Analyzing and Troubleshooting Single-Screw Extrusion

9783446432666%2Efm......Page 1
Preface......Page 6
Acknowledgements......Page 8
Contents......Page 10
1 Single-Screw Extrusion: Introduction and Troubleshooting......Page 21
1.1 Organization of this Book......Page 23
1.2 Troubleshooting Extrusion Processes......Page 25
1.3 Introduction to Screw Geometry......Page 26
1.3.1 Screw Geometric Quantitative Characteristics......Page 28
1.4 Simple Flow Equations for the Metering Section......Page 31
1.5.1 Example 1: Calculation of Rotational and Pressure Flow Components......Page 35
1.5.2 Example 2: Flow Calculations for a Properly Operating Extruder......Page 37
1.5.3 Example 3: Flow Calculations for an Improperly Operating Extruder......Page 38
Nomenclature......Page 40
References......Page 42
2 Polymer Materials......Page 43
2.1 Introduction and History......Page 44
2.1.1 History of Natural Polymers......Page 45
2.1.2 The History of Synthetic Polymers......Page 46
2.2 Characteristics of Synthetic Polymers......Page 48
2.3 Structure Effects on Properties......Page 51
2.3.1 Stereochemistry......Page 54
2.3.2 Melting and Glass Transition Temperatures......Page 55
2.3.3 Crystallinity......Page 57
2.4.1 Condensation Reactions......Page 60
2.4.2 Addition Reactions......Page 63
2.5 Polymer Degradation......Page 66
2.5.1 Ceiling Temperature......Page 69
2.5.2 Degradation of Vinyl Polymers......Page 71
2.5.3 Degradation of Condensation Polymers......Page 73
References......Page 74
3.1 Introduction to the Deformation of Materials......Page 76
3.2 Introduction to Basic Concepts of Molecular Size......Page 77
3.2.1 Size Distribution Example......Page 78
3.2.2 Molecular Weight Distributions for Polymers......Page 79
3.3 Basic Rheology Concepts......Page 82
3.4 Polymer Solution Viscosity and Polymer Molecular Weight......Page 86
3.4.1 Sample Calculation of Solution Viscosity......Page 90
3.5 Introduction to Viscoelasticity......Page 91
3.6.1 Capillary Rheometers......Page 99
3.6.2 Cone and Plate Rheometers......Page 110
3.6.3 Melt Index and Melt Flow Rate......Page 113
3.7 Viscosity of Polymers as Functions of Molecular Character, Temperature, and Pressure......Page 116
3.8 Models for Non-Newtonian Flow......Page 122
Nomenclature......Page 124
References......Page 126
4 Resin Physical Properties Related to Processing......Page 128
4.1 Bulk Density and Compaction......Page 129
4.1.1 Measurement of Bulk Density......Page 130
4.1.2 Measuring the Compaction Characteristics of a Resin......Page 131
4.2 Lateral Stress Ratio......Page 134
4.2.1 Measuring the Lateral Stress Ratio......Page 135
4.3 Stress at a Sliding Interface......Page 137
4.3.1 The Screw Simulator and the Measurement of the Stress at the Interface......Page 138
4.4 Melting Flux......Page 140
4.5 Heat Capacity......Page 142
4.6 Thermal Conductivity and Heat Transfer......Page 143
4.7 Melt Density......Page 144
References......Page 146
5 Solids Conveying......Page 149
5.1 Description of the Solid Conveying Process......Page 150
5.2 Literature Review of Smooth-Bore Solids Conveying Models......Page 152
5.2.1 Darnell and Mol Model......Page 155
5.2.2 Tadmor and Klein Model......Page 156
5.2.3 Clarkson University Models......Page 157
5.2.4 Hyun and Spalding Model......Page 160
5.3 Modern Experimental Solids Conveying Devices......Page 161
5.3.1 Solids Conveying Devices at Clarkson University......Page 162
5.3.2 The Solids Conveying Device at Dow......Page 176
5.4 Comparison of the Modified Campbell-Dontula Model with Experimental Data......Page 186
5.4.1 Solids Conveying Example Calculation......Page 190
5.5 Grooved Bore Solids Conveying......Page 192
5.5.1 Grooved Barrel Solids Conveying Models......Page 196
5.6 Solids Conveying Notes......Page 198
