compatibilized Thermoplastic Blends Feng-Chih Chang

22. Toughening of Thermoplastics Ka11cheng Mai and Jiarui Xu

23. Polyacetal Wen-Yen Chiang and Chi-Yuan Huang

24. Polyethers Christo B. Tsvetanov

25. Polyarylates Miguel Arroyo

26. Polycarbonates Hoang T. Pham, Sarat Munjal, and Clive P. Bosnyak

27 . . · Polyamides Michail Evstatiev

Contents

203

227

253

269

291

331

349

381

397

417

449

465

491

523

557

575

599

609

641

PAGE 15 OF 47

Contents

28. Polyimides M oriyuki Sato

29. Polybenzimidazoles Tai-Shung Chung

30. Aromatic Polyhydrazides and Their Corresponding Polyoxadiazoles Emilia DiPace, Paola Laurienzo, Mario Malinconico, Ezio Martuscelli, and Maria Grazia Volpe

31. Polyphenylquinoxalines Maria Bruma

32. Polyphenylene Sulfide Gabriel 0. Shonaike

33. Polyphenylene Vinylene Louis M. Leung

34. Conducting Thermoplastics Sukumar Maiti

35. Conducting Thermoplastics Composites Ming Qui Zhang and Han Min Zeng

36. Poly(aryl ether sulfone)s M. Jamal El-Hibri, Jon Nazabal, Jose I. Eguiazabal, and Andone Arzak

37. Poly(aryl ether ketone)s Mukerrem Cakmak

38. Poly(aryl ether ketones-co-sulfones) Jacques Devaux, Veronique Carlier, and Yann Bourgeois

39. Poly(aryl ether ketone amide)s Mitsuru Ueda

40. Polytetrafluoroethylene Thierry A. Blanchet

41. Liquid Crystalline Polymers Francesco P. La Mantia and Pierluigi L. Magagnini

42. Advanced Thermoplastics Composites Gianfranco Carotenuto, M, Giordano, and Luigi Nicolais

Index

xi

665

701

733

771

799

817

837

873

893

931

951

975

981

1001.

1017

1035

PAGE 16 OF 47

26 Poly carbonates

Hoang T. Pham, Sarat Munjal, and Clive P. Bosnyak The Dow Chemical Compan~ Freeport, Texas

I. INTRODUCTION

There are two major classes of polycarbonates: aliphatic and aromatic [1]. Aliphatic poly­carbonates have not found any significant commercial use as thermoplastics. Most of the aliphatic polycarbonates are semicrystalline materials with low melting points, normally less than 120°C [2]. Aliphatic polycarbonates are used as plasticizers [3], as comonomers [4], and in copolymers such as polyurethanes [1] and blends [5] with bisphenol A poly­carbonates.

The most common aromatic polycarbonate is that derived from bisphenol A. Poly(bisphenol A carbonate), also known as poly carbonate (PC), is an amorphous polymer that possesses high heat resistance, is tough and transparent [6-8]. The use of PC spans from small consumer products such as tumblers to large-part applications in automotive and construction.

With its broad product applicability, the production of PC has grown tremendously since its first commercialization in 1958. The worldwide capacity of PC is 800,000 metric tons annually in 1991 [9] and current expansion has increased to over 1.1 million tons [10]. It is expected to continue to grow as more applications are being developed. Cur­rently,_ over 70% of the PC are manufactured in three major producers: General Electric under the trade name Lexan, Bayer (Bayer AG) under the trade name of Makrolon, and the Dow Chemical Company under the trade name CALIBRE. Other producers are GE Plastics Japan (GEPJ), Mitsubishi Gas Chemical Company Inc., Teijin Chemical, Idemitsu Petrochemical Company, Mitsubishi Samyangsa, Sumitomo-Dow, Enichem, and Policar­bonatos do Brazil. Currently, 44% of the PC produced in the United States, 26% in the Asia/Pacific region, and 30% in Europe. Other commercial uses of PC are in polymer blends. ·

609

PAGE 17 OF 47

610 Pham et al.

II. SYNTHESIS OF POL YCARBONATE

Poly(bisphenol A carbonate), or PC, is a condensation product of bisphenol A, a carbonate precursor such as phosgene or diphenyl carbonate, and a monophenol chain terminator such as phenol (11] or t-butyl phenol [11]. The structure of a linear PC is as shown:

CH3

Bisphenol A Poly carbonate (PC) .

The two currently used commercial methods for the manufacture of PC are described below.

A. I oterfacial Process

An interfacial process involves two-phase separated liquids systems whereby reaction oc­curs at. the interface of the two phases. This has been the most widely practiced method and is used for over 95% of the worldwide commercial production of bisphenol A PC. In this method an aqueous solution of bisphenol A and sodium hydroxide is reacted with phosgene to form oligomers, which then transfer from the aqueous phase to the organic phase, usually a chlorinated solvent such as methylene chloride.

CH3

NaO -@-t-@-- ONa + COCl2

CH3

CH2CI2 ---"11 .. ~ NaO aq.NaOH

0 II

OCOCl

The molecular weight of the oligomers continues to grow in the organic phase at the aqueous organic interface [12]. The rate of the chloroformate end group to the hydroxy end groups in the oligomers depends on pH [13], phosgene addition time, and amount of phosgene added [14]. This ratio can affect the molecular weight control of the final po­lymer [15]. An excess of chloroformate is usually desirable to obtain a high molecular weight PC. The oligomers are further polymerized to form the high molecular weight polymer by the addition of catalyst such as triethylamine.

0 II

NaO OCOCI aq.NaOH ----'JI)IIo~ PC Catalyst Terminator

A monophenolic terminator is added to control the molecular weight. The terminator type can slightly influence the impact properties of the polymer [16]. The formation of monocarbonate oligomer may be eliminated if the terminator is added after phosgenation [17]. The amount of oligomers can be further adjusted by controlling the molecular weight of the oligomers before the terminator is added [18]. The need to minimize phosgene usage is generally desirable to control the cost of manufacture. Control of pH [19], tem­perature [20], ionic strength in the aqueous phase [21 ], and the use of a phase transfer catalyst [22] are described in the literature to obtain good molecular weight control at low phosgene usage. For sterically hindered PC such as tetrabromobisphenol A, the use of dimethylaminopyridine catalyst is preferred [23]. .

