Thermoplastic and Rubber Compounds - Technology and Physical Chemistry

360 Pages·2008·9.054 MB·360\360

by  White, James L., Kim, Kwang-Jea

James L. White
Kwang-Jea Kim
Thermoplastic
and Rubber Compounds
Technology and Physical Chemistry
Carl Hanser Publishers, Munich • Hanser Gardner Publications, Cincinnati
The Authors:
Prof. Dr. James L. White, The University of Akron, 250 South Forge Street, Akron, OH, 44325-0301, USA
Dr. Kwang-Jea Kim, The University of Akron, 250 South Forge Street, Akron, OH, 44325-0301, USA
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Library of Congress Cataloging-in-Publication Data
White, James Lindsay, 1938-
Thermoplastic and rubber compounds : technology and physical chemistry /
James L. White, Kwang-Jea Kim.
p. cm.
ISBN-13: 978-1-56990-407-7 (hardcover)
ISBN-10: 1-56990-407-3 (hardcover)
1. Thermoplastics. 2. Rubber. I. Kim, Kwang-Jea, 1962- II. Title.
TA455.P5W495 2007
668.4‘23--dc22
2007011924
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ISBN 978-3-446-40980-4
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Preface
All commercial polymers are compounds that have additives primarily intended as stabilizers.
These additives protect the polymer from oxygen, heat, and other aspects of the environment.
Many available polymer products are compounds that involve a wide range of ingredients,
including commercial products such as polypropylene-based thermoplastic elastomers,
polyvinyl chloride pipes, mineral-fi lled polypropylene, and pneumatic tire components.
These compounds contain not only stabilizers but also other polymers, fi llers, oils, curatives,
accelerators (for curatives), and other ingredients.
The compounding of polymers is not a new technology. It dates back to the beginnings of
the rubber industry in the fi rst half of the nineteenth century. Compounding is discussed
extensively in the memoirs of Charles Goodyear and Thomas Hancock, both published in
1855–1857. These early efforts were almost entirely empirical. Today, roughly 150 years later,
there is a sound scientifi c understanding of most modern additives’ mechanisms in their
intended applications.
As the polymer products industry developed and became increasingly large in this period,
compound recipes became much more complex and sophisticated. Separate compounding
cultures developed for individual polymer types, such as elastomers, polyvinyl chloride,
polyolefi ns and thermoplastic elastomers. Indeed, sub-cultures, such as tire rubber com-
pounds, specialty elastomer compounds, polyethylene compounds, and polypropylene
compounds, have come into existence. The rubber industry has also in large part separated
and become isolated from the thermoplastics industry.
Recipes have generally been designed on the basis of considering each active ingredient
independently and presuming these ingredients do not interact. This often turns out not
to be the case. When the number of components becomes three or more, unexpected
consequences often result. A polar solvent or additive introduced into a binary polymer blend
will incorporate itself preferentially into the more-polar polymer rather than the less-polar
polymer. An additive previously compounded into a particular polymer can migrate into a
second polymer during mixing as the number of components in a blend increases.
It is our purpose in this book to describe the components and composition of major types
of polymer compounds used in both the thermoplastics and rubber industries. We will
describe the intended mechanisms of these additives and their sometimes unintended various
interactions with one another.
This book is divided into nine chapters. Chapter 1 describes the composition of polymer
compounds and the chemical nature and physical properties of ingredients. Chapters 2
through 5 describe binary compounds of polymers with solid particles (Chapter 2), solvents
(polymer solutions) (Chapter 3), additives such as stabilizers and curatives (Chapter 4), and
a second polymer (blends) (Chapter 5). We turn to ternary compounds in Chapters 6 and
7. Chapter 6 discusses polymers with two low molecular weight liquids, two polymers with
one low molecular weight substance, and three polymers including compatibilized polymer
VIII Preface
blends. Chapter 7 considers the combination of polymer, solid particles, and low molecular
weight additives including curatives and accelerators. Chapter 8 considers multicomponent
compounds and the component interactions. Chapter 9 considers the mixing machinery
and mixing cycles used for preparation of compounds. We discuss both the technology and
basic mechanisms of the major commercial batch and continuous mixers, as well as related
areas such as reactive mixing.
For readers with special interest in rubber and rubber compounding, we recommend especially
sections 1.3 to 1.9; 2.4; 3.3, 3.8 to 3.10; 4.2 to 4.4, 4.7, 4.11; 5.2 to 5.6; 6.2, 6.4, 6.5, 6.8; 7.2 to
7.5; 8.3, 8.5; 9.2 to 9.4.
