Mechanical Properties of Solid Polymers E-Book

Ian M. Ward

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 723

Veröffentlichungsjahr: 2012

Beschreibung

Providing an updated and comprehensive account of the properties of solid polymers, the book covers all aspects of mechanical behaviour.  This includes finite elastic behavior, linear viscoelasticity and mechanical relaxations, mechanical anisotropy, non-linear viscoelasicity, yield behavior and fracture. New to this edition is coverage of polymer nanocomposites, and molecular interpretations of yield, e.g. Bowden, Young, and Argon.

The book begins by focusing on the structure of polymers, including their chemical composition and physical structure.  It goes on to discuss the mechanical properties and behaviour of polymers, the statistical molecular theories of the rubber-like state and describes aspects of linear viscoelastic behaviour, its measurement, and experimental studies.

Later chapters cover composites and experimental behaviour, relaxation transitions, stress and yielding. The book concludes with a discussion of breaking phenomena.

Leseprobe

Contents

Cover

Title Page

Copyright

Preface

Chapter 1: Structure of Polymers

1.1 Chemical Composition

1.2 Physical Structure

References

Further Reading

Chapter 2: The Mechanical Properties of Polymers: General Considerations

2.1 Objectives

2.2 The Different Types of Mechanical Behaviour

2.3 The Elastic Solid and the Behaviour of Polymers

2.4 Stress and Strain

2.5 The Generalised Hooke's Law

References

Chapter 3: The Behaviour in the Rubber-Like State: Finite Strain Elasticity

3.1 The Generalised Definition of Strain

3.2 The Stress Tensor

3.3 The Stress–Strain Relationships

3.4 The Use of a Strain Energy Function

References

Chapter 4: Rubber-Like Elasticity

4.1 General Features of Rubber-Like Behaviour

4.2 The Thermodynamics of Deformation

4.3 The Statistical Theory

4.4 Modifications of Simple Molecular Theory

4.5 The Internal Energy Contribution to Rubber Elasticity

4.6 Conclusions

References

Further Reading

Chapter 5: Linear Viscoelastic Behaviour

5.1 Viscoelasticity as a Phenomenon

5.2 Mathematical Representation of Linear Viscoelasticity

5.3 Dynamical Mechanical Measurements: The Complex Modulus and Complex Compliance

5.4 The Relationships between the Complex Moduli and the Stress Relaxation Modulus

5.5 The Relaxation Strength

References

Further Reading

Chapter 6: The Measurement of Viscoelastic Behaviour

6.1 Creep and Stress Relaxation

6.2 Dynamic Mechanical Measurements

6.3 Wave-Propagation Methods

References

Further Reading

Chapter 7: Experimental Studies of Linear Viscoelastic Behaviour as a Function of Frequency and Temperature: Time–Temperature Equivalence

7.1 General Introduction

7.2 Time–Temperature Equivalence and Superposition

7.3 Transition State Theories

7.4 The Time–Temperature Equivalence of the Glass Transition Viscoelastic Behaviour in Amorphous Polymers and the Williams, Landel and Ferry (WLF) Equation

7.5 Normal Mode Theories Based on Motion of Isolated Flexible Chains

7.6 The Dynamics of Highly Entangled Polymers

References

Chapter 8: Anisotropic Mechanical Behaviour

8.1 The Description of Anisotropic Mechanical Behaviour

8.2 Mechanical Anisotropy in Polymers

8.3 Measurement of Elastic Constants

8.4 Experimental Studies of Mechanical Anisotropy in Oriented Polymers

8.5 Interpretation of Mechanical Anisotropy: General Considerations

8.6 Experimental Studies of Anisotropic Mechanical Behaviour and Their Interpretation

8.7 The Aggregate Model for Chain-Extended Polyethylene and Liquid Crystalline Polymers

8.8 Auxetic Materials: Negative Poisson's Ratio

References

Chapter 9: Polymer Composites: Macroscale and Microscale

9.1 Composites: A General Introduction

9.2 Mechanical Anisotropy of Polymer Composites

9.3 Short Fibre Composites

9.4 Nanocomposites

9.5 Takayanagi Models for Semi-Crystalline Polymers

9.6 Ultra-High-Modulus Polyethylene

9.7 Conclusions

References

Further Reading

Chapter 10: Relaxation Transitions: Experimental Behaviour and Molecular Interpretation