PAGE 18 OF 47

Polycarbonates 611

Both batch reactor and continuous reactor processes are practiced industrially. This reaction is exothermic and requires removal of heat. The phosgenation reaction is fast and can be completed using static mixers in a tubular reactor [24]. Usually phosgene addition/ heat removal controls the phosgenation time in the batch reactors.

After polymerization is complete, the aqueous portion is normally removed using a centrifugal separator. If desired, the polymer is then washed with a dilute base to remove the excess monomers in the organic phase followed by contact with acid to neutralize the base and extract the catalyst. The acidified polymer is then washed with water to remove the salt.

Some of the methods to remove the solvent from the polymer are (1) steam flashing of methylene chloride [25], (2) anti -solvent precipitation [26], and (3) contacting with hot water with mechanical kneading [27]. The porosity and the size of the particles pro­duced depends on the method used. Sometimes, a finishing step, such as countercurrent stripping, is required to achieve very low levels of residual solvents. A drying step to remove the water is also needed when steam/hot water is used for evaporating the solvent.

B. Transesterification Process

The transesterification process, used successfully for polyethylene terephthalate production, was originally used to make PC in the laboratory. However, color formation at the high reaction temperature and lack of adequate equipment, even recently, to handle the high­viscosity polymer prevented commercialization of this technology. This process does not require the use of solvent, water, or phosgene and is claimed to have cost advantage. Recently, GEPJ started a commercial plant in Japan using the melt transesterification pro­cess [28]. Bayer has also announced its intentions to build a demonstration plant [29]. Many of the other PC producers are presently researching this technology as indicated by the patent literature.

In this process, bisphenol A is reacted with diphenyl carbonate at 180-300°C in the presence of a catalyst.

CH (Q)- ft -© 180-300·c -<Q) HO OH + 0 0-C-0 0 PC + HO 0

Catalyst 3 n

Slight excess of diphenyl carbonate is used to achieve high molecular weights. The con..: densation product is phenol and needs to be removed. High gas-liquid surface area at high viscosity for the phenol removal is achieved in a self-cleaning twin-screw paddle extruders [30]. High vacuum, less than 1 mm Hg, is required in the final states of poly­merization. The catalyst is neutralized after the reaction is complete [31]. Material of construction [32], catalyst type [33], water [34] and organic impurity in the monomers [35], and the temperature profile all require careful control to obtain low-color PC.

Recently, a solid. state process has been proposed as a low-temperature alternative to the melt transesterification process [36]. This is a low-catalyst process that allows the production of high molecular weight polymer. The prepolymer (approximately 5000-10,000 Mw) is made using a process similar to the melt transesterification process. Alter­nately, the prepolymer can be made using the interfacial methods [37]. The prepolymer is then crystallized using acetone [38]. The crystallization prevents particles from sticking to each other during further polymerizatiqn at 220-240°C under vacuum or nitrogen flow. An increasing temperature profile could be used to achieve high molecular weights [39].

PAGE 19 OF 47

612 Pham et al.

C. Synthesis of Branched Polycarbonates

Branching increases the melt tension of the polymer without increasing the melt viscosity at high shear rates [ 40]. Branched PCs can be synthesized using any of the previously described processes by addition of a small amount of polyfunctional branching agent monomer. Polyfunctional monomers used as branching agent can be triphenols [41,42], tetraphenols [ 43-45], polyfunctional hydric phenols [ 46], and hydroxycarboxylic acid­type branching agents [47]. Examples of branching agents commonly used are tris(hy­droxyphenyl)ethane [ 48] and trimellitic trichloride [ 49].

Ill. STRUCTURE OF POLYCARBONATES

A. Molecular Weights and Molecular Weight Distributions

Since most properties are dependent on PC molecular weight, special attention in its characterization is considered here. The molecular weights of PC can be characterized by several methods. A common method reported in the patent literature to characterize PC chain length is the dilute solution viscosity. This method measures the viscosity average molecular weight utilizing the Mark-Houwink-Sakurada relationship:

['fJ] = KM~ (1)

where K and a. are constants that depend on the solvent used and the test temperature. In most cases, methylene chloride is used and the test temperature is 25°C. In that case, the constant K is 1.19 X 10-4 and a. is 0.8 [50] for ['fJ] in dl/g. There are several reported values for K and a. for methylene chloride. Other common solvents used are chloroform [51-53], tetrahydrofuran [54], dioxane [55], ethylene chloride [52], tetrachloroethane [52], and butyl benzene ether [50].

Another common method for determining the molecular weight of PC is gel per­meation chromatography along with an ultraviolet (UV) detector (GPC-UV). The GPC results give a molecular weight distribution from which the number average, weighted average, and z-averaged molecular weights can be determined. The values of molecular weights determined by GPC-UV will be used throughout this chapter.

Other methods used in characterizing the molecular weights are low-angle laser light scattering (LALLS), osmotic pressure, diffusion, and sedimentation. In some cases, a com­bination of GPC or dilute solution with LALLS is used for determining the molecular weights and the distribution.

Depending on the method of synthesis, PC weight average molecular weights can be obtained in the range from 13,000 to about 200,000 g/mol [1, 7]. The most useful range of PC is Mw 24,000-80,000 g/mol. The lower molecular weight range can be extended down to about 17,000 g/mol and is' used for optical disk applications [56,57]. At the upper range, PCs with molecular weights greater than 38,000 g/mol have a high melt viscosity and are very difficult to melt-fabricate in a conventional manner. Applications of PC with molecular weights above 70,000 g/mol include cast sheet and films [58], and blends with lower molecular weight PCs for improved toughness [59].

B. Structure Characterization

The bisphenol A PC backbone structure has C=O' that exhibits infrared absorption bands at 1770 em-\ C-0 at 1220-1 and 1235 em-\ and phenol OH at 3595 em - 1 [1,2]. A

PAGE 20 OF 47

Polycarbonates

PC12.BMFR.BISPHENOL.A.POLYCARBONATE.PHAM

160 1 145 140 135 1 ' 125 120 115 110 105 100 95 90 85 80 75 70 65 60 I I I

......::::t"- ICl - ~ = ICl - l.l'X'\IC::I"-'<1' -C\1 -Figure 1 An infrared spectrum of a poly(bisphenol A carbonate).