For readers with special interest in thermoplastics we recommend especially sections 1.3,
1.4, 1.6, 1.7; 2.4; 3.3 to 3.5, 3.11; 4.2, 4.3, 4.5 to 4.11; 5.1 to 5.11; 6.3 to 6.9; 7.2 to 7.4; 8.4, 8.6;
9.3 to 9.5.
2007
J. L. White, K. J. Kim
Contents
Preface ........................................................................ VII
1 Overview and Compound Ingredients .......................................... 1
1.1 Introduction ............................................................. 1
1.2 Philosophy of Polymer Compounds ........................................ 1
1.3 Polymers ................................................................ 4
1.3.1 Homopolymers .................................................... 4
1.3.2 Copolymers ....................................................... 8
1.3.2.1 General ................................................... 8
1.3.2.2 Butadiene Copolymers ..................................... 9
1.3.2.3 Ethylene-Olefi n Copolymers ............................... 11
1.3.3 Molecular Weight Distribution ..................................... 12
1.3.4 Transition Behavior ............................................... 13
1.3.5 Melt Rheological Properties ........................................ 15
1.3.6 Mechanical Behavior .............................................. 22
1.4 Particle Fillers and Reinforcements ........................................ 23
1.4.1 General .......................................................... 23
1.4.2 Carbon Black ..................................................... 24
1.4.3 Calcium Carbonate ............................................... 27
1.4.4 Zinc Oxide (ZnO) ................................................ 29
1.4.5 Titanium Dioxide ................................................. 31
1.4.6 Silica ............................................................ 31
1.4.7 Talc and Mica .................................................... 36
1.4.8 Kaolin Clays ...................................................... 39
1.4.9 Fibrous Silicates and Wollastonite................................... 41
1.4.10 Glass Fibers ...................................................... 43
1.4.11 Glass Spheres ..................................................... 43
1.4.12 Organic Fillers .................................................... 44
1.4.12.1 Cellulose and Cellulose Fibers .............................. 45
1.4.12.2 Starch ................................................... 51
1.4.12.3 Aramid Fibers ............................................ 52
1.4.12.4 Carbon Fibers ............................................ 53
1.4.13 Nanofi llers ....................................................... 53
1.4.13.1 Montmorillonite .......................................... 53
1.4.13.2 Carbon Nanotubes ........................................ 54
1.5 Oils and Plasticizers ..................................................... 55
1.6 Antidegradents.......................................................... 56
1.7 Processing Aids ......................................................... 57
1.8 Curatives ............................................................... 60
1.9 Accelerators ............................................................ 62
X Contents
2 Polymer-Particle Filler Systems ............................................... 73
2.1 Introduction ............................................................ 73
2.2 Particle Properties and Interaction ........................................ 73
2.2.1 Particle Density ................................................... 73
2.2.2 Particle Size ...................................................... 75
2.2.3 Particle Shape .................................................... 77
2.3 Hydrodynamic Theory of Suspensions ..................................... 78
2.3.1 General .......................................................... 78
2.3.2 Spheres .......................................................... 79
2.3.3 Ellipsoids ........................................................ 80
2.3.4 Interacting Particles ............................................... 81
2.3.5 Continuum Theories .............................................. 81
2.4 Experimental Studies of Compound Properties ............................. 82
2.4.1 Large Spheres .................................................... 82
2.4.2 Large Fibers and Ellipsoids ......................................... 83
2.4.2.1 Fluids ................................................... 83
2.4.2.2 Solids .................................................... 85
2.4.3 Carbon Black ..................................................... 89
2.4.3.1 Thermoplastic Melts/Uncured Compounds .................. 89
2.4.3.2 Rubber Vulcanizates ....................................... 91
2.4.4 Calcium Carbonate (CaCO ) ....................................... 93
3
2.4.4.1 Thermoplastic Melts ...................................... 93
2.4.4.2 Solid Thermoplastics ...................................... 95
2.4.5 Silica ............................................................ 96
2.4.5.1 Uncured Rubber Compounds .............................. 96
2.4.5.2 Rubber Vulcanizates ....................................... 96
2.4.6 Talc and Mica .................................................... 96
2.4.6.1 Thermoplastic Melts ...................................... 96
2.4.6.2 Solid Polymers ........................................... 98
2.4.7 Montmorillonite and Organo Clays (Nano Composites) .............. 98
2.4.8 Carbon Nano-Tubes .............................................. 99
2.5 Summary ..............................................................100
3 Polymer Solutions and Swollen Vulcanizates ..................................105
3.1 Introduction ...........................................................105
3.2 Low Molecular Weight Solutions .........................................105
