Table Of ContentMaterials Science Series
C.B. Bucknall
Toughened
Plastics
TOUGHENED PLASTICS
MATERIALS SCIENCE SERIES
Advisory Editors
L. HOLLIDAY,
Brune/ University,
Uxbridge, Middlesex, Great Britain
A. KELLY, F.R.S.,
Vice-Chancellor, University of Surrey,
Guildford, Surrey, Great Britain
TOUGHENED
PLASTICS
C. B. BUCKNALL
Department of Materials, Cranfield Institute of Technology,
Cranfield, Bedford, England
Springer Science+Business Media, B.V.
ISBN 978-94-017-5351-7 ISBN 978-94-017-5349-4 (eBook)
DOI 10.1007/978-94-017-5349-4
WITH 163 ILLUSTRATIONS
© Springer Science+ Business Media Dordrecht 1977
Originally published Applied Science Publishers LTD in 1977.
Softcover reprint of the hardcover 1st edition 1977
All rights reserved. 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, or otherwise, without the prior
written permission of the publishers, Springer Science+ Business Media, B.V
PREFACE
Rubber-toughened plastics constitute a commercially important class of
polymers, which are characterised by a combination of fracture resistance
and stiffness. The best known members of the class are toughened
polystyrene, or HIPS, and ABS, but there are also toughened grades of
polypropylene, PVC, epoxy resin, and a number of other polymers. Each of
these materials is a composite polymer, consisting of a rigid matrix and a
disperse rubber phase. This book describes their manufacture, analysis,
mechanical properties and processing characteristics. The aim is to show
how structure can be controlled during manufacture, and how the
properties of the product are consequently affected.
The book is divided into three main sections. The first four chapters,
which are concerned broadly with the chemistry of toughening, cover phase
separation and compatibility, grafting, microscopy, analytical techniques
and methods of polymerisation. This section is of interest not only to
physical chemists engaged in research and development, but also to all who
are involved in the characterisation and quality control of rubber
toughened plastics. The second section, comprising six chapters, deals with
mechanical properties, including viscoelastic properties, creep, yield,
fatigue, fracture and impact strength. The effects of structure upon
properties and the role of crazing and shear deformation are discussed in
some detail. This section is of interest to aJI concerned in the manufacture
and applications of rubber-toughened plastics. The third section consists of
two chapters on the manufacture of finished components, covering melt
rheology, thermoforming, extrusion, injection moulding and electroplating.
The emphasis throughout is on the effects of adding rubber on the
manufacturing technology and product properties. Topics, such as solvent
crazing resistance, which are not considered to be affected significantly by
the addition of rubber, have been excluded or treated only briefly.
The field of rubber toughening provides many good examples of the
principles of materials science and technology applied to practical ends. For
v
VI PREFACE
this reason, the subject is of interest not only to specialists involved in the
industry, but also to advanced students of materials or polymer science. The
treatment followed in this book is designed to introduce the reader to a class
of materials which must surely rank amongst the principal inventions of the
plastics industry.
I should like to express my thanks to Dr M. J. Folkes, Dr R. P. Kambour,
Dr H. Keskkula, Dr T. D. Lewis, Dr A. E. Platt and Professor J. G.
Williams, each of whom read a portion of the manuscript and offered
valuable comments. I am also grateful to Mrs V. Collier and Mrs S.
Skevington for preparing the line diagrams, to Mr I. C. Drinkwater for
assistance in preparing the photographs, and to the authors and publishers
who granted permission for the use of previously published material.
Individual acknowledgements are made in the figure captions.