0 ....

613

25 20

typical infrared spectra for PC is shown in Fig. 1. Under 13C NMR, PC (Fig. 2) shows a multiplet chemical shifts at 7.25 ppm that is assigned to the 1,4-substituted phenyl hydro­gen and a singlet chemical shift at 1.68 ppm that is assigned to the methyl hydrogen. Using a high-power dipolar decoupling, magic-angle spinning, and cross-polarizer 13C solid-state NMR, the spectral peaks were assigned as (1) 31 ppm-due to methyl carbon, (2) 43 ppm-due to quaternary carbons, (3) 121, 128-due to aromatic carbons directly bonded to hydrogen atom, and (4) 150 ppm-due to aromatic carbon on the 1-4 phen­ylene axis [60].

C. Relaxation Characterization

The structure of bisphenol A PC has also been probed using various relaxation character­ization techniques which include deuterated NMR [61-63], neutron scattering [64], di­electric relaxation [65], and dynamic mechanical spectroscopy (thermomechanical tech­niques) [66-68]. A typical dynamic mechanical spectroscopy temperature scan for a PC resin tested at 1 Hz and 5°C step temperature is shown in Fig. 3. Three main relaxation processes are shown in the thermomechanical scan. The a transition identifies the tem­perature where long-range molecular motion is dominant. The temperature at which this transition occurs is known as the glass transition temperature (T8). The second transition that occurs at a temperature of about 60°C is known as the (3 transition. This transition is dependent on the thermal history of the test sample. The third peak, known as the 'Y transition, occurs at about -100°C. The loW-temperature, high-impact strength of PC has been associated with this 'Y transition [ 64]. The assignment of these relaxation processes for each peak is summarized in Table 1. Included in Table 1 are the proposed relaxation mechanisms for the 'Y transitions as studied by various experimental techniques.

PAGE 21 OF 47

.015

.01

C1) u 1::: c .D 0 "" ~

I

.005

-i

3500

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3000

25

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2000

W

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. Num

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PAGE 22 OF 47

Polycarbonates

1011 ~-------------------------------------------------------------------,

1010

-N

~ 109 U) Q) c: >-~

C> 108 .....

0

C>

~ Storage Modulus 107 -a- Loss Modulus

1()6 0.0 0.2 0.4 0.6 0.8 1.0

Dimensionless Temperature, TIT 9

Figure 3 Reduced temperature sweep dynamic mechanical spectrum of poly(bis­phenol A carbonate) tested at soc per step and at 1 Hz.

IV. PROPERTIES OF POL YCARBONATES

A. Mechanical Properties

1.2

615

The tensile modulus, the ultimate tensile strength, the yield strength, the elongation at yield, and the elongation at break (ultimate strain) obtained from an engineering stress­strain are some of the key properties used in the selection of materials and engineering

Table 1 Relaxation Mechanisms Proposed for the Transitions of Polycarbonates

Transitions

Ol.

Mechanism

Long-range segmental motion Isotropic reorientation of CO group, uncorrelated backbone ro­

tation producing conformational changes Long-range cooperative motion of several monomer units NMR-backbone motion restricted, phenyl ring undergoes

large-angle jump between two sites ('IT :flips) Broad-band dielectric-coupling motions of phenyl rings and

carbonate group . Dynamic mechanical-cooperative motion of 7 repeating units Neutron scattering-cooperative motion of two phenylene

group (but not more than 1 monomer unit) which include the CO group

Model-cis-trans/trans-trans reorienting causing phenyl group to flip about its 1,4 axis while backbone motion is restricted

Ref.

65 61, 62

65

67, 68 64

63

PAGE 23 OF 47

616

ID ID Q)

70

60

50

!:l 30 til

20

l.O

0

(\ : . . ... ! . i .. i ,"'--_______ ............ . • '"'*"" . . . . .

0 0.2 0.4 0.6 0.8 Strain

1

Figure 4 An engineering stress-strain curve for a 29,000 g/mol poly(bisphenol A carbonate) resin tested according to ASTM D-638.

Pham et al.

design of parts. The engineering stress-strain curve for a PC resin tested according to ASTM D-638 type I is shown in Fig. 4.

The typical physical properties of PC with various molecular weights are tabulated in Table 2 [69]. As shown, the mechanical properties such as modulus are essentially insensitive to molecular weights in the range shown. This is true for PC of molecular weight at least 10 times that of the entanglement molecular weight Me, which is measured and quoted in the range of 1700-2500 g/mol [70-74]. Under similar testing conditions, the yield stress increases slightly with decreasing molecular weight and the ultimate elon­gation decreases with decreasing molecular weight. Usually, PC undergoes stable drawing in tension following yielding. During stable drawing, the natural draw ratio, X.m of PC is about 1.8 [75]. This natural draw ratio is found to be only slightly dependent on PC molecular weight in the range of 18,000-38,000 g/mol at room temperature. Ultimate extensibility in tension is dependent on the molecular weight and on specimen defects such as trapped dust particles or surface scratches.

B. Toughness

It is generally recognized that ''toughness'' of poly(bisphenol A carbonate) arises from yielding process that allows large-scale deformation within the time scale of the loading event. However, a change in failure mechanism of PC from ductile to brittle, i.e., from high to low toughness depending on molecular weight, temperature, thickness, stress state,

PAGE 24 OF 47

Polycarbonates 617

Table 2 Typical Properties of CALIBRE 300 Grades Polycarbonate Resins

CALIBRE 300 series general purpose polycarbonate resins

Property ASTM 300-4 300-6 300-10 300-15 300-22

Melt flow rate, g/10 min D-1238 4 6 10 15 22 Deflection temperature, oc D-648 132 129 128 126 125

(unannealed at 1.8 MPa) Specific heat, J/kg K C-351 1256 1256 1256 1256 1256 Thermal conductivity, J/m2 C-177 0.195 0.195 0.195 0.195 0.195

K Coefficient of thermal D-696 6.8 X 10-5 6.8 x lo-s 6.8 X 10-5 6.8 X 10-s 6.8 X 10-5

expansion, m/m oc Tensile yield strength, MPa D-638 62 62 62 62 62 Tensile ultimate strength, D-638 72 72 71 71 65

