Melt Rheology and Its Role in Plastics Processing

This book is designed to fulfill a dual role. On the one hand it provides a description of the rheological behavior of molten poly mers. On the other, it presents the role of rheology in melt processing operations. The account of rheology emphasises the underlying principles and presents results, but not detailed deriva tions of equations. The processing operations are described qualita tively, and wherever possible the role of rheology is discussed quantitatively. Little emphasis is given to non-rheological aspects of processes, for example, the design of machinery. The audience for which the book is intended is also dual in nature. It includes scientists and engineers whose work in the plastics industry requires some knowledge of aspects of rheology. Examples are the polymer synthetic chemist who is concerned with how a change in molecular weight will affect the melt viscosity and the extrusion engineer who needs to know the effects of a change in molecular weight distribution that might result from thermal degra dation. The audience also includes post-graduate students in polymer science and engineering who wish to acquire a more extensive background in rheology and perhaps become specialists in this area. Especially for the latter audience, references are given to more detailed accounts of specialized topics, such as constitutive relations and process simulations. Thus, the book could serve as a textbook for a graduate level course in polymer rheology, and it has been used for this purpose.

Texte du rabat
In this comprehensive book, plastics engineers, designers and manufacturers discover how to exploit the latest techniques of measuring the rheological properties of molten and viscoelastic plastics. The role of polymer rheology is fully examined in various melt processing operations, along with specialized areas.

Résumé
The audience also includes post-graduate students in polymer science and engineering who wish to acquire a more extensive background in rheology and perhaps become specialists in this area.

