Polymer Processing (2^nd Ed.)
Principles and Design

Fundamental concepts coupled with practical, step-by-step guidance

With its emphasis on core principles, this text equips readers with the skills and knowledge to design the many processes needed to safely and successfully manufacture thermoplastic parts. The first half of the text sets forth the general theory and concepts underlying polymer processing, such as the viscoelastic response of polymeric fluids and diffusion and mass transfer. Next, the text explores specific practical aspects of polymer processing, including mixing, extrusion dies, and post-die processing. By addressing a broad range of design issues and methods, the authors demonstrate how to solve most common processing problems.

This Second Edition of the highly acclaimed Polymer Processing has been thoroughly updated to reflect current polymer processing issues and practices. New areas of coverage include:

• Micro-injection molding to produce objects weighing a fraction of a gram, such as miniature gears and biomedical devices
• New chapter dedicated to the recycling of thermoplastics and the processing of renewable polymers
• Life-cycle assessment, a systematic method for determining whether recycling is appropriate and which form of recycling is optimal
• Rheology of polymers containing fibers

Chapters feature problem sets, enabling readers to assess and reinforce their knowledge as they progress through the text. There are also special design problems throughout the text that reflect real-world polymer processing issues. A companion website features numerical subroutines as well as guidance for using MATLAB^®, IMSL^®, and Excel to solve the sample problems from the text. By providing both underlying theory and practical step-by-step guidance, Polymer Processing is recommended for students in chemical, mechanical, materials, and polymer engineering.