MPa Tensile elongation at yield, D-638 7 7 7 7 7

% Ultimate tensile elongation, D-638 150 150 150 150 150

% Tensile modulus, GPa D-638 2.4 2.4 2.4 2.3 2.3 Flexural strength, MPa D-790 96.5 96.5 96.5 96.5 96.5 Flexural modulus, GPa D-790 2.4 2.4 2.4 2.4 2.4 Compressive strength, MPa D-695 69 69 69 69 69 Shear yield strength, MPa D-732 41 41 41 41 41 Shear ultimate strength, D-732 62 62 62 62 62

MPa Notched Izod impact (25C, D-256 960 910 910 850 750

10 mils notch, 1/8 in. thick), J/m

Tensile impact strength (S- D-1822 _630 590 530 460 380 type), kJ/m2

Rockwell hardness, D D-785 118 118 118 118 118 Instrumental dart impact 94 90 87 87 72

(1/8 in. thick, 3.39 m/sec, 25°C) Total energy, J

Source: Ref. 69. (Courtesy of The Dow Chemical Company.)

and rate of deformation, is widely reported [76-79]. The challenge is to predict the ductile-brittle transition for specific applications. At present, the general practice is to design for strength and toughness without consideration of the aspects of time.

The notched Izod impact test for plastics was modified from metals testing and is thought to indicate expectations of material behavior in parts with notches or ribs in impact. The room temperature notched Izod impact for an injection molded bar is about 900 J/m2

• Notched Izod impact can be used to determine the temperature at which the failure mechanism changes from ductile to brittle. This temperature is commonly known as the ductile-brittle transition temperature (DBTT). The room temperature notched Izod impact and DBTT of PC is strongly dependent on the molecular weight of the PC. This is shown in Fig. 5, a plot of DBTT, determined from 10-mils-radius notched samples which are Izod impact-tested at 5 mph, as a function of molecular weight.

PAGE 25 OF 47

618

0.85

0.80

en t: I= 0.75 m Cl

0.70

0.65

0.60 '----------'--------'----------l 0.1 0.2 0.3 0.4

Figure 5 Dimensionless plot of reduced ductile-brittle transition temperature (DB'IT/Tg) as a function of molecular weights (Me!Mn)·

Pham et al.

Fracture toughness measurements (surface energy dissipated to advance a crack) under controlled deformation rates with various crack lengths is thought to offer a more quantitative measure of toughness [76]. The fracture toughness of PC was investigated [80] using the double-torsion method. Figure 6 (from Ref. 80) shows the fracture energy as a function of PC molecular weight. At molecular weight less than 22,000 g/mol, the fracture energy is low and weakly dependent on molecular weight. Above a molecular weight of 22,000 g/mol, the fracture energy increases dramatically. This experiment, how­ever, is only valid for brittle failure. For ductile failure, the fracture energy cannot be determined from this test method because of the additional large energy dissipated by a zone of yielded material associated with and ahead of the crack tip. In these cases, the "crack layer model" appears most suitable to describe the crack growth in PC [75,81,82].

Another aspect in designing engineering parts is the time-dependent failure mecha­nisms of the materials. The time-dependent failure can be assessed by time-dependent creep experiments. In such experiments, the creep responses of PC were assessed [83-85]. At loadings greater than the draw stress of PC (about 45 MPa) but lower than the yield stress (about 60 MPa), PC undergoes yielding. However, when subjected to loadings lower than the draw stress, PC forms microcracks with time [85].

Lifetime prediction is one key element in the determination of the durability and performance of the engineered part. In most cases, lifetime predictions were performed using fatigue crack initiation and growth studies [86]. The resistance to crack propagation under fatigue for PC is, like impact behavior, highly dependent on molecular weight,

PAGE 26 OF 47

Polycarbonates

3000

2500

..r .€ ::2. ~ 2000 >; ~ <1> c UJ

~ 1500 ::I 0 ~ u..

1000

500

0 L-----~----~~----~----~~----~----~ 16000 18000 20000 22000 24000 26000 28000

Molecular Weight (g/mole)

Figure 6 Fracture energy of poly(bisphenol A carbonate resin) as a function of weight average molecular weights. (From Ref. 80.) Reprinted with permission. Cour­tesy of the Society of Plastics Engineers.

619

specimen geometry, physical aging, etc. This is due to the changes in the contribution. of the shear lip or band and plane strain craze formation [87]. A fatigue fracture diagram for notched knit line samples for PC at various temperature-stress levels ~howed similar failure mechanisms [88]. The PC failure mechanisms under fatigue at various loading were proposed as a fatigue-fracture initiation mechanism map as illustrated in Fig. 7 [89,90]. Figure 7 (from Refs. 89 and 90) is a fatigue fracture map showing the fracture mechanisms for PC samples with molecular weight of 29,000 g/mol as a function of sample thickness and the applied loading normalized with the yield stress. The failure mechanisms were described to possess brittle failure at low stresses, ductile failure at high stresses, and mixed-mode failure at intermediate stresses.

C. Optical Property

PC has a nominal refractive index of 1.538 compared to glass with 1.52. The refractive index varies with the wavelength of the incoming light beam. At a wavelength of greater than 600 nm, the refractive index is in the range of 1.58 and increases to 1.61 at wave­length of 400 nm [91]. This optical property coupled with its toughness makes it a unique engineering thermoplastics for use in precision optic applications. Furthermore, this prop­erty has enabled researchers to study the effect of processing on the molecular orientation

PAGE 27 OF 47

620

Figure 7 Fatigue fracture mechanism map for polycarbonate with weight average molecular weight of 29,000 g/mol tested at room temperature. [Portion of the graph is reproduced from T.-J. Chen, A. Chudnovsky, and C. P. Bosnyak, J. Appl. Polym. Sci. 49: 1918 (1993) (copyright John Wiley and Sons) and J. Mat. Sci. 29: 5904 (1994) (copyright Chapman and Hall). Reprinted with permission. Courtesy of John Wiley and Sons and Chapman and Hall.]

Pham et al.

and residual stresses resulting from fabrication via the birefringence using optical methods [92-94]. PC has a light transmission of above 87%. In critical applications, the light transmission of PC is normally greater than 90%.