Contenu

1. Introduction to Rheology.- 1.1 What is Rheology?.- 1.2 Why Rheological Properties are Important.- 1.3 Stress as a Measure of Force.- 1.4 Strain as a Measure of Deformation.- 1.4.1 Strain Measures for Simple Extension.- 1.4.2 Shear Strain.- 1.5 Rheological Phenomena.- 1.5.1 Elasticity; Hooke's Law.- 1.5.2 Viscosity.- 1.5.3 Viscoelasticity.- 1.5.4 Structural Time Dependency.- 1.5.5 Plasticity and Yield Stress.- 1.6 Why Polymeric Liquids are Non-Newtonian.- 1.6.1 Polymer Solutions.- 1.6.2 Molten Plastics.- 1.7 A Word About Tensors.- 1.7.1 Vectors.- 1.7.2 What is a Tensor?.- 1.8 The Stress Tensor.- 1.9 A Strain Tensor for Infinitesimal Deformations.- 1.10 The Newtonian Fluid.- 1.11 The Basic Equations of Fluid Mechanics.- 1.11.1 The Continuity Equation.- 1.11.2 Cauchy's Equation.- 1.11.3 The Navier-Stokes Equation.- References.- 2. Linear Viscoelasticity.- 2.1 Introduction.- 2.2 The Relaxation Modulus.- 2.3 The Boltzmann Superposition Principle.- 2.4 Relaxation Modulus of Molten Polymers.- 2.5 Empirical Equations for the Relaxation Modulus.- 2.5.1 The Generalized Maxwell Model.- 2.5.2 Power Laws and an Exponential Function.- 2.6 The Relaxation Spectrum.- 2.7 Creep and Creep Recovery; The Compliance.- 2.8 Small Amplitude Oscillatory Shear.- 2.8.1 The Complex Modulus and the Complex Viscosity.- 2.8.2 Complex Modulus of Typical Molten Polymers.- 2.8.3 Quantitative Relationships between G*(?) and MWD.- 2.8.4 The Storage and Loss Compliances.- 2.9 Determination of Maxwell Model Parameters.- 2.10 Start-Up and Cessation of Steady Simple Shear and Extension.- 2.11 Molecular Theories: Prediction of Linear Behavior.- 2.11.1 The Modified Rouse Model for Unentangled Melts.- 2.11.1.1 The Rouse Model for Dilute Solutions.- 2.11.1.2 The Bueche Modification of the Rouse Theory.-2.11.1.3 The Bueche-Ferry Law.- 2.11.2 Molecular Theories for Entangled Melts.- 2.11.2.1 Evidence for the Existence of Entanglements.- 2.11.2.2 The Nature of Entanglement Coupling.- 2.11.2.3 Reptation.- 2.11.2.4 The Doi-Edwards Theory.- 2.11.2.5 The Curtiss-Bird Model.- 2.11.2.6 Limitations of Reptation Models.- 2.12 Time-Temperature Superposition.- 2.13 Linear Behavior of Several Polymers.- References.- 3. Introduction to Nonlinear Viscoelasticity.- 3.1 Introduction.- 3.2 Nonlinear Phenomena.- 3.3 Theories of Nonlinear Behavior.- 3.4 Finite Measures of Strain.- 3.4.1 The Cauchy Tensor and the Finger Tensor.- 3.4.2 Strain Tensors.- 3.4.3 Reference Configurations.- 3.4.4 Scalar Invariants of the Finger Tensor.- 3.5 The Rubberlike Liquid.- 3.5.1 A Theory of Finite Linear Viscoelasticity.- 3.5.2 Lodge's Network Theory and the Convected Maxwell Model.- 3.5.3 Behavior of the Rubberlike Liquid in Simple Shear Flows.- 3.5.3.1 Rubberlike Liquid in Step Shear Strain.- 3.5.3.2 Rubberlike Liquid in Steady Simple Shear.- 3.5.3.3 Rubberlike Liquid in Oscillatory Shear.- 3.5.3.4 Constrained Recoil of Rubberlike Liquid.- 3.5.3.5 The Stress Ratio (N1/?) and the Recoverable Shear.- 3.5.4 The Rubberlike Liquid in Simple Extension.- 3.5.5 Comments on the Rubberlike Liquid Model.- 3.6 The BKZ Equation.- 3.7 Wagner's Equation and the Damping Function.- 3.7.1 Strain Dependent Memory Function.- 3.7.2 Determination of the Damping Function.- 3.7.3 Separable Stress Relaxation Behavior.- 3.7.4 Damping Function Equations for Polymeric Liquids.- 3.7.4.1 Damping Function for Shear Flows.- 3.7.4.2 Damping Function for Simple Extension.- 3.7.4.3 Universal Damping Functions.- 3.7.5 Interpretation of the Damping Function in Terms of Entanglements.- 3.7.5.1 The Irreversibility Assumption.- 3.7.6Comments on the Use of the Damping Function.- 3.8 Molecular Models for Nonlinear Viscoelasticity.- 3.8.1 The Doi-Edwards Constitutive Equation.- 3.9 Strong Flows; The Tendency to Stretch and Align Molecules.- References.- 4. Steady Simple Shear Flow and the Viscometric Functions.- 4.1 Introduction.- 4.2 Steady Simple Shear Flow.- 4.3 Viscometric Flow.- 4.4 Wall Slip and Edge Effects.- 4.5 The Viscosity of Molten Polymers.- 4.5.1 Dependence of Viscosity on Shear Rate.- 4.5.2 Dependence of Viscosity on Temperature.- 4.6 The First Normal Stress Difference.- 4.7 Empirical Relationships Involving Viscometric Functions.- 4.7.1 The Cox-Merz Rules.- 4.7.2 The Gleissle Mirror Relations.- 4.7.3 Other Relationships.- References.- 5. Transient Shear Flows Used to Study Nonlinear Viscoelasticity.- 5.1 Introduction.- 5.2 Step Shear Strain.- 5.2.1 Finite Rise Time.- 5.2.2 The Nonlinear Shear Stress Relaxation Modulus.- 5.2.3 Time-Temperature Superposition.- 5.2.4 Strain-Dependent Spectrum and Maxwell Parameters.- 5.2.5 Normal Stress Differences for Single-Step Shear Strain.- 5.2.6 Multistep Strain Tests.- 5.3 Flows Involving Steady Simple Shear.- 5.3.1 Start-Up Flow.- 5.3.2 Cessation of Steady Simple Shear.- 5.3.3 Interrupted Shear.- 5.3.4 Reduction in Shear Rate.- 5.4 Nonlinear Creep.- 5.4.1 Time-Temperature Superposition of Creep Data.- 5.5 Recoil and Recoverable Shear.- 5.5.1 Creep Recovery.- 5.5.1.1 Time-Temperature Superposition; Creep Recovery.- 5.5.2 Recoil During Start-Up Flow.- 5.5.3 Recoverable Shear Following Steady Simple Shear.- 5.6 Superposed Deformations.- 5.6.1 Superposed Steady and Oscillatory Shear.- 5.6.2 Step Strain with Superposed Deformations.- 5.7 Large Amplitude Oscillatory Shear.- 5.8 Exponential Shear; A Strong Flow.- 5.9 Usefulness of Transient Shear Tests.- References.- 6. Extensional Flow Properties and Their Measurement.- 6.1 Introduction.- 6.2 Extensional Flows.- 6.3 Simple Extension.- 6.3.1 Material Functions for Simple Extension.- 6.3.2 Experimental Methods.- 6.3.3 Experimental Observations for LDPE.- 6.3.4 Experimental Observations for Linear Polymers.- 6.4 Biaxial Extension.- 6.5 Planar Extension.- 6.6 Other Extensional Flows.- References.- 7. Rotational and Sliding Surface Rheometers.- 7.1 Introduction.- 7.2 Sources of Error for Drag Flow Rheometers.- 7.2.1 Instru…