Preface xi

Preface to the First Edition xiii

Acknowledgments xv

1 Importance of Process Design 1

1.1 Classification of Polymer Processes 1

1.2 Film Blowing: Case Study 5

1.3 Basics of Polymer Process Design 7

References 8

2 Isothermal Flow of Purely Viscous Non-Newtonian Fluids 9

Design Problem I Design of a Blow Molding Die 9

2.1 Viscous Behavior of Polymer Melts 10

2.2 One-Dimensional Isothermal Flows 13

2.2.1 Flow Through an Annular Die 14

2.2.2 Flow in a Wire Coating Die 17

2.3 Equations of Change for Isothermal Systems 19

2.4 Useful Approximations 26

2.5 Solution to Design Problem I 27

2.5.1 Lubrication Approximation Solution 27

2.5.2 Computer Solution 29

Problems 30

References 34

3 Viscoelastic Response of Polymeric Fluids and Fiber Suspensions 37

Design Problem II Design of a Parison Die for a Viscoelastic Fluid 37

3.1 Material Functions for Viscoelastic Fluids 38

3.1.1 Kinematics 38

3.1.2 Stress Tensor Components 39

3.1.3 Material Functions for Shear Flow 40

3.1.4 Shear-Free Flow Material Functions 43

3.2 Nonlinear Constitutive Equations 44

3.2.1 Description of Several Models 44

3.2.2 Fiber Suspensions 52

3.3 Rheometry 55

3.3.1 Shear Flow Measurements 56

3.3.2 Shear-Free Flow Measurements 58

3.4 Useful Relations for Material Functions 60

3.4.1 Effect of Molecular Weight 60

3.4.2 Relations Between Linear Viscoelastic Properties and Viscometric Functions 61

3.4.3 Branching 61

3.5 Rheological Measurements and Polymer Processability 62

3.6 Solution to Design Problem II 64

Problems 66

References 70

4 Diffusion and Mass Transfer 73

Design Problem III Design of a Dry-spinning System 73

4.1 Mass Transfer Fundamentals 74

4.1.1 Definitions of Concentrations and Velocities 74

4.1.2 Fluxes and Their Relationships 76

4.1.3 Fick’s First Law of Diffusion 76

4.1.4 Microscopic Material Balance 78

4.1.5 Similarity with Heat Transfer: Simple Applications 80

4.2 Diffusivity! Solubility! and Permeability in Polymer Systems 84

4.2.1 Diffusivity and Solubility of Simple Gases 84

4.2.2 Permeability of Simple Gases and Permachor 87

4.2.3 Moisture Sorption and Diffusion 90

4.2.4 Permeation of Higher-Activity Permeants 90

4.2.5 Polymer–Polymer Diffusion 93

4.2.6 Measurement Techniques and Their Mathematics 94

4.3 Non-Fickian Transport 95

4.4 Mass Transfer Coefficients 96

4.4.1 Definitions 96

4.4.2 Analogies Between Heat and Mass Transfer 97

4.5 Solution to Design Problem III 99

Problems 101

References 108

5 Nonisothermal Aspects of Polymer Processing 111

Design Problem IV Casting of Polypropylene Film 111

5.1 Temperature Effects on Rheological Properties 111

5.2 The Energy Equation 113

5.2.1 Shell Energy Balances 113

5.2.2 Equation of Thermal Energy 117

5.3 Thermal Transport Properties 120

5.3.1 Homogeneous Polymer Systems 120

5.3.2 Thermal Properties of Composite Systems 123

5.4 Heating and Cooling of Nondeforming Polymeric Materials 124

5.4.1 Transient Heat Conduction in Nondeforming Systems 125

5.4.2 Heat Transfer Coefficients 130

5.4.3 Radiation Heat Transfer 132

5.5 Crystallization! Morphology! and Orientation 135

5.5.1 Crystallization in the Quiescent State 136

5.5.2 Other Factors Affecting Crystallization 142

5.5.3 Polymer Molecular Orientation 143

5.6 Solution to Design Problem IV 145

Problems 147

References 150

6 Mixing 153

Design Problem V Design of a Multilayered Extrusion Die 153

6.1 Description of Mixing 154

6.2 Characterization of the State of Mixture 156

6.2.1 Statistical Description of Mixing 157

6.2.2 Scale and Intensity of Segregation 161

6.2.3 Mixing Measurement Techniques 163

6.3 Striation Thickness and Laminar Mixing 164

6.3.1 Striation Thickness Reduction from Geometrical Arguments 164

6.3.2 Striation Thickness Reduction from Kinematical Arguments 169

6.3.3 Laminar Mixing in Simple Geometries 171

6.4 Residence Time and Strain Distributions 174

6.4.1 Residence Time Distribution 174

6.4.2 Strain Distribution 177

6.5 Dispersive Mixing 180

6.5.1 Dispersion of Agglomerates 180

6.5.2 Liquid–Liquid Dispersion 182

6.6 Thermodynamics of Mixing 188

6.7 Chaotic Mixing 189

6.8 Solution to Design Problem V 191

Problems 194

References 198

7 Extrusion Dies 201

Design Problem VI Coextrusion Blow Molding Die 201

7.1 Extrudate Nonuniformities 202

7.2 Viscoelastic Phenomena 203

7.2.1 Flow Behavior in Contractions 203

7.2.2 Extrusion Instabilities 203

7.2.3 Die Swell 207

7.3 Sheet and Film Dies 212

7.4 Annular Dies 216

7.4.1 Center-Fed Annular Dies 216

7.4.2 Side-Fed and Spiral Mandrel Dies 217

7.4.3 Wire Coating Dies 217

7.5 Profile Extrusion Dies 220

7.6 Multiple Layer Extrusion 222

7.6.1 General Considerations 222

7.6.2 Design Equations 224

7.6.3 Flow Instabilities in Multiple Layer Flow 227

7.7 Solution to Design Problem VI 228

Problems 230

References 234

8 Extruders 235

Design Problem VII Design of a Devolatilization Section for a Single-screw Extruder 235