Nomenclature......Page 201
References......Page 203
6 The Melting Process......Page 207
6.1 Compression Ratio and Compression Rate......Page 209
6.2 The Melting Process......Page 211
6.2.1 The Melting Process as a Function of Screw Geometry......Page 212
6.2.2 Review of the Classical Literature......Page 217
6.2.3 Reevaluation of the Tadmor and Klein Melting Data......Page 218
6.3 Theory Development for Melting Using Screw Rotation Physics......Page 221
6.3.1 Melting Model for a Conventional Transition Section Using Screw Rotation Physics......Page 222
6.3.2 Melting Models for Barrier Screw Sections......Page 236
6.4 Effect of Pressure on Melting Rate......Page 245
6.5 One-Dimensional Melting......Page 246
6.5.1 One-Dimensional Melting Model......Page 250
6.6 Solid Bed Breakup......Page 252
6.7 Melting Section Characteristics......Page 256
Nomenclature......Page 258
References......Page 260
7.1 Introduction to the Reference Frame......Page 264
7.2 Laboratory Observations......Page 267
7.3 Literature Survey......Page 271
7.4 Development of Linearized Flow Analysis......Page 276
7.4.1 Example Flow Calculation......Page 291
7.5 Numerical Flow Evaluation......Page 294
7.5.1 Simulation of a 500 mm Diameter Melt-Fed Extruder......Page 296
7.5.2 Extrusion Variables and Errors......Page 298
7.5.3 Corrections to Rotational Flow......Page 304
7.5.4 Simulation of the 500 mm Diameter Extruder Using Fc......Page 309
7.6 Frame Dependent Variables......Page 310
7.6.1 Example Calculation of Energy Dissipation......Page 313
7.7 Viscous Energy Dissipation and Temperature of the Resin in the Channel......Page 314
7.7.1 Energy Dissipation and Channel Temperature for Screw Rotation......Page 320
7.7.2 Energy Dissipation and Channel Temperature for Barrel Rotation......Page 324
7.7.3 Temperature Increase Calculation Example for a Screw Pump......Page 325
7.7.4 Heat Transfer Coefficients......Page 330
7.7.5 Temperature Calculation Using a Control Volume Technique......Page 331
7.7.6 Numerical Comparison of Temperatures for Screw and Barrel Rotations......Page 334
7.8 Metering Section Characteristics......Page 336
Nomenclature......Page 338
References......Page 342
8 Mixing Processes for Single-Screw Extruders......Page 346
8.1 Common Mixing Operations for Single-Screw Extruders......Page 347
8.1.1 Common Mixing Applications......Page 348
8.2 Dispersive and Distributive Mixing Processes......Page 350
8.3 Fundamentals of Mixing......Page 352
8.3.1 Measures of Mixing......Page 353
8.3.2 Experimental Demonstration of Mixing......Page 355
8.4 The Melting Process as the Primary Mechanism for Mixing......Page 363
8.4.1 Experimental Analysis of the Melting and Mixing Capacity of a Screw......Page 366
8.4.2 Mixing and Barrier-Flighted Melting Sections......Page 369
8.5 Secondary Mixing Processes and Devices......Page 370
8.5.1 Maddock-Style Mixers......Page 371
8.5.2 Blister Ring Mixers......Page 376
8.5.3 Spiral Dam Mixers......Page 378
8.5.4 Pin-Type Mixers......Page 379
8.5.5 Knob Mixers......Page 380
8.5.7 Dynamic Mixers......Page 381
8.5.8 Static Mixers......Page 384
8.6 Mixing Using Natural Resins and Masterbatches......Page 391
8.7 Mixing and Melting Performance as a Function of Flight Clearance......Page 392
8.9 Effect of Discharge Pressure on Mixing......Page 393
8.10 Shear Refinement......Page 394
8.11 Direct Compounding Using Single-Screw Extruders......Page 396
Nomenclature......Page 397
References......Page 399
9 Scaling of Single-Screw Extrusion Processes......Page 404
9.1 Scaling Rules......Page 405
9.2 Engineering Design Method for Plasticating Screws......Page 406
9.3 Scale-Up from a 40 mm Diameter Extruder to an 80 mm Diameter Machine for a PE Resin......Page 410
9.4 Rate Increase for an 88.9 mm Diameter Extruder Running a HIPS Resin......Page 414
