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Preface to the Fifth Edition
6
1 Introduction
18
1.1 Basic Process
18
1.2 Scope of the Book
19
1.3 General Literature Survey
20
1.4 History of Polymer Extrusion
23
Part I – Extrusion Machinery
28
2 Different Types of Extruders
30
2.1 The Single Screw Extruder
30
2.1.1 Basic Operation
32
2.1.2 Vented Extruders
33
2.1.3 Rubber Extruders
34
2.1.4 High-Speed Extrusion
39
2.1.4.1 Melt Temperature
39
2.1.4.2 Extruders without Gear Reducer
40
2.1.4.3 Energy Consumption
40
2.1.4.4 Change-over Resin Consumption
40
2.1.4.5 Change-over Time and Residence Time
41
2.2 The Multiscrew Extruder
41
2.2.1 The Twin Screw Extruder
41
2.2.2 The Multiscrew Extruder With More Than Two Screws
42
2.2.3 The Gear Pump Extruder
44
2.3 Disk Extruders
45
2.3.1 Viscous Drag Disk Extruders
45
2.3.1.1 Stepped Disk Extruder
45
2.3.1.2 Drum Extruder
47
2.3.1.3 Spiral Disk Extruder
48
2.3.1.4 Diskpack Extruder
48
2.3.2 The Elastic Melt Extruder
52
2.3.3 Overview of Disk Extruders
53
2.4 Ram Extruders
53
2.4.1 Single Ram Extruders
54
2.4.1.1 Solid State Extrusion
55
2.4.2 Multi Ram Extruder
58
2.4.3 Appendix 2.1
59
2.4.3.1 Pumping Efficiency in Diskpack Extruder
59
3 Extruder Hardware
66
3.1 Extruder Drive
66
3.1.1 AC Motor Drive System
66
3.1.1.1 Mechanical Adjustable Speed Drive
67
3.1.1.2 Electric Friction Clutch Drive
67
3.1.1.3 Adjustable Frequency Drive
68
3.1.2 DC Motor Drive System
70
3.1.2.1 Brushless DC Drives
72
3.1.3 Hydraulic Drive System
72
3.1.4 Comparison of Various Drive Systems
75
3.1.5 Reducer
76
3.1.6 Constant Torque Characteristics
77
3.2 Thrust Bearing Assembly
78
3.3 Barrel and Feed Throat
81
3.4 Feed Hopper
85
3.5 Extruder Screw
87
3.6 Die Assembly
89
3.6.1 Screens and Screen Changers
89
3.7 Heating and Cooling Systems
92
3.7.1 Electric Heating
92
3.7.1.1 Resistance Heating
92
3.7.1.2 Induction Heating
93
3.7.2 Fluid Heating
94
3.7.3 Extruder Cooling
94
3.7.4 Screw Heating and Cooling
97
4 Instrumentation and Control
102
4.1 Instrumentation Requirements
102
4.1.1 Most Important Parameters
103
4.2 Pressure Measurement
104
4.2.1 The Importance of Melt Pressure
104
4.2.2 Different Types of Pressure Transducers
105
4.2.3 Mechanical Considerations
109
4.2.4 Specifications
110
4.2.5 Comparisons of Different Transducers
113
4.3 Temperature Measurement
113
4.3.1 Methods of Temperature Measurement
114
4.3.2 Barrel Temperature Measurement
117
4.3.3 Stock Temperature Measurement
119
4.3.3.1 Ultrasound Transmission Time
122
4.3.3.2 Infrared Melt Temperature Measurement
123
4.4 Other Measurements
124
4.4.1 Power Measurement
124
4.4.2 Rotational Speed
126
4.4.3 Extrudate Thickness
127
4.4.4 Extrudate Surface Conditions
131
4.5 Temperature Control
133
4.5.1 On-Off Control
134
4.5.2 Proportional Control
136
4.5.2.1 Proportional-Only Control
136
4.5.2.2 Proportional and Integral Control
140
4.5.2.3 Proportional and Integral and Derivative Control
141
4.5.2.4 Dual Sensor Temperature Control
142
4.5.3 Controllers
143
4.5.3.1 Temperature Controllers