D. Thermal Properties

Another attribute of PC is its high heat tolerance. Polycarbonates with molecular weights in the range 18,000-38,000 g/mol have glass transition temperatures, Tg, in the range 140-155°C. Due to the high Tg, PC has a high heat distortion temperature under load (HDT or DTUL). The temperature at which the sample deflects 0.25 mm at 1.84 MPa load (deflection temperature under load, DTUL) for PC with molecular weights between 26,000 and 38,000 g/mol ranges from 132°C to 138°C. The Vicat softening temperature, which is the temperature at which a specified flat-head needle penetrates 1 mm into the

PAGE 28 OF 47

Polycarbonates 621

specimen at a given force, for PC with molecular weight in the range 26,000-38,000 g/mol is 154-158°C.

E. Stability

PC is normally fabricated at high melt temperatures (300°C and above) where yellowing and molecular weight degradation ·can occur in the presence of impurities like water, oxygen, iron [95], and residual base [2]. It is recommended that PC be dried below 200-500 ppm water [96] to prevent loss in toughness. The presence of base can cause yellowing, branching, or crosslinking. Under controlled conditions, the residual base can be used for obtaining narrow dispersity polymer by the transesterification mechanism [97]. Thermal-oxidative stabilizers for PCs are usually hindered phenols [98], phosphonites [99], phosphines or phosphates [100] based compounds and/or combinations of phenols and phosphorus compounds [101,102].

Under prolonged exposure to UV light, PC tends to yellow and degrade due to photooxidation reaction. PC undergoes a photo-Fries rearrangement from 1T state to 1T*1

state [103-106] that usually does not affect the layers beyond 250 J.Lm from the surface. Surface crack formation may cause PC to be brittle. For outdoor applications, PC is nor­mally protected by adding a UV stabilizer which protects the PC by selective absorption of the harmful UV radiation. Common UV stabilizers employed are benzotriazoles [107,108] and benzophenones [109]. Methods of UV stabilizer addition to the surface of an article prepared from PC are a lacquer coating layer, solution embedment on the PC skin [110-114], or coextrusion [109,115]. In other cases, incorporation in the resins are also utilized.

In high-humidity and high-temperature applications, the hydrolytic stability of PC becomes important. PC has an equilibrium moisture content of 0.34% at 25°C and 0.48% at 100°C and 100% relative humidity. Impurities in PCs may, however, react with water and cause degradation of the mechanical properties. Some additives normally added to PC may also accelerate the hydrolytic degradation of PC at temperatures above 60°C. This process will eventually decrease both notched Izod impactand molecular weight [116-119].

F. Rheology

Polycarbonates are commonly specified in terms of melt flow rate (MFR). The melt flow rate is determined using a plastomer as described in ASTM D-1238 (DIN 53735). The test conditions are a 1.2-kg load at 300°C. The MFR, as measured for linear PC, can be correlated to the molecular weights via the zero shear viscosity [120,121].

The melt flow behavior of PC is quite different from other polymers. It possesses a wide range of shear rates where the shear viscosity is Newtonian. At high shear rates, the shear viscosity is pseudoplastic. The critical shear rate at which the viscosity changes from Newtonian to pseudoplastic behavior decreases with increasing Mw. Figure 8 shows a typical characteristic flow curve of PC resin. In this figure, the material is a 3-MFR PC resin. tested at 270, 285, and 300°C. The shear viscosity as a function of shear rate and temperature can be described using the modified Cross model with an Arrhenius or the WLF temperature dependence expressions. For the WLF form, the modified Cross model can be expressed as [121]:

1.5pTA. '"11(')', T) = 1 + (A.-y)o.s (2)

PAGE 29 OF 47

622

en I co

e:. (::"

~ (/) 0 0 (/)

5 Cii (J)

..c: en

104 .-------------------------------------------------------------,

103

1~ L_ ____ L-~--L-~~~L-----~~--~~~~L-----L-~--~~~~

101 1~ 1~

Shear Rate at the Wall (sec"1)

104

Figure 8 Characteristics flow curves of a 37,000 g/mol poly(bisphenol A carbon­ate) resin at various temperatures.

Pham et al.

where n = 0.8, p is the melt density in kg/m3, Tis the absolute temperature in Kelvin,

and X. is the characteristic relaxation time in seconds. The effect of molecular weight on the zero shear viscosity is found to obey the 3.4

power law [121] and some reported a 4.2 power [122]. For the 3.4 power law case, the effect of molecular weight on the shear viscosity can be expressed as [121]:

'rJo = 1.5pTX. (3)

where

X. = 1 4 X 10-21 M 3A exp(

1 )

• w f3(T- T=) (4)

and

f3 = 8 X 10-4 K

Another aspect of rheology for processing is the viscoelastic nature of the polymer melts. The elastic recovery strain for PC ranges from 1.1 to 2 depending on the molecular weight [123]. This low elastic behavior is also seen in the low entrance and exit pressure drop across a sudden contraction such as in a capillary rheometer as determined by Bag­ley's correction [124].

The effect of branching on the shear viscosity of PC was found to increase the zero shear viscosity at the same GPC molecular weight. At high shear rates, the shear viscosity decreases below that of the linear PC at the same GPC molecular weight. As an example, CALIBRE* 600-3 branched PC has a MFR of 3 as measured by ASTM. D-1238 at the low--shear region and processes like a 5-MFR linear PC at the high-shear-rate region. This effect has been found desirable for extrusion and blow-molding applications.

PAGE 30 OF 47

Polycarbonates

V. MODIFICATIONS OF POLYCARBONATES

A. Impact Modifications

623

Although PCs are generally tough, under prolonged exposure to heat and/or stresses, the impact toughness decreases with time. This is related to the volume relaxation or changes in free volume [125-127]. The impact toughness of PC after aging and the low molecular weight PC can be managed by addition of an elastomeric phase in the PC, known com­monly as impact modification. Examples of elastomers employed are styrene-butadiene­styrene triblock copolymer (SBS) [128], styrene acrylonitrile grafted onto ethylene-pro­pylene-diene rubber (SAN-g-EPDM) [129], and methacrylate-butadiene-styrene rubber (MBS) [130]. A typical commercial grade of impact-modified PC is CALIBRE 400-18 polycarbonate resin [131] (physical properties tabulated in Table 3), which can be used for a wide range of application requiring durability, easy processing, and toughness. For the lower Mw PC, the DBTT can be reduced by impact modification. As an example, using 10% SAN-g-EPDP, the DBTT of the impact-modified PC can be reduced to below -40°C [129] compared to about -10°C unmodified.