Nomenclature......Page 421
References......Page 422
10 Introduction to Troubleshooting the Extrusion Process......Page 424
10.1 The Troubleshooting Process......Page 425
10.2 Hypothesis Setting and Problem Solving......Page 428
10.2.1 Case Study for the Design of a New Resin......Page 429
10.2.2 Case Study for a Surface Blemish......Page 431
10.2.3 Case Study for a Profile Extrusion Process......Page 432
10.3 Equipment and Tools Needed for Troubleshooting......Page 433
10.3.1 Maddock Solidification Experiment......Page 435
10.4.1 Flight Clearance and Hard Facing......Page 436
10.4.2 Barrel and Screw Alignment......Page 438
10.4.3 Extruder Barrel Supports......Page 439
10.4.4 First-Time Installation of a Screw......Page 441
10.4.5 Screw Breaks......Page 442
10.4.6 Protection from High-Pressure Events......Page 444
10.4.8 Particle Seals and Viscoseals......Page 446
10.5 Common Electrical and Sensor Problems......Page 448
10.5.2 Pressure Sensors......Page 449
10.5.3 Electronic Filters and Noise......Page 450
10.6 Motors and Drive Systems......Page 452
10.6.1 Motor Efficiencies and Power Factors......Page 454
10.7 Typical Screw Channel Dimensions......Page 455
10.8.1 Energy Dissipated by the Screw......Page 456
10.8.2 Screw Geometry Indices......Page 457
10.9 Barrel Temperature Optimization......Page 459
10.10 Screw Temperature Profile......Page 462
10.11 The Screw Manufacturing and Refurbishing Process......Page 471
10.12 Injection-Molding Plasticators......Page 479
10.13 New Equipment Installations......Page 481
10.13.1 Case Study: A Large Diameter Extruder Purchase......Page 485
10.13.2 Case Study: Extruder and Line Purchase for a New Product......Page 486
10.13.3 Summary for New Equipment Installations......Page 487
Nomenclature......Page 488
References......Page 490
11.1 Foreign Contaminants in the Extrudate......Page 493
11.1.1 Melt Filtration......Page 494
11.1.2 Metal Fragments in the Extrudate......Page 498
11.1.3 Gas Bubbles in a New Sheet Line......Page 499
11.2 Gels in Polyolefin Resins......Page 500
11.2.1 Protocols for Gel Analysis......Page 501
11.3 Resin Decomposition in Stagnant Regions of a Process......Page 507
11.4 Improper Shutdown of Processing Equipment......Page 509
11.5 Equipment Purging......Page 510
11.7 Flight Radii Size......Page 512
11.8 Drying the Resin......Page 515
11.9 Color Masterbatches......Page 516
11.10.1 Intermittent Crosslinked Gels in a Film Product......Page 517
11.10.2 Small Gels in an LLDPE Film Product......Page 523
11.10.3 Degassing Holes in Blow-Molded Bottles......Page 526
11.11.1 Splay Defects for Injection-Molded Parts......Page 529
11.12.1 Injection-Molded Parts with Splay and Poor Resin Color Purge......Page 532
11.12.2 Black Color Streaks in Molded Parts: Case One......Page 536
11.12.3 Black Streaks in Molded Parts: Case Two......Page 541
11.12.4 Silver Streaks in a Clear GPPS Resin Injection-Molded Packaging Part......Page 545
11.12.5 The Injection-Molding Problem at Saturn......Page 552
Nomenclature......Page 553
References......Page 554
12 Flow Surging......Page 557
12.1.1 Relationship Between Discharge Pressure and Rate at the Die......Page 558
12.2 Troubleshooting Flow Surging Processes......Page 559
12.3 Barrel Zone and Screw Temperature Control......Page 560
12.3.1 Water- and Air-Cooled Barrel Zones......Page 561
12.4 Rotation- and Geometry-Induced Pressure Oscillations......Page 562
12.5 Gear Pump Control......Page 564
12.7.1 Poor Barrel Zone Temperature Control......Page 567
12.7.2 Optimization of Barrel Temperatures for Improved Solids Conveying......Page 570
12.7.3 Flow Surging Due to High Temperatures in the Feed Section of the Screw......Page 572
12.7.4 Flow Surging Due to High Temperatures in the Feed Casing......Page 579
