Leseprobe

zu

„Understanding Extrusion“

von Chris Rauwendaal

ISBN (Buch): 978-1-56990-698-9

ISBN (E-Book): 978-1-56990-699-6

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fachbuch.de/buch/Understanding+Extrusion/9783446416864

sowie im Buchhandel

© Carl Hanser Verlag, München

https://www.hanser-fachbuch.de/buch/Understanding+Extrusion/9783446416864https://www.hanser-fachbuch.de/buch/Understanding+Extrusion/9783446416864

The first edition of Understanding Extrusion was published in 2000 and the second edition in 2010. Since the second edition was issued several important develop-ments have taken place. As a result, it makes sense to have a third edition of Under-standing Extrusion.Most of the new material is incorporated in Chapter 2. Topics included in this chapter are interpretation of extrusion process data, dimensional variation by melt temperature fluctuations, efficient extrusion, and more. Chapters 7 and 8 have also been extended and now cover topics such as analysis of shrink void formation and grooved barrel extruder technology.I would like to thank Dr. Mark Smith for his encouragement to work on this third edition. I also want to thank my wife Sietske for her continued support and for put-ting up with me despite these time-consuming projects.

Chris RauwendaalSeptember 2018

Preface to the Third Edition

Preface to the Third Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V

1 Extrusion Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 What is an Extruder? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Different Types of Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.1 Single Screw Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.2 Twin Screw Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.2.1 Co-Rotating Twin Screw Extruders . . . . . . . . . . . . . . . . . 21.2.2.2 Counter-Rotating Twin Screw Extruders . . . . . . . . . . . . 3

1.2.3 Ram Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.3 Components of an Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.3.1 The Extruder Screw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3.2 The Extruder Barrel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3.3 The Feed Throat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.3.4 The Feed Hopper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3.5 Barrel Heating and Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3.6 Screw Heating and Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.3.7 The Breaker Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.3.8 The Screen Pack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.3.8.1 Screen Changers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.3.9 The Extrusion Die . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.3.9.1 Coextrusion Dies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.3.10 The Extruder Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.3.10.1 Coupling between Motor and Gearbox . . . . . . . . . . . . . . 151.3.11 The Speed Reducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.3.11.1 Thrust Bearing Assembly . . . . . . . . . . . . . . . . . . . . . . . . 161.3.12 The Gear Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2 Instrumentation and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.1 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.2 Most Important Process Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.2.1 Melt Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202.2.2 Pressure Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Contents

VIII  Contents

2.2.3 Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.2.4 Melt Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 232.2.5 Barrel Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.3 Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.3.1 On-Off Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.3.2 Proportional Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.3.3 Fuzzy Logic Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.4 Collection and Interpretation of Extrusion Process Data . . . . . . . . . . . . . 292.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292.4.2 Vital Signs of the Extrusion Process . . . . . . . . . . . . . . . . . . . . . . . 29

2.4.2.1 Melt Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302.4.2.2 Melt Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352.4.2.3 Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

2.4.3 Examples of Extrusion Problems Solved by Using a Data Acquisition System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442.4.3.1 Variation in Stock Temperature . . . . . . . . . . . . . . . . . . . 442.4.3.2 Variation in Feed Housing Temperature . . . . . . . . . . . . 462.4.3.3 Variation in Melt Pressure . . . . . . . . . . . . . . . . . . . . . . . . 48

2.4.4 Process Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502.4.5 Temperature-Induced Dimensional Changes of Extrudate . . . . . 50

3 Complete Extrusion Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533.1 Tubing and Pipe Extrusion Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533.2 Film and Sheet Lines Using the Roll Stack Process . . . . . . . . . . . . . . . . . 543.3 Film Lines Using Chill Roll Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553.4 Combination of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

3.4.1 Coextrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563.4.2 Extrusion Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573.4.3 Extrusion Lamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

3.5 Blown Film Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593.6 Extrusion Compounding Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593.7 Profile Extrusion Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4 Plastics and Their Properties Important in Extrusion . . . . . . . . . . . . . 634.1 Thermoplastics and Thermosets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634.2 Amorphous and Semi-Crystalline Plastics . . . . . . . . . . . . . . . . . . . . . . . . . 644.3 Liquid Crystalline Plastics (LCPs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664.4 Elastomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664.5 Flow Behavior of Plastic Melts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674.6 Melt Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684.7 The Effect of Shearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694.8 Shear Thinning or Pseudoplastic Behavior . . . . . . . . . . . . . . . . . . . . . . . . 69

Contents  IX

4.9 Effect of Temperature on Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704.10 Viscous Heat Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714.11 Thermal Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

4.11.1 Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724.11.2 Specific Heat and Enthalpy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724.11.3 Thermal Stability and Induction Time . . . . . . . . . . . . . . . . . . . . . . 734.11.4 Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 744.11.5 Melting Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764.11.6 Glass Transition Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

5 How an Extruder Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775.1 Solids Conveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

5.1.1 Gravity Induced Conveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 785.1.2 Drag Induced Conveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 815.1.3 Starve Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825.1.4 Grooved Feed Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.2 Melting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855.2.1 Contiguous Solids Melting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855.2.2 Dispersed Solids Melting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

5.3 Melt Conveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895.3.1 Melt Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

5.4 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 935.4.1 Distributive Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 935.4.2 Mixing Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

5.4.2.1 Distributive Mixing Sections . . . . . . . . . . . . . . . . . . . . . . 985.4.2.2 Dispersive Mixing Sections . . . . . . . . . . . . . . . . . . . . . . . 102

5.5 Degassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085.6 Die Forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

5.6.1 Size and Shape Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1115.6.2 Tubing and Pipe Dies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145.6.3 Flat Film and Sheet Dies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1175.6.4 Profile Dies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

6 How to Run an Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236.2 Before Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236.3 Getting Ready for a Run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1246.4 Starting the Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266.5 Actual Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286.6 Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

6.6.1 Purging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296.7 Safety Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

6.7.1 Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

X  Contents

6.7.2 Moving Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1316.7.3 Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1326.7.4 Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1326.7.5 Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

6.8 Inspection and Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

7 How to Troubleshoot Extrusion Problems . . . . . . . . . . . . . . . . . . . . . . . 1377.1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1377.2 Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

7.2.1 Good Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1377.2.2 Good Understanding of the Process . . . . . . . . . . . . . . . . . . . . . . . . 1387.2.3 Collect and Analyze Historical Data . . . . . . . . . . . . . . . . . . . . . . . 1387.2.4 Teamwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