143
4.5.3.2 Power Controllers
143
4.5.3.3 Dual Output Controllers
145
4.5.4 Time-Temperature Characteristics
145
4.5.4.1 Thermal Characteristics of the System
145
4.5.4.2 Modeling of Response in Linear Systems
147
4.5.4.3 Temperature Characteristics with On-Off Control
150
4.5.5 Tuning of the Controller Parameters
152
4.5.5.1 Performance Criteria
152
4.5.5.2 Effect of PID Parameters
153
4.5.5.3 Tuning Procedure When Process Model Is Unknown
154
4.5.5.4 Tuning Procedure When Process Model Is Known
155
4.5.5.5 Pre-Tuned Temperature Controllers
156
4.5.5.6 Self-Tuning Temperature Controllers
157
4.6 Total Process Control
157
4.6.1 True Total Extrusion Process Control
158
Part II – Process Analysis
164
5 Fundamental Principles
166
5.1 Balance Equations
166
5.1.1 The Mass Balance Equation
166
5.1.2 The Momentum Balance Equation
167
5.1.3 The Energy Balance Equation
168
5.2 Basic Thermodynamics
170
5.2.1 Rubber Elasticity
174
5.2.2 Strain-Induced Crystallization
176
5.3 Heat Transfer
177
5.3.1 Conductive Heat Transfer
177
5.3.2 Convective Heat Transfer
178
5.3.3 Dimensionless Numbers
178
5.3.3.1 Dimensional Analysis
178
5.3.3.2 Important Dimensionless Numbers
180
5.3.4 Viscous Heat Generation
185
5.3.5 Radiative Heat Transport
186
5.3.5.1 Dielectric Heating
188
5.3.5.2 Microwave Heating
190
5.4 Basics of Devolatilization
192
5.4.1 Devolatilization of Particulate Polymer
197
5.4.2 Devolatilization of Polymer Melts
198
Appendix 5.1
202
Example: Pipe Flow of Newtonian Fluid
202
6 Important Polymer Properties
208
6.1 Properties of Bulk Materials
208
6.1.1 Bulk Density
208
6.1.2 Coefficient of Friction
211
6.1.3 Particle Size and Shape
217
6.1.4 Other Properties
218
6.2 Melt Flow Properties
219
6.2.1 Basic Definitions
219
6.2.2 Power Law Fluid
225
6.2.3 Other Fluid Models
230
6.2.4 Effect of Temperature and Pressure
231
6.2.5 Viscoelastic Behavior
235
6.2.6 Measurement of Flow Properties
237
6.2.6.1 Capillary Rheometer
237
6.2.6.2 Melt Index Tester
240
6.2.6.3 Cone and Plate Rheometer
244
6.2.6.4 Slit Die Rheometer
245
6.2.6.5 Dynamic Analysis
247
6.3 Thermal Properties
250
6.3.1 Thermal Conductivity
251
6.3.2 Specific Volume and Morphology
253
6.3.3 Specific Heat and Heat of Fusion
256
6.3.4 Specific Enthalpy
258
6.3.5 Thermal Diffusivity
259
6.3.6 Melting Point
262
6.3.7 Induction Time
262
6.3.8 Thermal Characterization
264
6.3.8.1 DTA and DSC
264
6.3.8.2 TGA
264
6.3.8.3 TMA
265
6.3.8.4 Other Thermal Characterization Techniques
265
6.4 Polymer Property Summary
265
7 Functional Process Analysis
272
7.1 Basic Screw Geometry
272
7.2 Solids Conveying
275
7.2.1 Gravity Induced Solids Conveying
276
7.2.1.1 Pressure Distribution
279
7.2.1.2 Flow Rate
282
7.2.1.3 Design Criteria
283
7.2.2 Drag Induced Solids Conveying
285
7.2.2.1 Frictional Heat Generation
299
7.2.2.2 Grooved Barrel Sections
301
7.2.2.3 Adjustable Grooved Barrel Extruders
313
7.2.2.4 Starve Feeding Versus Flood Feeding
319
7.3 Plasticating
322
7.3.1 Theoretical Model of Contiguous Solids Melting
323