3.3 Thermodynamics of Polymer Solutions: Flexible Chains ....................110
3.4 Solubility of Crystalline Polymers ........................................112
3.5 Solutions of Rigid Chain Polymers .......................................113
3.6 Thermodynamics of Heterogeneous Flexible Chain Polymer Solutions .......114
3.7 Phase Separation and Equilibrium .......................................114
3.8 Swelling of Vulcanizates .................................................117
3.9 Rheological Properties of Polymer Solutions ..............................118
3.10 Oil-Extended Rubber ...................................................122
Contents XI
3.11 Plasticized Polyvinyl Chloride ...........................................123
3.12 Summary ..............................................................124
4 Polymer Additive Binary Systems ............................................129
4.1 Introduction ...........................................................129
4.2 Solubility of Additives ..................................................129
4.3 Antioxidants ...........................................................131
4.3.1 General .........................................................131
4.3.2 Mechanism of Oxidation .........................................132
4.3.3 Antioxidant Mechanisms .........................................133
4.3.4 Antioxidant Miscibility ...........................................133
4.3.5 Antioxidant Migration ...........................................134
4.4 Antiozonants ..........................................................136
4.5 Light Stabilizers ........................................................137
4.6 Heat Stabilizers ........................................................138
4.7 Processing Aids ........................................................140
4.8 Surface Property Modifi ers ..............................................144
4.9 Antistatic Additives .....................................................144
4.10 Nucleating Agents ......................................................145
4.11 Curatives ..............................................................147
4.11.1 Sulfur Crosslinking ..............................................147
4.11.2 Crosslinking by Organic Peroxides .................................148
4.11.3 Crosslinking by Metallic Oxides ...................................149
4.11.4 Crosslinking by Phenolic Derivatives ...............................149
4.11.5 Crosslinking by High Energy Radiation ............................149
4.12 Summary ..............................................................152
5 Binary Polymer Blends ......................................................157
5.1 Introduction ...........................................................157
5.2 Thermodynamics of Polymer-Polymer Miscibility .........................157
5.3 Statistical Thermodynamic Interpretation .................................159
5.4 Miscible Polymer Blends ................................................160
5.5 Partial Miscibility ......................................................164
5.6 Problems With Copolymers .............................................166
5.7 Immiscible Polymer Blends and Interfacial Tension ........................167
5.8 Phase Morphology in Immiscible Binary Polymer Blends ...................173
5.9 Special Polymer Melt Phase Distributions .................................175
5.10 Mechanical Properties of Binary Polymer Blends ..........................177
5.11 Blends of Recycled Polymers .............................................177
6 Ternary Systems:
Polymer Blends plus Liquid Additives and Compatibilizing Agents .............181
6.1 Introduction ...........................................................181
6.2 Ternary Low Molecular Weight Systems ...................................181
XII Contents
6.3 Polymer Plus Two Low Molecular Weight Liquids ..........................183
6.4 Low Molecular Weight Oils/Additives in Binary Polymer Blends .............186
6.5 Amphiphilic Molecules and Block Graft Copolymers in Immiscible Polymer
Blends (Compatibilized Blends)..........................................190
6.6 Mechanical Properties of Compatibilized Blends ...........................192
6.7 Compatibilized Recycled Polymer Blends .................................194
6.8 High Impact Polystyrene (HIPS) .........................................194
6.9 Ternary Polymer Blends .................................................195
6.10 Summary ..............................................................195
7 Polymer-Filler-Additives and Curative-Accelerator Compounds ................201
7.1 Introduction ...........................................................201
7.2 Mineral Fillers: Carboxylic Acid-Polymer .................................201
7.3 Organic-Silane Coupling Agent for Thermosets, Thermoplastics, and
Rubber ................................................................203
7.4 Organo Clay Nanocomposites (Clay-Organic Amine-Polymer) ..............205
7.5 Rubber-Sulfur-Accelerator ..............................................207
7.6 Crosslinking by Enzymes ................................................208
7.7 Particle Filler with Two Polymers ........................................208
8 Multicomponent Compounds ...............................................213
8.1 Introduction ...........................................................213
8.2 Simple Multicomponent Compounds ....................................213
8.3 Tire Compounds .......................................................214
8.3.1 Polydiene-Carbon Black Oil Compounds ...........................214
8.3.2 Polydiene-Rubber-Silica Compounds ..............................215
8.4 Thermoplastic Compounds .............................................216