7.3 Main Types of Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1397.3.1 Output Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

7.3.1.1 Low Extruder Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1397.3.1.2 Variation in Extruder Output . . . . . . . . . . . . . . . . . . . . . 141

7.3.2 Appearance Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1447.3.2.1 Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1457.3.2.2 Die Drool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1457.3.2.3 Discoloration and Degradation . . . . . . . . . . . . . . . . . . . . 1457.3.2.4 Voids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1477.3.2.5 Vent Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1567.3.2.6 Air Entrapment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1567.3.2.7 Gels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1577.3.2.8 Poor Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

7.3.3 Functional Product Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1607.3.4 High Melt Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1607.3.5 High Motor Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1617.3.6 Wear Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

7.4 Systematic Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1637.5 Machine Troubleshooting and Maintenance . . . . . . . . . . . . . . . . . . . . . . . 164

7.5.1 Check the Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1657.5.2 Unusual Noises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1657.5.3 Drive Motors and Belts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1677.5.4 Spare Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1677.5.5 Screw and Barrel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1677.5.6 Extruder Maintenance Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . 168

7.6 Troubleshooting Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

8 New Developments in Extrusion and Methods to Increase Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

8.1 General Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1758.2 High-Speed Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

Contents  XI

8.2.1 Melt Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1758.2.2 Extruders without Gear Reducer . . . . . . . . . . . . . . . . . . . . . . . . . . 1768.2.3 Energy Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1778.2.4 Change-over Resin Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . 1778.2.5 Change-over Time and Residence Time . . . . . . . . . . . . . . . . . . . . . 177

8.3 Multi-Strand Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1788.4 Reducing Material Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

8.4.1 Low Cost Filler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1808.4.2 Recycled Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1828.4.3 Foamed Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1828.4.4 Pre-compounded Material vs. In-house Compounding . . . . . . . . 1838.4.5 Start-up, Change-over, and Shutdown . . . . . . . . . . . . . . . . . . . . . . 1838.4.6 Polymer Processing Aids (PPA) . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

8.5 Increased Automation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1868.6 Efficient Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

8.6.1 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1878.6.2 Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1878.6.3 Feed Stock Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1888.6.4 Flood Feeding versus Starve Feeding . . . . . . . . . . . . . . . . . . . . . . 1888.6.5 Purging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

8.6.5.1 Melt Displacement Behavior . . . . . . . . . . . . . . . . . . . . . . 1908.6.5.2 Effect of Viscosity Differences . . . . . . . . . . . . . . . . . . . . . 1938.6.5.3 Effect of Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1948.6.5.4 Dynamic versus Static Purging Methods . . . . . . . . . . . . 1958.6.5.5 Purging Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1988.6.5.6 Practical Rules to Reduce Purge Times . . . . . . . . . . . . . 198

8.6.6 Methods to Reduce Energy Consumption . . . . . . . . . . . . . . . . . . . 2008.6.6.1 Energy Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2008.6.6.2 Energy Cost per Kilogram . . . . . . . . . . . . . . . . . . . . . . . . 2008.6.6.3 Energy Cost per Year . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2008.6.6.4 Barrel Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2008.6.6.5 Heat Loss at the Extrusion Die . . . . . . . . . . . . . . . . . . . . 2018.6.6.6 Melt Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2018.6.6.7 Pre-Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2028.6.6.8 Use of Filled Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2028.6.6.9 Tips to Reduce Energy Use in Extrusion . . . . . . . . . . . . 202

8.6.7 Flexible Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2038.7 Statistical Process Control (SPC) and Design of Experiments (DOE) . . . 2068.8 Causes of Process Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

8.8.1 Melt Temperature Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2088.8.2 Melting Related Instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

8.9 Grooved Feed and Grooved Barrel Extruders . . . . . . . . . . . . . . . . . . . . . . . 2098.9.1 Adjustable Grooved Feed Extruder . . . . . . . . . . . . . . . . . . . . . . . . 2108.9.2 Grooved Barrel Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

8.10 The Rotary Channel Pump (RCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

XII  Contents

8.11 New Developments in Mixing and Screw Design . . . . . . . . . . . . . . . . . . . 2138.11.1 Elongational Mixing Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2138.11.2 Barrier Screws with Elongational Mixing Action . . . . . . . . . . . . . 2148.11.3 Floating Sleeve Intermeshing Pin Mixer . . . . . . . . . . . . . . . . . . . . 2158.11.4 High Heat Transfer (HHT) Screw Design Technology . . . . . . . . . 2168.11.5 The Single Screw Compounding Extruder (SSCE) . . . . . . . . . . . . 217

8.12 Fiber Reinforced Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2188.12.1 Conventional Methods to Make Fiber Reinforced Plastics . . . . . . 2188.12.2 Nexxus Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

8.13 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

9 Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2239.1 Appendix 1: Recommended list for further reading . . . . . . . . . . . . . . . . . 2239.2 Appendix 2: Extrusion Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

9.2.1 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2309.2.2 Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

1.3 Components of an Extruder  5

1.3Components of an Extruder

In this section we will discuss: the extruder screw the screen pack the extruder barrel the extrusion die the feed throat the extruder drive the feed hopper the reducer barrel heating and cooling gear pumps the breaker plate instrumentation and control

1.3.1The Extruder Screw

The heart of the extruder is the extruder screw. This is a long cylinder with a heli-cal flight wrapped around it, see Figure 1.6. The screw is very important because conveying, heating, melting, and mixing of the plastic are mostly determined by the screw. The stability of the process and the quality of the extruded product are very much dependent on the design of the screw. The screw rotates in a cylinder that fi ts closely around it.

Figure 1.6 A single flighted extruder screw

1.3.2The Extruder Barrel

The cylinder is called the extruder barrel. The barrel is a straight cylinder usually equipped with a bimetallic liner; this liner is a hard, integral layer with high wear resistance. In most cases, the wear resistance of the barrel should be better than that of the screw. The reason is that the screw is much easier to rebuild and replace than the barrel. Bimetallic barrels usually cannot be rebuilt.The barrel may have a vent opening through which volatiles can be removed from the plastic, see Figure 1.7, a process called devolatilization. An example is the re-moval of moisture from a hygroscopic plastic. An extruder with a vent port should use a special screw geometry to keep the plastic melt from coming out of the vent port; such a screw is called a “two-stage screw,” see Figure 1.7.