Department of Materials
Cranfield Institute of Technology
Cranfield C. B. BUCKNALL
CONTENTS
Preface v
Glossary Xlll
Chapter 1
THE GROWTH OF A TECHNOLOGY
1.1 The Balance of Properties
1.2 The Invention of Toughened Polystyrene 2
1.3 New Materials and Expanding Markets 3
References 8
Chapter 2
COMPATIBILITY AND COPOLYMERISATION
2.1 Introduction . 9
2.2 Compatibility 9
2.2.1 Flory-Huggins theory 10
2.2.2 Solubility parameter II
2.2.3 Partial miscibility. 15
2.2.4 Equation of state thermodynamics 18
2.2.5 Tests for compatibility . 19
2.2.6 Effects of compatibility upon properties 20
2.3 Copolymerisation . 21
2.3.1 Random copolymerisation 21
2.3.2 Graft copolymerisation 24
2.3.3 Block copolymerisation 32
2.3.4 Epoxy resin-CTBN reaction 33
References 37
Chapter 3
CHARACTERISATION OF STRUCTURE
3.1 Optical Microscopy 39
vii
viii CONTENTS
3.2 Transmission Electron Microscopy 42
3.2.1 Replication . 42
3.2.2 Sectioning 43
3.2.3 Analysis of electron micrographs . 47
3.3 Scanning Electron Microscopy 48
3.4 Light Scattering 49
3.5 Coulter Counter 51
3.6 Gel Separation 52
3.7 The Secondary Glass Transition 56
3.7.1 Dynamic mechanical testing 56
3.7.2 Dielectric relaxation measurements 57
3.7.3 Differential scanning calorimetry . 58
3.7.4 Nuclear magnetic resonance 60
3.7.5 Comparison of techniques 61
3.8 Characterisation of Structure in Degraded Polymers 62
References 64
Chapter 4
MANUFACTURE OF TOUGHENED PLASTICS
4.1 Bulk and Bulk-Suspension Polymerisation of HIPS 66
4.1.1 Outline of process 67
4.1.2 Factors controlling structure 72
4.1.3 Commercial processes . 79
4.2 Manufacture of Toughened Epoxy Resins 82
4.3 Toughened Polypropylene 87
4.4 Emulsion Polymerisation-ABS Manufacture 90
4.4.1 Outline of process 90
4.4.2 Mechanism of emulsion polymerisation 92
4.4.3 Factors controlling structure 94
4.5 Blending 99
4.5.1 Blending directly with rubber 100
4.5.2 Blending with grafted rubbers 102
4.6 Comparison of Processes 102
References 105
Chapter 5
VISCOELASTIC PROPERTIES
5.1 Experimental Observations . 108
5.2 Models for Toughened Polymers . 116
CONTENTS ix
5.3 Mathematical Theories . 118
5.3.1 Bounds on moduli 119
5.3.2 Approximate equations 120
5.4 Application of Theories 122
5.5 Stress Analysis 126
5.5.1 Isolated spherical particle 126
5.5.2 Finite element analysis 129
5.5.3 Experimental methods 131
5.5.4 Thermal shrinkage stresses 133
5.6 Orientation 134
References 134
Chapter 6
DEFORMATION MECHANISMS IN GLASSY POLYMERS
6.1 Shear Yielding 137
6.1.1 Strain localisation· 137
6.1.2 Structure of shear bands 142
6.1.3 Shear band formation . 145
6.1.4 Criteria for shear yielding !50
6.2 Crazing 155
6.2.1 Structure of crazes !57
6.2.2 Craze formation !59
6.2.3 Properties of crazes 172
6.3 Interactions between Crazes and Shear Bands 177
References 180
Chapter 7
MECHANISMS OF RUBBER TOUGHENING
7.1 Statement of the Problem 182
7.2 Qualitative Theories of Toughening 188
7.2.1 Early theories 188
7.2.2 Multiple crazing theory 189
7.2.3 Shear yielding theories 191
7.2.4 Crazing with shear yielding 193
7.3 Volumetric Strain Measurements 195
7.4 Kinetics of Crazing 201
7.4.1 Crazing without interaction . 201
7.4.2 Crazing-shear interaction 205
7.5 Structure-Property Relationships . 206
7.5.1 Rubber particle size 207
7.5.2 Rubber-matrix adhesion 208
References 210