B. Fillers

Fillers are selected based on cost and desired performance. Addition of fillers to PC are done for some applications that require high modulus, stiffness, abrasion resistance, anti­static behavior, and low coefficient of thermal expansion (CLTE). Important parameters for toughness are the average particle size and its distribution. The higher the aspect ratio, the higher the modulus for a given volume fraction of filler. Typical fillers added to PC are surface-modified short glass fibers [132-134], wollastonite, carbon fiber [134], and titanium oxide (Ti02 ) [135]. These fillers have a higher surface area factor due to their shape. In Table 3, the physical properties of a typical glass fiber-filled PC, i.e., CALIBRE 5200, are summarized [131]. Additionally, glass fibers have an advantage in that the notched impact toughness can be maintained about 6 kJ/m2 compared to other· fillers. Furthermore, the impact toughness is little affected by temperature even down to - 30°C. Metal fillers such as aluminum [136] or metal alloys are added to PC for thermal and electrical conductance improvements. Molybdenum sulfide, graphite, and polytetra­fluoroethylene (PTFE) are also sometimes added to PC for abrasion and low wear resistance.

C. Flammability

Polycarbonate has an oxygen index of about 26-28% as tested according to ASTM D-2863. It is rated as V-2 at 1.6 mm according to UL94. For applications that require higher ignition resistance, additives such as bromine compounds [137,138], sulfur compounds [139-141], phosphorus compounds [142-144], silicone compounds [145,146], antimony compounds [147,148], fluorine-containing polymers [149,150], and combinations of these compounds are added.

The ignition resistance mechanism of PC has been proposed [151,152] as follows: (1) thermal decomposition of PC, i.e., pyrolysis, then (2) formation of branched and crosslinked species at the flame that stabilize the flow of new materials to the flame for sustaining the flame, and (3) char formation. (4) If PTFE is pre­sent, it will enhance the stabilization of the material renewal to the flame and char formation.

PAGE 31 OF 47

624 Pham et al.

Table 3 Typical Properties of Modified CALIBRE Polycarbonate Resins

Glass-reinforced Impact-modified Ignition-resistant PC CALIBRE PC CALIBRE PC CALIBRE

P~operty ASTM 5200 400-18 700-6

Melt flow rate, g/10 min D-1238 3 18 6 Deflection temperature, oc

(unannealed at 1.8 MPa) D-648 138 121 129 Mold shrinkage, mm/mm D-955 0.006-0.008 0.005-0.007 Specific gravity D-792 1.326 1.185 1.2 Coefficient of thermal D-696 3.8 x lo-s 6.8 x lo-s

expansion, m/m °C Tensile yield strength, MPa D-638 59 58 61 Tensile ultimate strength, MPa D-638 48 66 Tensile elongation at yield, % D-638 4 7 Ultimate tensile elongation, % D-638 8 110 120 Tensile modulus, GPa D-638 3.1 2.2 Flexural strength, MPa D-790 94 90 100 Flexural modulus, GPa D-790 3.2 2.3 2.4 Notched Izod impact (25°C, D-256 107 641 908

10 mils notch, 1/8 in. thick), J/m

Tensile impact strength (S- D1822 589 type), kJ/m2

Rockwell hardness D-785 Rl23 Instrumental dart impact (1/8 51 87

in. thick, 3.39 m/sec, 25°C) Ultimate energy, J

Source: Data from Ref. 131. Reprinted courtesy of the Dow Chemical Company.

VI. PROCESSING OF POLYCARBONATES

Polycarbonates can be processed using conventional processes such as extrusion, profile extrusion, blow molding, injection molding, gas-assisted injection molding, thermoform­ing, and solution casting. PCs with molecular weights in the range of less than 35,000 g/ mol [153] are commonly used in injection-molding applications. For blow-molding ap­plications, due to the need of melt strength, a PC with a molecular weight of more than 32,000 g/mol is normally used. PC needs to be dried prior to processing to prevent deg­radation and foaming. Normally PC is dried using a convective dryer or oven at. about 120°C for at least 4 hr. The drying step can sometimes be bypassed if the PC is processed using a vented extruder.

Extrusion of PC is normally done using a screw with compression ratio of 2.0-2.3 with a nominal screw-length-to-diameter ratio of at least 24:1. The bulk density of PC pellets is in the range of 0.65-0.75 g/cm3

• The coefficient of dynamic friction of PC as measured using a screw simulator [154] is 0.6 at temperatures in the range 25-80°C, drum velocity of 0. 71 m/sec, and loading of 6.9 MPa. Since the coefficient of dynamic friction is higher than normal (normal in the range of 0.45-0.5), PC tends to feed faster and, coupled with its high viscosity, can generate high pressures if the screw design is not optimized. The melting mechanism of PC in a single-screw extruder is in accordance with the Tadmor and Klein model at the initial stage and differs from this model at the later

PAGE 32 OF 47

Polycarbonates 625

Table 4 Recommended Injection Molding Conditions for Various Polycarbonates and Blends

PULSE PC/ABS Property Unmodified PC Glass-filled PC Blend

Set temperature: Hopper, °C 70-90 70-90 70-90 Rear Zone, oc 275-290 300-320 230-270 Middle Zone, oc 280-300 310-340 250-280 Front Zone, oc 280-320 310-340 250-280 Nozzle, oc 280-320 310-340 250-280 Mold, oc :::;96 :::;130 :::;96

Melt temperature, oc <320 <340 <290 Clamping tonnage, MPa 41-69 69-96 41-69 Injection pressure:

1st stage, MPa <200 <200 2nd stage, MPa 100-120 100-120 70-100 Hold pressure, MPa <5 <5 <5

Shot capacity, % 30-85 Screw speed (velocity 0.5 0.35 0.5

at barrel surface), m/sec

Drying >4 hr@ 120°C >4 hr@ 120°C 3-4 hr@ 93°C

stage of melting [155]. This is very relevant, especially in profile sheet extrusion where extruder stability is required. The normal barrel set temperature for processing PC by extruder or injection molding ranges from 250°C to 300°C.