Functions

6  1 Extrusion Machinery

Figure 1.7 A vented extruder barrel with a two-stage screw

1.3.3The Feed Throat

The feed throat is connected to the barrel; it contains the feed opening through which the plastic material is introduced to the extruder. The feed throat usually has water-cooling capability because we have to be able to keep the feed throat tempera-ture low enough to keep the plastic particles from sticking to the wall. To improve the intake capability of the feed throat, the feed opening can be offset as shown in Figure 1.8 and have an elongated shape. The length of the feed opening should be about 1.5 times the diameter of the barrel and the width about 0.7 times the dia-meter.Some extruders do not have a separate feed throat, but the feed opening is ma-chined right into the extruder barrel. There are both advantages and disadvantages to such a setup. The advantages are lower cost, fewer parts, and no problems with alignment of the barrel to the feed throat. Disadvantages are that it is more difficult to create a thermal barrier between the hot barrel and the cold feed throat region and good cooling of the feed throat region is more difficult.

Tangentialdesign

1.5D

0.7D AA

D

Top view Section A-A

Figure 1.8 Preferred geometry for feed opening in the feed throat

Material intake

1.3 Components of an Extruder  7

1.3.4The Feed Hopper

The feed throat is connected to the feed hopper and the extruder barrel. The feed hopper holds the plastic pellets or powder and discharges the material into the feed throat. The hopper should be designed to allow a steady flow of material. Steady flow is best achieved with a circular hopper with a gradual transition in the conical section of the hopper, see Figure 1.9.

Figure 1.9 Good hopper design (left) and bad hopper design (right)

For difficult bulk materials, special devices can be used to promote steady flow through the hopper; such as vibrating pads, stirrers, wipers, and even crammer screws to force the material to the discharge, see Figure 1.10.

  Figure 1.10  Example of crammer feeder

1.3.5Barrel Heating and Cooling

The extruder barrel has both heating and cooling capability. Heating is usually done with electrical band heaters located along the length of the extruder. The heaters can be mica insulated heaters, ceramic heaters, or cast-in heaters. In cast-in heaters, the heating elements are cast in a semi-circular block of aluminum or bronze; these heaters provide good heat transfer. Aluminum cast heaters can heat up to 400 °C, while bronze cast heaters have a maximum operating temperature of  about 550 °C. Other types of heating can be used, such as induction heating,

Conveying material

Various heating methods

38  2 Instrumentation and Control

The threaded probe with the sapphire window can be used in combination with a simple IR thermometer. This allows IR melt temperature measurement in the ex-truder barrel or in the die.IR temperature measurement provides two important benefits. One, the response time is fast, about 10 milliseconds. Two, the measurement does not disturb the flow as is the case with an immersion probe. Because of the fast response, the IR mea-surement can detect rapid changes in melt temperature that cannot be detected by an immersion melt temperature probe. Melt temperature variation will be discussed next.

Melt Temperature Variation in ExtrusionThe melt temperatures in extrusion result from viscous dissipation and heat trans-fer. In drag flow, the shear rates and viscous dissipation are relatively uniform. However, the heat transfer to the screw and barrel results in large temperature dif-ferences within the polymer melt. The largest temperature gradients tend to occur at the barrel surface.The melt temperature distribution can be determined by performing a non-isother-mal analysis of the flow in the screw channel. In the case of a non-Newtonian poly-mer melt this is typically done using finite element analysis (FEA). Figure 2.24 shows a color contour plot of melt temperatures in the screw channel of a 63 mm single screw extruder running a 0.2 melt index high density polyethylene (HDPE) at 100 rpm. The vertical axis has been stretched about eight times to make it easier to examine the temperature distribution.

Figure 2.24 Melt temperature distribution in 63 mm extruder running at 100 rpm

The top surface is the barrel, the bottom surface is the root of the screw, the left vertical boundary is the pushing flank of the flight, and the right vertical boundary

IR temperature measurement provides two important benefits:

1) fast response, 2) no disturbance of flow

Melt temperature distribution can be

determined by perform-ing a non-isothermal

analysis of the flow in the screw channel

Melt temperatures in the screw channel are

highly non-uniform

2.4 Collection and Interpretation of Extrusion Process Data  39

is the trailing flank of the flight. It is clear that the melt temperatures are highly non-uniform. The temperatures close to the barrel are relatively low because of the heat transfer to the barrel – the barrel cools down the melt that is in close proxim-ity to the barrel. The temperatures at the pushing flight flank are low because the cool melt close to the barrel moves down along the flight when it reaches the push-ing flight flank.At the root of the screw, the cool melt from the pushing flight flank moves toward the trailing side of the flight. If there is no heat transfer with the screw, the melt temperatures will gradually increase as the melt moves from the pushing flank to the trailing flank. The melt reaching the trailing flight flank moves up along the flight until it gets close to the barrel. At that point the cycle starts again. The outer region of the screw channel stays relatively cool because of the heat transfer from the melt to the barrel. The situation is quite different for the inner region of the screw channel.The melt in the inner region remains in this region as it travels down the length of the screw channel – it will not come into close proximity of the barrel. The inner region is thermally insulated from the barrel by a relatively thick layer of polymer melt. As a result, the temperatures in this region increase higher than in any other part of the channel – it is a natural hot spot. In Figure 2.24 the temperatures in the hot spot are more than 100 °C above the barrel temperature.When the screw discharges the melt, this melt will be non-uniform in temperature. A number of studies have analyzed the variation of melt temperatures in extruders. One such study was made by E. Brown and A. Kelly at Bradford University in Eng-land. In this work, a fast response thermocouple (TC) mesh was used to measure melt temperature variation using three different extruder screws. The TC mesh was located in the breaker plate recess of the extruder barrel, see Figure 2.25.

Figure 2.25 Experimental setup for melt temperature study

Melt temperature was measured at multiple locations, see Figure 2.26. It is clear from this figure that the melt temperatures across the channel are quite non-uni-form with a low temperature of 190 °C and a high temperature over 215 °C.

Hot spots tend to form in the center region of the screw channel

40  2 Instrumentation and Control

Figure 2.26 Melt temperatures versus radial distance from the center

The melt temperatures vary not only across the melt stream but also over time – this is shown in Figure 2.27.

Figure 2.27 Melt temperature versus time

The melt at TC4 (radial location –10 mm in Figure 2.26) drops from 215 °C to 180 °C within four seconds and then increases again to almost 215 °C within two seconds. This is rapid and substantial melt temperature variation! Interestingly, this melt temperature variation cannot be detected with an immersion melt tem-perature probe because of the slow response time.In this study, the melt temperatures were also measured with an infrared thermo-meter. The results are shown in Figure 2.28.