12.7.5 Flow Surging Due to a Poorly Designed Barrier Entry for GPPS Resin......Page 581
12.7.6 Solid Blockage at the Entry of a Spiral Mixer......Page 584
12.7.7 Flow Surging Caused by a Worn Feed Casing and a New Barrel......Page 590
12.7.8 Flow Surging for a PC Resin Extrusion Process......Page 599
Nomenclature......Page 603
References......Page 604
13 Rate-Limited Extrusion Processes......Page 606
13.1 Vent Flow for Multiple-Stage Extruders......Page 608
13.2 Screw Wear......Page 610
13.4.1 Rate Limitation Due to a Worn Screw......Page 612
13.4.2 Rate Limitation Due to Solid Polymer Fragments in the Extrudate......Page 613
13.4.3 Rate Limited by the Discharge Temperature for a Pelletizing Extruder......Page 618
13.4.4 Large Diameter Extruder Running PS Resin......Page 625
13.4.5 Rate Limited by Discharge Temperature and Torque for Starch Extrusion......Page 629
13.4.6 Vent Flow for a Two-Stage Screw Running a Low Bulk Density PS Feedstock......Page 632
13.4.7 Increasing the Rate of a Large Part Blow-Molding Process......Page 634
Nomenclature......Page 638
References......Page 639
14 Barrier and High-Performance Screws......Page 640
14.1 Barrier Screws......Page 642
14.2.1 Double Wave Screw......Page 648
14.2.2 Energy Transfer Screws......Page 650
14.2.3 Variable Barrier Energy Transfer Screws......Page 656
14.2.4 Distributive Melt Mixing Screws......Page 660
14.2.5 Fusion Screws......Page 664
14.3.1 Stratablend Screws......Page 665
14.3.2 Unimix Screws......Page 667
Nomenclature......Page 668
References......Page 669
15.1 Simulation Methods......Page 672
15.2 Compounding Processes......Page 673
15.2.1 Common Problems for Melt-Fed Extruders on Compounding Lines......Page 675
15.3 Large-Diameter Pumping Extruders......Page 676
15.3.1 Loss of Rate Due to Poor Material Conveyance in the Feed Section......Page 685
15.3.2 Operation of the Slide Valve......Page 687
15.3.3 Nitrogen Inerting on Vent Domes......Page 688
15.4 Secondary Extruders for Tandem Foam Sheet Lines......Page 689
15.4.1 High-Performance Cooling Screws......Page 693
Nomenclature......Page 696
References......Page 697
Appendix A1 Polymer Abbreviation Definitions......Page 699
A3.1 Capillary Rheometer......Page 701
A3.2 Cone and Plate Rheometer......Page 705
References......Page 707
A4.1 Shear Stress at a Sliding Interface for Select Resins......Page 709
A4.2 Melting Fluxes for Select Resins......Page 713
References......Page 716
A5.1 Channel Dimensions, Assumptions, and Basic Force Balances......Page 719
A5.2 Campbell-Dontula Model......Page 721
A5.2.1 Modified Campbell-Dontula Model......Page 722
A5.3 Hyun-Spalding Model......Page 724
A5.4 Yamamuro-Penumadu-Campbell Model......Page 726
A5.6 The Complete Dow Solids Conveying Data Set......Page 728
References......Page 733
A6.1 Derivation of the Melting Performance Equations for a Conventional Channel......Page 735
References......Page 746
A7.1 Transformed Frame Flow Analysis......Page 747
A7.1.1 x-Directional Flow......Page 749
A7.1.2 z-Directional Flow......Page 750
A7.1.3 z-Directional Flow for Helix Rotation with a Stationary Screw Core and Barrel......Page 756
A7.1.4 z-Directional Flow Due to a Pressure Gradient......Page 758
A7.2.1 Viscous Energy Dissipation for Screw Rotation: Generalized Solution......Page 763
A7.2.2 Viscous Energy Dissipation for Screw Rotation for Channels with Small Aspect Ratios (H/W < 0.1)......Page 769
A7.3 Viscous Energy Dissipation for Barrel Rotation......Page 771
A7.3.1 Viscous Energy Dissipation for Barrel Rotation: Generalized Solution......Page 772
A7.3.2 Viscous Energy Dissipation for Barrel Rotation for Channels with Small Aspect Ratios (H/W < 0.1)......Page 775
References......Page 776
Author......Page 777
Subject......Page 783