10.1 Amorphous Polymers: An Introduction

10.2 Factors Affecting the Glass Transition in Amorphous Polymers

10.3 Relaxation Transitions in Crystalline Polymers

10.4 Conclusions

References

Chapter 11: Non-linear Viscoelastic Behaviour

11.1 The Engineering Approach

11.2 The Rheological Approach

11.3 Creep and Stress Relaxation as Thermally Activated Processes

11.4 Multi-axial Deformation: Three-Dimensional Non-linear Viscoelasticity

References

Further Reading

Chapter 12: Yielding and Instability in Polymers

12.1 Discussion of the Load–Elongation Curves in Tensile Testing

12.2 Ideal Plastic Behaviour

12.3 Historical Development of Understanding of the Yield Process

12.4 Experimental Evidence for Yield Criteria in Polymers

12.5 The Molecular Interpretations of Yield

12.6 Cold-Drawing, Strain Hardening and the True Stress–Strain Curve

12.7 Shear Bands

12.8 Physical Considerations behind Viscoplastic Modelling

12.9 Shape Memory Polymers

References

Further Reading

Chapter 13: Breaking Phenomena

13.1 Definition of Tough and Brittle Behaviour in Polymers

13.2 Principles of Brittle Fracture of Polymers

13.3 Controlled Fracture in Brittle Polymers

13.4 Crazing in Glassy Polymers

13.5 The Structure and Formation of Crazes

13.6 Controlled Fracture in Tough Polymers

13.7 The Molecular Approach

13.8 Factors Influencing Brittle–Ductile Behaviour: Brittle–Ductile Transitions

13.9 The Impact Strength of Polymers

13.10 The Tensile Strength and Tearing of Polymers in the Rubbery State

13.11 Effect of Strain Rate and Temperature

13.12 Fatigue in Polymers

References

Further Reading

Index

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Library of Congress Cataloging-in-Publication Data

Ward, I. M. (Ian Macmillan), 1928– author. Mechanical properties of solid polymers. – Third edition / Ian M. Ward, School of Physics and Astronomy, Leeds University, Leeds, UK, John Sweeney, School of Engineering, Design and Technology, University of Bradford, Bradford, UK. pages cm Includes bibliographical references and index. ISBN 978-1-4443-1950-7 (hardback) 1. Polymers–Mechanical properties. I. Sweeney, J. (John) author II. Title. TA455.P58W37 2012 620.1′9204292–dc23 2012020163

A catalogue record for this book is available from the British Library.

Cloth ISBN: 9781444319507

Preface

This book is the third edition of Mechanical Properties of Solid Polymers and follows the format of the first two editions in writing the chapters as separate units. Therefore, each chapter can be regarded as a self-contained introduction and review of progress in the different aspects of the mechanical behaviour.

Since the publication of the second edition in 1983, the subject has advanced considerably in many respects, especially with regard to non-linear viscoelasticity, yield and fracture. We have altered some chapters very little, notably those dealing with viscoelastic behaviour and the earlier research on anisotropic mechanical behaviour and rubber elasticity, only adding sections to deal with the latest developments.

On the other hand, it has been necessary to change substantially the chapters on non-linear viscoelasticity, yield and fracture and in some cases incorporate material from the second edition of An Introduction to the Mechanical Properties of Solid Polymers. A separate chapter is also added on polymer composites.

In all cases, the approach of the previous textbooks has been followed. This is to obtain a formal description of the behaviour using the mathematical techniques of solid mechanics, followed by an attempt to seek understanding in terms of the molecular structure and morphology.

Finally, we wish to thank Margaret Ward for undertaking a substantial part of the initial typing of the new text and Glenys Bowles for providing secretarial assistance.

I. M. Ward J. Sweeney

2

The Mechanical Properties of Polymers: General Considerations

2.1 Objectives

Discussions of the mechanical properties of solid polymers often contain two inter-related objectives. The first of these is to obtain an adequate macroscopic description of the particular facet of polymer behaviour under consideration. The second objective is to seek an explanation of this behaviour in molecular terms, which may include details of the chemical composition and physical structure. In this book, we will endeavour, where possible, to separate these two objectives and, in particular, to establish a satisfactory macroscopic or phenomenological description before discussing molecular interpretations.

This should make it clear that many of the established relationships are purely descriptive, and do not necessarily have any implications with regard to an interpretation in structural terms. For engineering applications of polymers this is sufficient, because a description of the mechanical behaviour under conditions that simulate their end use is often all that is required, together with empirical information concerning their method of manufacture.

2.2 The Different Types of Mechanical Behaviour

It is difficult to classify polymers as particular types of materials such as a glassy solid or a viscous liquid, since their mechanical properties are so dependent on the conditions of testing, for example the rate of application of load, temperature and amount of strain.

A polymer can show all the features of a glassy, brittle solid or an elastic rubber or a viscous liquid depending on the temperature and time scale of measurement. Polymers are usually described as viscoelastic materials, a generic term which emphasises their intermediate position between viscous liquids and elastic solids. At low temperatures, or high frequencies of measurement, a polymer may be glass-like with a Young's modulus of 1–10 GPa and will break or flow at strains greater than 5%. At high temperatures or low frequencies, the same polymer may be rubber-like with a modulus of 1–10 MPa, withstanding large extensions (~100%) without permanent deformation. At still higher temperatures, permanent deformation occurs under load, and the polymer behaves like a highly viscous liquid.

In an intermediate temperature or frequency range, commonly called the glass transition range, the polymer is neither glassy nor rubber-like. It shows an intermediate modulus, is viscoelastic and may dissipate a considerable amount of energy on being strained. The glass transition manifests itself in several ways, for example by a change in the volume coefficient of expansion, which can be used to define a glass transition temperature . The glass transition is central to a great deal of the mechanical behaviour of polymers for two reasons. First there are the attempts to link the time–temperature equivalence of viscoelastic behaviour with the glass transition temperature . Secondly, glass transitions can be studied at a molecular level by such techniques as nuclear magnetic resonance and dielectric relaxation. In this way, it is possible to gain an understanding of the molecular origins of the viscoelasticity.