5.3 Melt Conveying  89

Figure 5.14 Cross section of a barrier screw

One variable that affects the melting in an extruder is the temperature at which the plastic is introduced to the extruder. By preheating the plastic in the feed hopper or before, the amount of heat that has to be added to melt the plastic in the extruder is reduced and, as a result, melting occurs earlier in the extruder. When it is sus-pected that an extrusion problem is related to melting, preheating is a method of diagnosing the problem.The barrier screw has the following advantages:

The barrier screw achieves more stable extrusion than a simple conveying screw.

With a barrier screw, there is virtually no chance of unmelted material beyond the barrier section.

There is a certain amount of dispersive mixing that occurs as the plastic melt flows over the barrier flight into the melt channel.

Next to these advantages, there are the following disadvantages: Barrier screws are no better in performance than non-barrier screws designed

with effective mixing sections. Barrier screws tend to be more expensive than non-barrier screws, particularly

when purchased from an original equipment manufacturer (OEM). Because the solid material is restricted to the solids channel, the barrier screw

is inherently more susceptible to plugging. This occurs when melting cannot keep up with the reduction in the size of the channel in the compression section of the screw, resulting in the solid material getting stuck in the screw channel. This creates a momentary obstruction to flow and leads to surging. Surging is a variation in extruder output.

5.3Melt Conveying

Melt conveying starts when the melting is completed in the extruder. Strictly speak-ing, melt conveying starts when melting starts, because the melting zone is where we have both solids conveying and melt conveying with the amount of solid mate-rial gradually decreasing and, at the same time, the amount of melted material

Pre-heating material

Barrier screw advantages

Disadvantages

Mechanisms of conveying

90  5 How an Extruder Works

gradually increasing. However, we define the melt-conveying zone as the region where all the plastic is completely melted.The mechanism of melt conveying is viscous drag. In other words, the viscous forces acting on the plastic melt are responsible for the forward conveying of the melt. As we saw in the solids conveying zone, the viscous force at the barrel is re-sponsible for forward conveying, while the viscous force at the screw is a retarding force. As a result, melt conveying is improved by reducing the barrel temperature and increasing the screw temperature. Interestingly, screw heating in the melt con-veying zone makes more sense than barrel heating.The optimum screw geometry for melt conveying can be determined from extrusion theory. The optimum helix angle is dependent only on the degree of non-Newtonian behavior of the plastic melt; it can be determined from the following expression:

optimum helix angle degrees (power law index = +13 5 16 5. . )) (5.1)

The optimum helix angle for melt conveying decreases as the power law index de-creases or the plastic is more shear thinning. A similar expression can be derived for the optimum depth of the channel in the melt-conveying zone. The optimum depth depends on the viscosity, the pressure gradient, and the power law index. When the plastic becomes more shear thinning, the channel depth should be re-duced to maintain good melt conveying.

5.3.1Melt Temperatures

Because of the low thermal conductivity of the plastic melts, the temperatures in the melt-conveying zone can vary substantially. Local temperatures are difficult to measure because it is hard to put a probe in the screw channel while the screw is rotating. Melt temperatures can be predicted from extrusion theory using numeri-cal techniques. A popular technique for this purpose is finite element analysis (FEA). With this technique the flow patterns and temperature distribution can be predicted.Figure 5.15 depicts the temperature distribution in the screw channel by looking at a cross section of the screw channel. The temperatures are shown in colors; differ-ent colors represent different temperatures, just like the weather map on the back page of USA Today. The lower surface of the picture is the root of the screw; the upper surface is the extruder barrel. The barrel is maintained at 175 °C and the screw surface is considered insulated (adiabatic). It can be seen in the figure that the highest melt temperatures occur in the mid-region of the channel, while the outside region of the channel remains at a lower temperature.

Optimum screw geometry

Optimum helix angle

Predicting melt temperature by FEA

Distribution of melt temperature

5.3 Melt Conveying  91

Figure 5.15 Predicted melt temperatures in the screw channel

The reason for this temperature distribution is the way the plastic melt flows along the screw channel. We can illustrate this flow by unrolling the screw channel and by looking at it as a straight trough (see Figure 5.16) and the barrel as a flat plate.

Figure 5.16 Flow along the unrolled screw channel

If we look at the flow relative to the screw, then the barrel moves in tangential direction, vb, making an angle φ with the channel. Angle φ is the helix angle of the screw flight. A fluid element close to the barrel surface flows in the direction of the barrel until it gets to the pushing side of the flight. At this point, the element moves downward and then crosses the screw channel. When the element gets to the trailing side of the flight, the element moves up again close to the barrel surface and the element starts moving in the direction of the barrel again. This pattern re-peats itself numerous times as long as the regular flight geometry is maintained.If we look at the flow in the cross section of the screw channel (see Figure 5.17), we see the material moves to the pushing side of the flight at the top of the channel. This flow results from drag flow. At the bottom of the channel, the material moves toward the trailing side of the flight. This is a pressure flow resulting from the fact that the pressure at the pushing side of the flight is higher than at the trailing side

Movement of fluid ele-ment through the barrel

Different types of flow through channel

92  5 How an Extruder Works

of the flight. If the leakage flow through the flight clearance is negligible, the amount of material flowing to the pushing flight flank is the same as the amount of material flowing to the trailing flight flank. Thus, we get a recirculating flow1 as shown in Figure 5.17.

Figure 5.17 Recirculating flow in the cross section of the screw channel

The fluid is sheared as it flows along the screw channel and, as a result, there is viscous heat generation in the plastic melt. The actual temperatures that occur at different points in the screw channel are determined not only by viscous heating, but also by how efficiently this heat can be removed. If the barrel is cooled, the melt flowing close to the barrel surface can exchange heat and cool down efficiently. When this outer layer moves along the screw surface, it remains relatively cool even if the screw is insulated.However, the situation is quite different for the inner layer. Because this layer is trapped in the inner recirculating region, it never gets close to the barrel. As a re-sult, this layer has very limited opportunity for removal of its heat; the outer layer of plastic melt essentially insulates the inner layer. This explains why the tempera-ture in the inner region of the screw channel tends to be higher than in the outer region. In Figure 5.15, the temperature in the center region is about 60 °C higher than the barrel temperature. Thus, it is clear that considerable melt temperature differences can occur in the screw channel.If these temperature differences are carried to the end of the screw, the melt dis-charged into the die is not thermally homogeneous. This leads to flow problems in the die and distortion of the extruded product. It is important, therefore, to try to keep these non-uniform melt temperatures from reaching the end of the screw.The most efficient method to do this is by incorporating mixing elements into the design of the screw. Mixing sections are not only important when we mix different plastics, but also when we extrude a single plastic in order to achieve a thermally homogeneous melt at the end of the screw.