For injection molding, typical molding conditions for PC are tabulated in Table 4. In injection molding of intricate parts, thermally stable mold-releasing agents such as an ester of a trihidric alcohol and a C 10-C20 saturated carboxylic acid [156], monohydric neopentyl alcohol, i.e., pentaerythritol stearates [157], and fatty acid ester [158,159] are commonly added to PC. Due to the high melt temperature during fabrication, the purity of the mold-releasing agents is also very important. Traces of base may cause molecular weight degradation and therefore the degradation of properties of the injection-molded parts.

After processing PC, purging the injection-molding machine with high-density po­lyethylene is highly recommended. Upon solidification, PC can form a strong bond to the metal surface. This bond is strong enough to be able to detach the plated metal surface from the remaining core.

VII. APPLICATIONS

Polycarbonate with its combined properties of transparency, toughness, and high heat re­sistance has numerous applications ranging from small parts such as fuses to large sheets used in construction. Here are some important applications that capitalize on key prop­erties.

A. Optics

PC is normally used as the substrate in optical information media such as digital audio compact disk (CD) and compact disk read-only memory (CD-ROM) as shown in Fig. 9.

PAGE 33 OF 47

626 Pham et al.

Figure 9 Typical digitl;ll audio compact disk made from poly(bisphenol A car­bonate).

This application demands PC to be highly pure [160] with light scattering of less than 0.3 cd/(m2-lx) [161], transparency requirements of greater than 87% spectral light transmission for a 4-mm-thick sheet [161], colorless with requirements of a yellow index less than 4.5 [161], easy to process, and low birefringence due to molded-in orientation. Information stored in this type of media are in the form of pits as shown in Fig. 10. These pits are transcribed onto the PC substrate using a compression-assisted injection molding process. The disk is then aluminum-coated to reflect the incoming laser light. With the groWth in CD-ROM, laser disks for movies, and the recently developed read-and-write CD-ROM, the use of PC in this application will grow accordingly. The technical aspect of this application will also be very challenging as the specification requirements will be even more strict.

Other key optical applications of PC are in optical lenses [162], camera components [163], goggles and safety glasses. They are commonly used for their low weight and impact toughness compared to glass. However, PC itself is poor in scratch resistance. In this application, a scratch-resistant coating such as acrylate or silicate is commonly used.

B. Construction and Housing

Another usage of PC is in the sheet applications. CALIBRE 600 and 302 polycarbonate resin grades are specially formulated for these types of application. PC sheets are used in construction applications such as windows [164], laminated_ walls, infrared reflective in­sulation [165], and skylight roofing. Other uses of PC sheet can be found in household applications such as table and desk covers. In applications exposed to sunlight, UV-resis­tant coatings or special UV additives are added because PC tends to yellow and degrade (see "Stability"). Scratch resistance coatings are also required in most of these applica­tions. Furthermore, by changing the light scattering characteristics, opalescent PC can have applications such as light-diffusing roof covers and lighting components [166].

PAGE 34 OF 47

Polycarbonates

Figure 1 0 Typical micrograph of a close-up to a digital audio compact disk seen under an optical microscope at 6000 X magnification.

C. Business Equipment

627

PC is used extensively in business equipment, telecommunication devices, and electronics housings where high toughness is a requirement. Furthermore, special grades of PC such as CALIBRE 800 polycarbonate resins which have an ignition-resistant additive package and impact modifiers are specially formulated for these applications.

D. Automotive

Many automotive applications are often very demanding and well matched to the prop­erties of PC. Examples of such applications are speedometer needles [167], windscreens [168], instrument panels, head lamp covers and housings [168], and tool boxes. In most cases, the automotive applications are subjected to sunlight exposure and fire hazards. In such applications, ignition-resistant additives are used in combination with UV additives and impact modifiers. Other properties sometimes needed in these applications are paint­ability and adhesion to other materials such as polyurethanes. CALIBRE 401 polycarbon­ate ·resins ·are prime examples of resins that are used in these types of applications. For head lamp covers, the combination of high toughness, transparency, and heat resistance is the key property that makes PC the material of choice. In this application, a scratch­resistant coating that typically includes a silicone layer with UV stabilizers is normally

PAGE 35 OF 47

628 Pham et al.

used to protect the PC. At regions close to the light bulb, temperatures as high as 120-1400C can be reached.

E. Medical Devices

PCs are also used in dental applications [169], blood collector containers [170], disposable syringes, medical tubing, kidney dialysis tubings, and pacemaker components. In most applications, the PC must withstand a high temperature of 134 oc in an autoclave process for sterilization. Furthermore, -y-radiation resistance is sometimes required. Polyols [171], linolenic compounds [172], sorbate compounds [173], benzyl ether-type compounds [174], and disulfide comonomers [175] are added to PC for -y-radiation resistance.

F. Appliances and Consumer Products

In the consumer products category, PCs are used in applications such as dinnerware, drinking cups, and toys. These products can be either transparent or colored. These ap­plications require Food and Drug Administration approval. A key application in this cat­egory is blow molding, which requires high molecular weights and/or branched PCs with high melt strength.

In appliances and other household articles, applications where PCs are used include eyelets for shower curtains [176], crisper trays in refrigerators, and appliance housings that require ignition resistance, heat resistance, and impact resistance.

VIII. BLENDS AND COPOLYMERS

Two major trends in modifying PCs are blends and copolymers. Blending is a method in which a set of desired properties can be obtained from two polymers. There are two classes of polymer blends, namely, miscible and immiscible blends. Commercial immiscible blends, such as PC and acrylonitrile-butadiene-styrene copolymer (PC/ABS), or PC and polyesters such as polyethylene terephthalate (PC/PET), are used in various applications. Typical properties of PC/ABS and PC/PET blends [131] are summarized in Table 5. Some blends of PC with other polymers are summarized in Table 6.

Blends of PC with ABS, such as PULSE* brand PC/ABS, are used in automotive applications such as quarter panels and wheel covers. Other applications of PC/ABS blends are found in electronics and business equipment. PC and ABS adhere together well and give a balance of easy processibility, high heat resistance, and good low-temperature im­pact toughness. The compatibility of PC and ABS depends on the acrylonitrile content in the ABS [177]. The optimized composition for toughness as measured by ductile-brittle transition temperature was found to be in the range 60-70% PC [178]. Using X-ray scattering, the fracture surface of a PC/ ABS sample under tensile deformation showed shear yielding in the PC phase and rubber cavitation in the rubber phase [179]. The viscosity of PC/ ABS blends as a function of composition showed lower values than the linear relationship between the values of the pure components. The relationship best fitting the viscosity-composition of PC/ABS can be described by the Lecyar Model [180].