7.3.1.1 Non-Newtonian, Non-Isothermal Case
333
7.3.2 Other Melting Models
343
7.3.3 Power Consumption in the Melting Zone
347
7.3.4 Computer Simulation
349
7.3.5 Dispersed Solids Melting
350
7.4 Melt Conveying
357
7.4.1 Newtonian Fluids
360
7.4.1.1 Effect of Flight Flanks
365
7.4.1.2 Effect of Clearance
367
7.4.1.3 Power Consumption in Melt Conveying
370
7.4.2 Power Law Fluids
373
7.4.2.1 One-Dimensional Flow
373
7.4.2.2 Two-Dimensional Flow
378
7.4.3 Non-Isothermal Analysis
384
7.4.3.1 Newtonian Fluids with Negligible Viscous Dissipation
384
7.4.3.2 Non-Isothermal Analysis of Power Law Fluids
391
7.4.3.3 Developing Temperatures
404
7.4.3.4 Estimating Fully Developed Melt Temperatures
421
7.4.3.5 Assumption of Stationary Screw and Rotating Barrel
428
7.5 Die Forming
436
7.5.1 Velocity and Temperature Profiles
437
7.5.2 Extrudate Swell
446
7.5.3 Die Flow Instabilities
448
7.5.3.1 Shark Skin
448
7.5.3.2 Melt Fracture
449
7.5.3.3 Draw Resonance
451
7.6 Devolatilization
452
7.7 Mixing
458
7.7.1 Mixing in Screw Extruders
459
7.7.1.1 Distributive Mixing in Screw Extruders
464
7.7.2 Static Mixing Devices
474
7.7.2.1 Geometry of Static Mixers
477
7.7.2.2 Functional Performance Characteristics
481
7.7.2.3 Miscellaneous Considerations
485
7.7.3 Dispersive Mixing
486
7.7.3.1 Solid-Liquid Systems
486
7.7.3.2 Liquid-Liquid System
488
7.7.4 Backmixing
500
7.7.4.1 Cross-Sectional Mixing and Axial Mixing
500
7.7.4.2 Residence Time Distribution
502
7.7.4.3 RTD in Screw Extruders
504
7.7.4.4 Methods to Improve Backmixing
505
7.7.4.5 Conclusions for Backmixing
507
Appendix 7.1
508
Appendix 7.2
509
Appendix 7.3
510
8 Extruder Screw Design
526
8.1 Mechanical Considerations
527
8.1.1 Torsional Strength of the Screw Root
527
8.1.2 Strength of the Screw Flight
529
8.1.3 Lateral Deflection of the Screw
531
8.2 Optimizing for Output
536
8.2.1 Optimizing for Melt Conveying
536
8.2.2 Optimizing for Plasticating
547
8.2.2.1 Effect of Helix Angle
549
8.2.2.2 Effect of Multiple Flights
549
8.2.2.3 Effect of Flight Clearance
551
8.2.2.4 Effect of Compression Ratio
553
8.2.3 Optimizing for Solids Conveying
554
8.2.3.1 Effect of Channel Depth
554
8.2.3.2 Effect of Helix Angle
555
8.2.3.3 Effect of Number of Flights
556
8.2.3.4 Effect of Flight Clearance
556
8.2.3.5 Effect of Flight Geometry
556
8.3 Optimizing for Power Consumption
557
8.3.1 Optimum Helix Angle
558
8.3.2 Effect of Flight Clearance
560
8.3.3 Effect of Flight Width
561
8.4 Single-Flighted Extruder Screws
565
8.4.1 The Standard Extruder Screw
566
8.4.2 Modifications of the Standard Extruder Screw
567
8.5 Devolatilizing Extruder Screws
570
8.5.1 Functional Design Considerations
571
8.5.2 Various Vented Extruder Screw Designs
575
8.5.2.1 Conventional Vented Extruder Screw
575
8.5.2.2 Bypass Vented Extruder Screw
576
8.5.2.3 Rearward Devolatilization
577
8.5.2.4 Multi-Vent Devolatilization
578
8.5.2.5 Cascade Devolatilization
579
8.5.2.6 Venting through the Screw
580
8.5.2.7 Venting through a Flighted Barrel
581
8.5.3 Vent Port Configuration
582