1 There are also small velocity components in the normal direction close to the flight flanks. At the pushing flight flank, the normal flow is downward toward the root of the screw; at the trailing flight flank, the normal flow is upward, toward the barrel. The normal flow also results from pressure differences. For instance, the pressure at the top of the pushing flight flank is higher than at the bottom of the flight flank, which is why the flow is downward in this region.

Melt temperature close to surface

Melt temperature of inner layer

Importance of homoge-neous melt temperature

5.4 Mixing  93

5.4Mixing

Mixing takes place both in the melting zone as well as in the melt-conveying zone of the extruder. The solid plastic typically moves in plug flow, which means that there is no relative motion between the solid plastic particles. As a result, there is little or no mixing in solids conveying. This means that complete mixing does not start until all the plastic has melted. For this reason, we will look at mixing only in the melt conveying zone of the extruder.

5.4.1Distributive Mixing

The extent of distributive mixing can be determined from the total shear deforma-tion of the plastic melt in the melt conveying zone. The total shear deformation is also called the total shear strain; it is determined by the product of the shear rate and the length of time that the fluid is exposed to the shear rate. For instance, if the plastic melt is exposed to a shear rate of 100 s–1 for 15 seconds, the resulting shear strain is 100 × 15 = 1500. The shear strain is dimensionless. The shear rate is de-termined by the velocity profiles in the extruder.Mixing in single screw extruders is determined mostly by the two main velocity components in the screw channel. These are the velocity in the direction of the channel (z-direction) and the velocity in the cross-channel direction (x-direction), see Figure 5.18.

  Figure 5.18  The two main flow components in a single screw extruder

There is also a velocity component in the third direction (y-direction) parallel to the flight flank. This velocity component is usually very small and therefore can usu-ally be neglected. The velocities in the down-channel direction depend on the pres-sure gradient; this can be positive, zero, or negative. When the pressure gradient is positive, pressure is increasing along the melt conveying zone; when the pressure gradient is negative, pressure is decreasing along the melt conveying zone. Down-channel velocity profiles for different values of the pressure gradient are shown in Figure 5.19.

Mixing in the melt stage

Definition

Pressure gradient

94  5 How an Extruder Works

Figure 5.19 Down-channel velocity profiles for three pressure conditions

The cross-channel flow is shown in Figure 5.17. At the top of the channel, the mate-rial flows to the left by drag flow and at the bottom of the channel, the material flows to the right by pressure flow. Figure 5.20 shows the cross-channel velocities.

vbx

  Figure 5.20  Cross-channel velocity profile

The shear rate can be determined from the velocity profile; the shear rate is equal to the slope of the velocity profile. This slope of the velocity profile is also called the  velocity gradient. From the down-channel velocities, we can determine the down-channel shear rates; these are shown in Figure 5.21.

Figure 5.21 Down-channel shear rates for three pressure conditions

When the pressure gradient is positive, the shear rates increase toward the barrel surface; when the pressure gradient is zero, the shear rate is constant, and when the pressure gradient is negative, the shear rates decrease toward the barrel sur-face. The same approach can be used to determine the cross-channel shear rate from the cross-channel velocities. The cross-channel shear rate profile is shown in Figure 5.22.

Types of flow

Shear rate

6.8 Inspection and Training  133

6.8Inspection and Training

It is the responsibility of the employer to establish and follow a program of periodic inspections of the extruder to ensure that all safeguards are in proper operating condition. The employer must also train operators in safe extruder operation before actually working on one. An effective training program should include the follow-ing four steps:

Tell workers how to do it safely Show them the safe way to do it Encourage them to ask questions Have them show you that they know how to do it safely

Three important rules regarding safety training: Never assume that employees know how to carry out a new task Frequent reminders should be given concerning safety procedures Never assume that safety rules are remembered

It is good practice to have regular safety inspections, at least once a quarter. The objective is to identify as many safety and health hazards as possible before they can cause an accident. The following checklist can be used for a successful safety inspection.

Housekeeping□ Is the work place clean and orderly?□ Are floors free from protruding nails, holes, and loose boards?□ Are the aisles and passageways kept clear of obstructions?□ Are permanent aisles and passageways clearly marked?□ Are covers or guardrails in place around open pits, tanks, and ditches?

Floor and wall openings □ Are ladder ways and door openings guarded by a railing?□ Do skylights have screens or fixed railings?□ Do temporary floor openings have standard railings or guards?□ Are wall openings with a drop of more than 1.2 meter (4 feet) guarded by a railing?□ Do all stairways with four or more risers have a handrail?□ Are stairways strong enough, adequately illuminated, and slip resistant?

Escape routes□ Are there enough exits to allow prompt escape?□ Do employees have easy access to exits?□ Are exits unlocked to allow people to leave?□ Are exits and exit routes equipped with emergency lighting?

Proper training

Checklists

Housekeeping

Floor and wall openings

Escape routes

134  6 How to Run an Extruder

Personal protective equipment□ Is the required equipment provided, maintained, and used?□ Does the equipment meet requirements and is it reliable?

Employee facilities□ Are facilities kept clean and sanitary?□ Are toilets kept clean and in good repair?□ Are cafeteria facilities a sufficient distance from toxic materials?

Medical and first aid□ Is there a hospital, clinic, or infirmary nearby?□ Are employees trained in first aid on each shift?□ Are physician-approved first aid supplies available?□ Are first aid supplies replenished as they are used?

Fire protection□ Are fire extinguishers available for the types of fire most likely to occur?□ Are there enough fire extinguishers available to do the job?□ Are fire extinguisher locations clearly marked?□ Are fire extinguishers properly mounted and easily accessible?□ Are all fire extinguishers fully charged and operable?□ Are special purpose extinguishers clearly marked?