8.1 Description of Extruders 235

8.1.1 Single-Screw Extruders 237

8.1.2 Twin-Screw Extruders 238

8.2 Hopper Design 239

8.3 Plasticating Single-Screw Extruders 242

8.3.1 Solids Transport 242

8.3.2 Delay and Melting Zones 246

8.3.3 Metering Section 250

8.4 Twin-Screw Extruders 253

8.4.1 Self-wiping Corotating Twin-Screw Extruders 253

8.4.2 Intermeshing Counterrotating Extruders 256

8.5 Mixing! Devolatilization! and Reactions in Extruders 258

8.5.1 Mixing 258

8.5.2 Devolatilization in Extruders 262

8.5.3 Reactive Extrusion 264

8.6 Solution to Design Problem VII 265

8.6.1 Dimensional Analysis 265

8.6.2 Diffusion Theory 267

Problems 268

References 272

9 Postdie Processing 275

Design Problem VIII Design of a Film Blowing Process for Garbage Bags 275

9.1 Fiber Spinning 276

9.1.1 Isothermal Newtonian Model 278

9.1.2 Nonisothermal Newtonian Model 281

9.1.3 Isothermal Viscoelastic Model 285

9.1.4 High-Speed Spinning and Structure Formation 287

9.1.5 Instabilities in Fiber Spinning 290

9.2 Film Casting and Stretching 293

9.2.1 Film Casting 293

9.2.2 Stability of Film Casting 296

9.2.3 Film Stretching and Properties 297

9.3 Film Blowing 297

9.3.1 Isothermal Newtonian Model 299

9.3.2 Nonisothermal Newtonian Model 302

9.3.3 Nonisothermal Non-Newtonian Model 303

9.3.4 Biaxial Stretching and Mechanical Properties 304

9.3.5 Stability of Film Blowing 304

9.3.6 Scaleup 305

9.4 Solution to Design Problem VIII 305

Problems 306

References 308

10 Molding and Forming 311

Design Problem IX Design of a Compression Molding Process 311

10.1 Injection Molding 311

10.1.1 General Aspects of Injection Molding 311

10.1.2 Simulation of Injection Molding 315

10.1.3 Microinjection Molding 318

10.2 Compression Molding 319

10.2.1 General Aspects of Compression Molding 319

10.2.2 Simulation of Compression Molding 320

10.3 Thermoforming 322

10.3.1 General Aspects of Thermoforming 322

10.3.2 Modeling of Thermoforming 324

10.4 Blow Molding 328

10.4.1 Technological Aspects of Blow Molding 328

10.4.2 Simulation of Blow Molding 330

10.5 Solution to Design Problem IX 332

Problems 335

References 340

11 Process Engineering for Recycled and Renewable Polymers 343

11.1 Life-Cycle Assessment 343

11.2 Primary Recycling 348

11.3 Mechanical or Secondary Recycling 351

11.3.1 Rheology of Mixed Systems 352

11.3.2 Filtration 352

11.4 Tertiary or Feedstock Recycling 354

11.5 Renewable Polymers and Their Processability 357

11.5.1 Thermal Stability and Processing of Renewable Polymers 358

Problems 362

References 363

Nomenclature 365

Appendix A Rheological Data for Several Polymer Melts 373

Appendix B Physical Properties and Friction Coefficients for Some Common Polymers in the Bulk State 379

Appendix C Thermal Properties of Materials 381

Appendix D Conversion Table 385

Index 387

DONALD G. BAIRD, PhD, is the Alexander F. Giacco and Harry C. Wyatt Professor of Chemical Engineering at Virginia Tech. His research centers on the use of fundamental non-Newtonian fluid mechanics to develop improved processing operations for polymers and polymer composites. Among his many honors, the Society of Plastics Engineers has awarded him the International Award, the International Award for Research, and the International Award for Education. A holder of seven patents, Dr. Baird has published some 300 refereed publications.

DIMITRIS I. COLLIAS, PhD, is with the corporate R&D department of the Procter & Gamble Co. in Cincinnati, Ohio. He earned his PhD degree from Princeton University. With twenty years of industry experience in polymers, polymer processing, packaging, paper, and activated carbon, his current research focuses on developing renewable materials and processes for key products in the company’s portfolio. Dr. Collias holds fifty-four issued U.S. patents and is inventor or co-inventor in more than thirty U.S. patent applications.