8.6 Multi-Flighted Extruder Screws
585
8.6.1 The Conventional Multi-Flighted Extruder Screw
585
8.6.2 Barrier Flight Extruder Screws
586
8.6.2.1 The Maillefer Screw
589
8.6.2.2 The Barr Screw
592
8.6.2.3 The Dray and Lawrence Screw
595
8.6.2.4 The Kim Screw
596
8.6.2.5 The Ingen Housz Screw
597
8.6.2.6 The CRD Barrier Screw
598
8.6.2.7 Summary of Barrier Screws
599
8.7 Mixing Screws
601
8.7.1 Dispersive Mixing Elements
601
8.7.1.1 The CRD Mixer
619
8.7.1.2 Mixers to Break Up the Solid Bed
633
8.7.1.3 Summary of Dispersive Mixers
635
8.7.2 Distributive Mixing Elements
636
8.7.2.1 Ring or Sleeve Mixers
638
8.7.2.2 Variable Depth Mixers
639
8.7.2.3 Summary of Distributive Mixers
640
8.8 Efficient Extrusion of Medical Devices
641
8.8.1 Introduction
641
8.8.2 Good Manufacturing Practices in Medical Extrusion
642
8.8.3 Automation of the Medical Extrusion Process
642
8.8.4 Minimizing Polymer Degradation
643
8.8.5 Melt Temperatures Inside the Extruder
643
8.8.6 Melt Temperatures and Screw Design
644
8.8.7 Molecular Degradation and Screw Design
647
8.8.8 Conclusions
651
8.9 Scale-Up
652
8.9.1 Common Scale-Up Factors
652
8.9.2 Scale-Up for Heat Transfer
655
8.9.3 Scale-Up for Mixing
656
8.9.4 Comparison of Various Scale-Up Methods
657
8.10 Rebuilding Worn Screws and Barrels
659
8.10.1 Application of Hardfacing Materials
661
8.10.1.1 Oxyacetylene Welding
661
8.10.1.2 Tungsten Inert Gas Welding
662
8.10.1.3 Plasma Transfer Arc Welding
662
8.10.1.4 Metal Inert Gas Welding
663
8.10.1.5 Laser Hardfacing
663
8.10.2 Rebuilding of Extruder Barrels
663
9 Die Design
670
9.1 Basic Considerations
671
9.1.1 Balancing the Die by Adjusting the Land Length
672
9.1.2 Balancing by Channel Height
676
9.1.3 Other Methods of Die Balancing
679
9.2 Film and Sheet Dies
680
9.2.1 Flow Adjustment in Sheet and Film Dies
681
9.2.2 The Horseshoe Die
684
9.3 Pipe and Tubing Dies
685
9.3.1 Tooling Design for Tubing
688
9.3.1.1 Definitions of Various Draw Ratios
689
9.3.1.2 Land Length
690
9.3.1.3 Taper Angles
691
9.3.1.4 Special Features
693
9.4 Blown Film Dies
693
9.4.1 The Spiral Mandrel Geometry
696
9.4.2 Effect of Die Geometry on Flow Distribution
697
9.4.3 Summary of Spiral Mandrel Die Design Variables
701
9.5 Profile Extrusion Dies
701
9.6 Coextrusion
703
9.6.1 Interface Distortion
707
9.7 Calibrators
709
10 Twin Screw Extruders
714
10.1 Introduction
714
10.2 Twin versus Single Screw Extruder
716
10.3 Intermeshing Co-Rotating Extruders
718
10.3.1 Closely Intermeshing Extruders
718
10.3.2 Self-Wiping Extruders
721
10.3.2.1 Geometry of Self-Wiping Extruders
722
10.3.2.2 Conveying in Self-Wiping Extruders
730
10.4 Intermeshing Counter-Rotating Extruders
737
10.5 Non-Intermeshing Twin Screw Extruders
747
10.6 Coaxial Twin Screw Extruders
760
10.7 Devolatilization in Twin Screw Extruders
762
10.8 Commercial Twin Screw Extruders
766
10.8.1 Screw Design Issues for Co-Rotating Twin Screw Extruders
770
10.8.2 Scale-Up in Co-Rotating Twin Screw Extruders
773
10.9 Overview of Twin Screw Extruders
775
11 Troubleshooting Extruders