Material handling and storage□ Is adequate clearance allowed in aisles?□ Are stacked materials interlocked, locked, and limited in height to maintain

stability?□ Are storage areas kept free of tripping, fire, explosion, and pest hazards?□ Is proper drainage provided?□ Are signs warning of clearance limits posted?□ Are powered industrial truck operators adequately trained?

Machine guarding and signs □ Are point-of-operation guards in place and working on all equipment?□ Are all belts and pulleys less than 2.1 meters (7 feet) from the floor guarded?□ Are spinning parts guarded?□ Are warning signs properly located? Show warning signs on the extruder, see

Figure 6.10.

Personal protective equipment

Employee facilities

Medical and first aid

Fire protection

Material handling and storage

Machine guarding and signs

Symbols

3D finite element analysis  19934CrAlNi7  185

A

abnormal sounds  165abrasive  162abrasive compounds  167abrasive fillers  18abrasive fillers downstream  173abrasive wear  162, 173ABS  105, 130accelerometer  166acceptable variation  206accidents  132accumulation in the hopper  188acetal (POM)  65, 130, 132AC motors  14, 167acrylic (PMMA)  64, 105acrylonitrile butadiene styrene

(ABS)  64active flight flank  85actual operation  123, 128actual temperatures  92adhesion  56adhesive  58adjustable calibrating basket 

204adjustable calibration sleeve 

204adjustable depth  24adjustable die gap  203adjustable die restriction  156

adjustable flow restriction  179adjustable grooved depth  210adjustable grooved feed extruder

(AGFE)  210adjustable melt temperature

probe  36adjustment nuts  57adjustment of the concentricity 

115Advantage  204AGFE  210agglomeration  60, 189agricultural research  207air cooling  8air currents  20, 144, 189air entrapment  147, 156air filters  167air flow  168air hose  129air knife  55air velocity  25aisles  133allowed moisture content 

108aluminum alloys  185aluminum cast heaters  7ambient air  201ambient temperature  20, 144,

187amorphous  64, 160amorphous plastics  64, 70, 72,

76, 112, 124, 172, 200amount of cooling  187

amount of resident polymer at the discharge  192

amperage of barrel heaters  168amplitude of the oscillations  27analysis of process problems  71annular channel  219annular dies  12, 114anti-oxidant  185anti-seize compound  167appearance  201appearance problems  73, 139,

144, 174arc-over  167armature cooling blower intake 

169aromatic  185artificial intelligence-based

technology  28attrition of the fiber  218automatic die adjustment  116automatic feed to hopper  171automatic hopper feeder  144automatic screen changers  11,

203automatic shutoff  21, 132automation  175, 186auto-tuning controller  28axial adjustment  115axial length of the feed opening 

143axial loads  16axial melting length  87, 227Axon mixing section  100

Index

234  Index

B

B-10 life  17backlash  143backlash of the gearbox  16back relieving  112ball mill  104barium chromate  194barrel  5, 87, 124, 167, 169barrel and die temperatures  187barrel cooling  200, 201barrel friction  84barrel liner  167barrel or die temperature

variations  171barrel pins  215barrel pressure  140barrel temperature  19, 87, 128,

140, 156, 171barrel temperature

measurement  24barrel temperature sensors  167barrier flight  88, 105, 214barrier screw  88, 144, 214batch internal mixers  59Battenfeld  175beard formation  85bearing covers  165bearing problems  165bearing temperature  166Beddus  203belt  134, 167, 169belt guards  168belt tension  167beneficiated calcium carbonate 

182bimetallic liner  5biological degradation  146black box process  137black specks  145bleed trim  203bleed valve  11blenders  157blending  171blister ring  102, 160blockage  161

blockage along the screw  140, 172

blocking  140blower motors  170blowers  8blow molding  142, 209blown film  114, 209blown film dies  12blown film extrusion  142, 181blown film line  59blow up ratio  59bore-scope  167boron nitride  85, 198brass  130breaker plate  9, 31, 129, 140breaker plate recess  130, 170bridge with multiple probes  24bridging  79, 140, 171, 189broader process control  189bronze metal particles  165brush holder  169brushless DC drives  15brushless DC motors  167brush sparking  167BSP feeders  213bubbles  156, 174bucket brigade  18buildup of colorant  195buildup of material inside the die 

145buildup of metal particles  161bulk density  78, 138, 140, 213bulk handling equipment  157bulk handling hardware  157bulk materials  78bulk solids pump (BSP)  213burning  73bushing  167, 169butt end of the screw  167Byk-Gardner  195

C

cable jacketing  115CaCO3  180cafeteria facilities  134

calcium carbonate (CaCO3)  47, 180, 182

calcium deposits  187calcium scale  47calibrating  61, 138calibrating device  53calibration  204calibration of all temperature

controllers  170calibrator  53, 145, 204cancer causing  183candles  130capability of measuring

instruments  138capillary  21capillary strain gage  22capillary strain gage transducers 

132carbon black  194Cartesian coordinate system 

225cartridge heater  85cast acrylic  130cast film extrusion  142cast-in heaters  7cast iron powder  165catalytic properties  185catalytic surface conversion  85catastrophic failure  165causes of process variation  52,

208cavity mixers  98cavity transfer mixer (CTM)  98center region  97centrifugal action  60centrifugal dryer  60ceramic heaters  7chance of degradation  97, 104,

126, 216change-over  177, 183, 195, 203change-over time  177, 190, 194,

203changes in ambient conditions 

144chart recorder  128chemical degradation  146

Index  235

chemical purging compounds  130

chemical reactions  86chilled air  202chill roll casting  55chill roll unit  55chillWARE  149chips  169chloride ion concentration  170chlorinated polyethylene  105chlorophyll  194choker bar  57, 156chromium pigments  194circular dies  12circular feed hopper  79circular hopper  7, 79circumferential grooves  98circumferential orientation  117clamp area  169clam shelling  118, 119clean filter screen  170cleaning tools  130clean screw  172clean the die  129clean the extruder  123clearance  134, 161clear plastics  194clinic  134closed-loop control of extruded

tubing  128closed-loop control systems  54CO2  216coated wires  115coat hanger  119coat hanger manifold  119coating  56, 85coefficient of friction  140coextruders  202coextrusion  56coextrusion die  14coextrusion flow  193coiler  61cold air  206cold drawing of man-made fibers 