8.4.1 Polyvinyl Chloride Compounds ...................................216
8.4.2 Isotactic Polypropylene Compounds ...............................217
8.4.3 Recycled Polymer Blend Compounds ..............................218
8.5 Rubber Compounds with Special Mechanical Properties ....................219
8.5.1 Chlorinated Butyl Rubber Compounds .............................219
8.5.2 Nitrile Rubber Compounds .......................................222
8.5.3 Ethylene-Propylene-Diene Terpolymer (EPDM) Compounds .........224
8.6 Thermoplastic Elastomer (TPE) Compounds..............................225
8.6.1 Elastomer-Modifi ed Polypropylene ................................225
8.6.2 SBS-Type Thermoplastic Elastomer ................................225
9 Mixing Machinery: Batch and Continuous ....................................229
9.1 Introduction ...........................................................229
9.2 Batch Mixers ...........................................................229
9.2.1 Mills ...........................................................229
9.2.2 Open Batch Mixers. ..............................................230
9.2.3 Internal Mixers: Non-Intermeshing Rotors .........................234
Contents XIII
9.2.3.1 Technology .............................................234
9.2.3.2 Basic Studies ............................................243
9.2.4 Internal Mixers: Intermeshing .....................................246
9.2.4.1 Technology .............................................246
9.2.4.2 Basic Studies ............................................247
9.2.5 Internal Mixer Cycles .............................................247
9.3 Continuous Mixers .....................................................249
9.3.1 Single-Screw Extruders ...........................................249
9.3.2 List (Buss-Coperion) Kokneters/Kneaders ..........................249
9.3.2.1 Technology .............................................249
9.3.2.2 Basic Studies ............................................251
9.3.3 Intermeshing Modular Co-Rotating Twin-Screw Extruders ...........252
9.3.3.1 Technology .............................................252
9.3.3.2 Basic Studies ............................................255
9.3.4 Intermeshing Modular Counter-Rotating Twin-Screw Extruders ......257
9.3.4.1 Technology .............................................257
9.3.4.2 Basic Studies ............................................259
9.3.5 Tangential Modular Counter-Rotating Twin-Screw Extruders .........260
9.3.5.1 Technology .............................................260
9.3.5.2 Basic Studies ............................................260
9.3.6 Continuous Mixers ..............................................261
9.3.6.1 Technology .............................................261
9.3.6.2 Basic Studies ............................................262
9.3.7 The Strategy of Adding Ingredients During Continuous Mixing.......264
9.4 Comparison of Commercial Mixing Machines.............................264
9.4.1 Batch Internal Mixers vs. Continuous Mixers .......................264
9.4.2 Comparison of Continuous Mixing Machines ......................265
9.5 Reactive Extrusion......................................................265
9.5.1 Polymer Modifi cation and Grafting Reactions .......................265
9.5.2 Polymerization ..................................................266
Subject Index ..................................................................275
Author Index ..................................................................309
1 Overview and Compound Ingredients
1.1 Introduction
Polymers are generally not used commercially in a pure or “neat” state. Rather, commercial
polymeric materials contain a wide range of added ingredients intended to enhance their
properties. Such properties might include chemical stability, mechanical behavior, and/or
processability.
Compounds are pervasive in the polymer industry. Indeed, even presumably neat polymers are
compounds containing antidegradents, which are antioxidants and/or anti-ozonants. These
additives are small polar molecules. In more complex compounds there are in addition other
polymers, reinforcing fi llers, oils, curatives, and accelerators, which are intended to crosslink
polymers. These are also small, usually polar, molecules. This chapter is about the philosophy
of the polymer compound and the characteristics of their various ingredients.
1.2 Philosophy of Polymer Compounds
Generally, neat polymers are not adequate for the applications intended for customer use.
This inadequacy is usually associated with insuffi cient chemical resistance against attacks of
oxygen, ozone, and heat. They may also possess insuffi cient modulus, hardness, or toughness.
Another common problem is insuffi cient creep resistance in the basic polymer.
Polymers need to be modifi ed to meet the customer’s requirements. There are various ways
to improve the polymer properties to accomplish this: the blending of two or more polymers,
the addition of various fi llers, or the inclusion of antidegradation agents. Each polymer, fi ller,
or other additive has a different chemical structure.
From reading the two classical volumes Thomas Hancock’s 1857 Origin and Progress [1] and
Charles Goodyear’s 1855 Gum Elastic [2], it is clear that compounding dates to the beginning
of the rubber industry in Europe and the United States. The concept of compounds and
compounding, however, precedes the synthetic polymer industry. It certainly was part of the
ancient and medieval ceramics and metals industries. Indeed, the different cuisines of the
various cultures of the world representing the tastes of their inhabitants are really examples
of distinctive compounding.
A typical polymer compound has the ingredients:
• Polymers
• Filler/reinforcing particles
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