780
11.1 Requirements for Efficient Troubleshooting
780
11.1.1 Instrumentation
781
11.1.2 Understanding of the Extrusion Process
781
11.1.3 Collect and Analyze Historical Data (Timeline)
782
11.1.4 Team Building
783
11.1.5 Condition of the Equipment
783
11.1.6 Information on the Feedstock
784
11.2 Tools for Troubleshooting
785
11.2.1 Temperature Measurement Devices
785
11.2.2 Data Acquisition Systems (DAS)
786
11.2.2.1 Portable Data Collectors/Machine Analyzers
786
11.2.2.2 Fixed Station Data Acquisition Systems
787
11.2.3 Light Microscopy
789
11.2.4 Thermochromic Materials
790
11.2.5 Thermal Analysis
792
11.2.6 Miscellaneous Tools
792
11.3 Systematic Troubleshooting
793
11.3.1 Upsets versus Development Problems
793
11.3.2 Machine-Related Problems
793
11.3.2.1 Drive System
793
11.3.2.2 The Feed System
795
11.3.2.3 Different Feeding Systems
795
11.3.2.4 Heating and Cooling System
795
11.3.2.5 Wear Problems
797
11.3.2.6 Screw Binding
814
11.3.3 Polymer Degradation
820
11.3.3.1 Types of Degradation
820
11.3.3.2 Degradation in Extrusion
824
11.3.4 Extrusion Instabilities
837
11.3.4.1 Frequency of Instability
838
11.3.4.2 Functional Instabilities
845
11.3.4.3 Solving Extrusion Instabilities
850
11.3.5 Air Entrapment
851
11.3.6 Gels, Gel Content, and Gelation
853
11.3.6.1 Measuring Gels
856
11.3.6.2 Gels Created in the Extrusion Process
857
11.3.6.3 Removing Gels Produced in Polymerization
858
11.3.7 Die Flow Problems
860
11.3.7.1 Melt Fracture
860
11.3.7.2 Die Lip Build-Up (Die Drool)
862
11.3.7.3 V- or W-Patterns
863
11.3.7.4 Specks and Discoloration
863
11.3.7.5 Lines in Extruded Product
868
11.3.7.6 Optical Properties
870
12 Modeling and Simulation of the Extrusion Process
878
12.1 Introduction
878
12.2 Background
879
12.2.1 Analytical Techniques
879
12.2.2 Numerical Methods
881
12.2.2.1 Finite Difference Method
882
12.2.2.2 Finite Element Method
883
12.2.2.3 Boundary Element Method
884
12.2.3 Remeshing Techniques in Moving Boundary Problems
885
12.2.4 Rheology
887
12.3 Simulating 3-D Flows with 2-D Models
888
12.3.1 Simulating Flows in Internal Batch Mixers with 2-D Models
888
12.3.2 Simulating Flows in Extrusion with 2-D Models
894
12.3.3 Simulating Flows in Extrusion Dies with 2-D Models
898
12.4 Three-Dimensional Simulation
902
12.4.1 Simulating Flows in the Banbury Mixer with Three-Dimensional Models
902
12.4.2 Simulating Flows in Extrusion Dies with 3-Dimensional Models
904
12.4.3 Simulating Flows in Extrusion with 3-Dimensional Models
909
12.4.3.1 Regular Conveying Screw
909
12.4.3.2 Energy Transfer Mixer
910
12.4.3.3 Twin Screw Extruder
912
12.4.3.4 Rhomboidal Mixers and Fluted Mixers (Leroy/Maddock)
918
12.4.3.5 Turbo-Screw
923
12.4.3.6 CRD Mixer
925
12.4.4 Static Mixers
927
12.5 Conclusions
929
Conversion Constants
936
Length
936
Volume
936
Mass
937
Density
937
Force
937
Stress
938
Viscosity
938
Energy/.Work
939
Power
939
Specific Energy
939
Thermal Conductivity
940
Temperature
940
Index
942
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