113cold start-up  125

collapsing frame  59color  138, 194colorants  194color contour plot  38colored plastics  194colored resin particles  194colored resins  198colorimeter  194color measurement  195color veil  195commodity polymers  191commutator  169compacted clump  79comparative facts  163compatibilizer  145, 174competitive disadvantage  180competitive world market  219complete extrusion line  200composition of the metal

surface  185compounding extruder  183compounding lines  59compounding procedure  145,

174compressibility  78, 79compression ratio  157, 162, 173compression ratio of the screw 

144concave side  113concentricity  116concentricity adjustment  116concentric twin screw extruder 

211condition of seal  169conductive melting  227conductor  115cone-and-plate rheometer  74conical nozzle  206conical screws  3consistency index  70consistency of the feed material 

188contact pressure  204contaminants  9contamination  123, 145, 147, 157,

165, 167, 173

contamination of the plastic  160

contiguous solids melting (CSM)  34, 85, 227

continuity  170continuous band of screen

material  12continuous improvement  186continuous internal mixers  59continuous screen changers  11control  19, 20control charts  207conventional barrier  214conventional extruders  176conventional SPC  207conventional (vulcanizable)

elastomers  66conveying ability of the pump

section  109conveying capability  87conveying capacity  156conveying characteristics  141,

210conveying rate of the second

stage  110conveying system  173cooling  7, 9, 13, 61, 72, 111, 112,

156, 185cooling capacity  216cooling channels  187cooling device  53cooling rate  20, 128cooling section  55cooling system  160, 172cooling to the feed throat  124cooling water temperature  20copper mesh cloth  130copper phthalocyanine  194coring the screw  85corona discharge treatment  56corona treaters  132co-rotating twin screw extruder 

2corrosion pencil anodes  169corrosion-resistant materials 

162, 173

236  Index

corrosive attack  123corrosive substance  173corrosive wear  162, 173cost effective extrusion  198counter-pressure of the haul-off

tracks  204counter-rotating twin screw

extruder  3coupling  15cracked bearing or broken gear 

165cracking  160, 167cracks  169crammer feeder  7, 78, 79, 171crammer screws  7CRD  217CRD barrier section  214CRD mixer  105, 213critical diehead pressure for vent

flow  110critical draw ratio  142critical level in the hopper  144critical process variables  187critical skin thickness  148critical solid skin thickness  149critical value  142cross-channel flow  94cross-channel shear rate  94cross-channel shear strain  96cross-channel velocities  94crosshead  115crosshead die  115crosslinked material  157crosslinking  64crosslinking reaction  64cross section of the screw

channel  91crystal  64crystalline regions  64crystalline wax  130crystallites  64crystal polystyrene  65CSM  34, 228cubic  60curing  66

cut off flow from the hopper  129

cutter  53, 61cutter knives  60cycle time  141cyclical noise  165cyclic variation  49, 141

D

damaged belts  167dark colors  123, 194, 198Darnell and Mol  225DA software  187data acquisition (DA)  187data acquisition system (DAS) 

21, 29, 50, 128, 143data collection rate  29, 44DC brush motor  14, 167DC motor  14dead spots  23, 98, 119, 157decomposition  125deep flighted screw  160defect  163defective bearings or gear teeth 

165degassing  73, 77, 86, 108degradation  18, 73, 145, 147,

201, 214 – problems  138 – promoting substances  147

degradation of the plastic  109degree of fill in the grooved

barrel section  210degrees of shear thinning  191demixing action  96densify feed stock  171density  71, 74, 180, 182depolymerization  130depth filtration medium  157Derenzinski  225derivative action  28descaler  47design of experiments (DOE) 

206, 207devolatilization  5, 77, 108

dial indicator  166diameter of the calibration

basket  204diameter recognition system 

204diamondback hopper  80diaphragm  21, 31, 132dicer  60die  1, 13, 140, 156, 167die design  13, 111, 145, 172die drool  85, 145, 174die face pelletizers  60die forming  110die gap  156diehead pressure  16, 20, 110diehead pressure fluctuation 

128die heaters  167die inlet pressure  30die land  174die lines  174die lip buildup  183die opening  174die plate freeze-off  60die restriction  161die swell  111die temperature  19, 124, 156, 174die temperature sensors  170die tooling  124different functional zones  225digital DC brush drives  15dimensional changes  50dimensional control  208, 214dimensional variation  208dimensionless layer thickness 

190dimensionless time  190dimensions of the extrudate 

128dimensions of the extruded

product  20, 127direct drive  15direct extrusion  183, 217dirty oil  165discharge channel  219discharge end of the screw  140

Index  237

discharge melt temperature  201discharge pressure  49discoloration  125, 145discolored armature  167Disco purge  195diskpack  213dislodge the bridging  171dispersed solids melting (DSM) 

86, 227disperse mixing ability  214dispersive  214dispersive mixing  107, 213, 214dispersive mixing capability  158dispersive mixing elements  157dispersive mixing sections  102displacement behavior  193displacing polymer  193distortion of the extruded

product  92distributive  213distributive mixing  93, 214distributive mixing devices  208distributive mixing element  158distributive mixing sections  98ditches  133diverging discharge channel  219door interlock  170door openings  133double flighted screw  88, 173double wave screw  101down-channel shear rates  94down-channel shear strain  96down-channel velocity profiles 

93downstack mode  55downstream cooling conditions 

128downstream equipment  124downstream feed port  60downtime  165, 183, 190downtime needs  186drag flow  94, 229drag flow rate  140drag induced conveying  78, 80drag induced melt removal  87,

227

drainage  134drawdown  13, 111draw ratio  142, 174draw resonance  141, 142, 174drive  169 – potentiometer  170

drive belts  165, 167drive fuses  167drive motors  167drum or disk extruder  2dry die face pelletizers  60dryer  200drying capacity  123drying plastics  108drying system  53DSM  228DSM melting mechanism  227DSM model  227dual heads  203dual strand extrusion  178Dulmage  100Duranickel  162dust  167Dutch twill  10dyes  194Dynamar from Dyneon  183dynamic choke  109dynamic purging methods  195,

197dynamic response  22

E

Easychange  203eccentrically  167edge trim  203effective length  82effective length of the screw 

188effective mixing action  100effectiveness of purging  198effect of air currents  25efficiency  175efficient cooling  181efficient distributive mixing  215efficient extrusion  186, 187

efficient extrusion operations  201

efficient melting  87efficient operation  187efficient troubleshooting  187Egan mixer  104Egan mixing section  103E-gels  157Egeplast Werner Strumann