Immiscible blends of PC with polyesters, such as SABRE* brand PC/PET, are used in places where solvents resistance is required. The addition of PET, which is a semi­crystalline material, into PC improves the solvent resistance and weathering and enables

*Trademark of The Dow Chemical Company.

PAGE 36 OF 47

Polycarbonates 629

Table 5 Typical Properties of Polycarbonate Blends Resins

PC/ ABS blend Filled PC/ABS PC/PET blend Property ASTM PULSE 830 PULSE B250 SABRE 1664

Melt flow rate, g/10 min D-1238 3 2 8 (265°C/2.16 kg) (230°C/3.8 kg)

Deflection temperature, D-648 126 129 °C (unannealed at 1.8 MPa)

Mold shrinkage, mm/mm D-955 0.007 0.0065 0.006-0.009 Specific gravity D-792 1.13 1.2 1.2 Coefficient of thermal D-696 74. X 10-5 6.3 X 10-5 7.6 X 10-5

expansion, m/m °C Tensile yield strength, D-638 53 55 52

MPa Tensile ultimate strength, D-638 45 47 53

MPa Tensile elongation at D-638 4

yield, % Ultimate tensile elonga- D-638 125 90 130

tion, % Tensile modulus, GPa D-638 2.1 2.9 1.8 Flexural strength, MPa D-790 83 93 81 Flexural modulus, GPa D-790 2.3 2.9 2.1 Notched Izod impact D-256 641 320 747

(25C, 10 mils notch, 1/8 in. thick), J/m

Rockwell hardness D-785 R115 Instrumental dart impact 57 51 48

(1/8 in. thick, 3.39 m/ sec, 25°C) Ultimate energy, J

Source: Data from Ref. 131. Courtesy of The Dow Chemical Company.

the PC/PET blends be used in applications that have high solvent contact such as in lawn mower decks and automotive rear quarter panels. PC and PET are partially compatible due to the transesterification reaction between the two components [181-184]. The tran­sesterification reaction that occurs in PC/PET is similar to the reaction that occurs in PC/ PBT [185,186]. At concentrations of PET greater than 70% and less than 5%, the blends are transparent with one Tg [187].

For easier melt processing, high modulus, and toughness, blends of PC and liquid crystal polymers have been reported [188,189]. To date, these types of blends have not been commercially successful due to the additional cost factor and the anisotropic behavior of the blends after being fabricated.

The other class of PC blends is miscible blends. Only a few blends of this type are used commercially. Examples of the class of miscible blends with PC are with poly­caprolactone [190-192] and low concentrations of aliphatic polyesters [193,194]. Addi­tion of polycaprolactone decreases the low-temperature toughness and Tg due to plastici­zation. Miscible blends of low molecular weight and ultrahigh molecular weight PC produced from a solid state polymerization process have also been reported [195]. These

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630 Pham et al.

Table 6 Some Typical Polycarbonate Blend Systems

Polymer A Polymer B Property Ref.

PC ABS Compatible: increase compatible at 25- 217,218 28% AN content/due to SAN oligomer

PC PET Compatible-transesteri:fication 181-187 PC PBT Miscible at low concentration of PBT 194

Compatible-transesteri:fication PC Polycaprolactone Completely miscible 190-192 PC SAN Miscible (23-70% ·AN) 177

Compatible PC Polymethyl methacrylate Compatible-transesteri:fication 219 PC Polyarylates Compatible-transesteri:fication 220 PC Ethylene terephthalate Miscible 221

caprolactine copolyester

PC Polystyrene Compatible ( ~ 15%) 222 PC Polypropylene Compatible (~5%) 222

blends are claimed to have better melt strength and toughness, compared with the ho­mopolymers at the same molecular weight. Also, blends of linear and branched PC have been reported to have an enhanced crack resistance aside from being readily processable [196].

Another method of modifying PC for various applications is copolymerization and the variety of comonomer that can be copolymerized with bisphenol A can be found elsewhere [1,2,7,197]. One notable example is the copolymer of bisphenol A and bis(9,9 hydroxyphenylfluorene) (BHPF) [198,199], used in ultrahigh heat applica­tions. Depending on the content of BHPF, the Tg can range from 150°C to 280°C. At certain concentrations of BHPF and molecular weight, these copolymers are amorphous and ductile. Other notable high-heat PC copolymers with bisphenol A include tetrabro­mobisphenol (TBBA PC) [200-202], trimethylcyclohexyl bisphenol (TMPC) [203], and hydroxyphenylcycloalkane (HPCA) [204]. TBBA PC has Tg ranging from 150 to 213° while TMPC has Tg ranging from 150 to 250°C and HPCA has Tg ranging from 180 to 230°C. These copolymers are typically used in applications requiring high heat and transparency. An example is the use of HPCA in the liquid crystal display devices [205].

New copolymers of bisphenol A with flexible chain monomers, i.e., aliphatic po­lyesters, are being developed for thin wall applications requiring greater melt flow than conventional PC can offer, i.e., greater than 22 g/10 min. For easier processing, lower molecular weight PC may be used, but a common problem encountered when using too low a molecular weight PC is cracking under no-external-load conditions [206]. These brittle cracks are the consequence of residual orientation and thermal stresses as a result of fabrication.

Copolymers of PC that address the easy flow applications include the PC having end-group modification with branched alkylphenyl [207], a copolymer with aliphatic po­lyester [208,209] that give better notched Izod impact at the same melt flow rate, and a copolymer with liquid crystal component [210,211] that provides easy access with im­proved mechanical properties.

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Polycarbonates 631

Another class of modified copolymers uses reactive end groups to form branching and/or crosslinking. Applications of these type of copolymers include scratch-resistant coatings and blow-molding applications. An example of these reactive end groups is the benzocyclobutene (BCB) end group [212-214]. At low concentration of BCB, the copo­lymer can be processed using conventional methods and it exhibits excellent melt strength [215]. At high concentrations, the copolymer forms a three-dimensional network that gives the hardness expected from a scratch-resistant PC coating [216].

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