GmbH  203elastic effects  179elastic nature  111elastomers  66electrical band heaters  7electrical codes  132electrical enclosures  132electrical properties  160electric drill  130electricity  131electric motor  14elongated feed opening  80elongational  214elongational flow  106, 213elongational mixing  214elongational mixing action  214elongational mixing devices  213elongational stresses  102emergency lighting  133emergency stop  132, 135emergency stop switch  169employee facilities  134energy consumption  100, 177,

181, 200, 202energy cost  200energy cost per kilogram  200energy cost per year  200energy efficiency  15, 16, 29energy loss  15energy reduction  183energy requirement in extrusion 

200energy savings  201energy use  203energy use of the extruder 

202engineering  138

238  Index

engineering calculations  13entanglements of the molecules 

70enthalpy  29, 72enthalpy difference  72entrapped air  11, 156environment  189epoxy  64, 105equilibrium moisture content 

108equipment  187equipment design  187Esde  175ethyleneacrylic acid (EAA)  74excessive die restriction  172excessively high pressures  125excessive noise  167excessive pressure  132excessive screen pack

restriction  172excess wear  169exit routes  133exits  133exit velocity  110extension cords  135external coefficient of friction 

78, 79external cooling  206extinguishers  134extraction section  110extraction section of the screw 

109extrudate swell  111extruded product  85extruder  1extruder barrel  5extruder barrel temperatures 

128extruder drive  14extruder feed hopper  206extruder motor load  184extruder output  169extruder output rate  204extruder performance  84, 187extruder screw  5, 124, 156

extruders without gear reducer  176

extrusion blow molding  181extrusion blow molding ma-

chines  53extrusion coating  57, 181extrusion compounding  59extrusion compounding lines 

53extrusion die  12, 110, 201extrusion equipment  186extrusion lamination  58extrusion line  53extrusion pressure  184extrusion technology  219extrusion theory  225

F

fabric  57Farrel  213fast cooling  147Fast Fourier Transform  44fast variation  141faulty bearings  166Fe2O3  194feed block system  14, 56feeders  157feed hopper  7, 78feed hopper design  171feed housing  187 – temperature  46

feed housing water flow rate  187

feeding characteristics  83feeding device  188feeding problems  126, 143, 171feed opening  6, 125, 143feed problems  124, 129feed section  77, 157, 167feed section casting  169feed stock characteristics  209feed stock variability  188feed stock variation  171feed temperatures  171feed throat  6, 78, 140

feed throat housing  84feed throat temperature  156feed tubes  157FFT  44fiber  12fiber addition  218fiber addition port  218fiber breakage  218fiber feed rate  219fiber reinforced plastics (FRP) 

218fiber spinning  142, 178fiber spinning lines  53fiber wetting  218fibrous strand bundles  219fibrous strands  219filled polyolefins  181filler  180film and sheet extrusion lines 

53film extrusion  183film lines  55filter  169final extruded product  183fines  157finite element analysis (FEA) 

90, 208first aid  134first aid supplies  134first stage  156first stage of the screw  109fishbone chart  147flame treatment  56flat film  12, 117flat film or sheet die  110flat plate  229flat plate approximation  229flat trough  229FLC  28flexible bands construction  204flexible manufacturing  203flexible membrane  57flex lip adjustment bolts  57flight clearance  87, 92flight flank radius  84flight helix angle  225

Index  239

floating sleeve intermeshing pin mixer  215

flood fed  126flood feeding  188, 210flood feeding rate  127flood feed rate  82floor openings  133flow along the unrolled screw

channel  91flow behavior of plastic melts 

67flow-chart  163flow of the feed material  188flow of tower/municipal water

source  168flow properties  111, 138flow rate  111flow rate of cooling water  187flow rate ratio (FRR)  192flow simulation  199flow splitter  115flow splitting  101, 179fluid heating  8fluidized bed  129fluorinated polymers  183fluorinated PPA  183fluoro-elastomer  142, 145fluoropolymers  123flushing action  190flushing out the resin  189flush lines with scale removing

compound  169flush-mounted melt temperature 

160flush-mounted probe  24, 172fluted mixing sections  102foamed plastics  182foam extrusion  182, 210, 216foaming action  130foil  57force balance  225forced conveying  18fork lift truck  132forming  77forward pumping capability  98,

100, 104, 214

four-motor CMG torque drive  175

fractional melt plastic  68fraying  167free extrusion process  53freeze-off  60frictional force  81, 225FRP compounds  218full factorials  207full intermeshing action  216fully beneficiated  182fully intermeshing  3fully streamlined die  119fumes  135functional product problems 

160functional product properties 

139functional zone  77fuzzy logic control  28fuzzy rules  28

G

gaskets  167gas-laden melt  216gearbox  15, 167, 169gearbox assembly  167gearbox problems  143gearcase  166gear or bearing problems  165gear pump  17, 48, 54, 60, 156,

161, 179gear reducer  16, 176gears  165gel  157, 173, 214, 215gel capture capability  173generation of a knowledge base 

28geometrical sections  77GFE  209glass fiber  162glass transition temperature  71,

76, 138, 160glued  166gouges  157, 169

granulators  202, 203gravity induced  80gravity induced conveying  78Gregory  103grooved barrel extruders  210grooved barrel in feed section 

171grooved feed extruders (GFE) 

83, 84, 157, 209, 210grooved feed section  78, 83grooved feed throat  141grooved liner  84grooves  157Gross  194ground connections  170grounds  132guardrails  133guards  133, 169, 170

H

hairnets  131hand-squeeze test  79hanger die  118hang-up  104, 173hang up or build up  85Hansen  181“hard” water  47Hastelloy  162haul-off  61, 204HDPE  74, 75, 141, 181head  204head/die cords  170head pressure  126health hazards  133heat  131heat-activated chemical reaction 

130heater clamping bolts  170heater contacts  132heater terminal connections 

170heat exchange  165heating  7, 72heat insulating blanket  201heat insulating material  201

240  Index

heat loss  201heat resistant gloves  129, 131heat resistant layer of plastic 

126heat-sensitive materials  105heat soak  124heat-soak cycle  130heat transfer  181, 187, 216heat transfer conditions  189heat transfer fluid  85Helibar extruder  211helical channels  116helical flight  5helical flow path  95helical orientation  103helical solid ribbon  35helix angle  84, 87, 91, 104helix angle of the barrier flight 

104hemi-spherical cavities  98herringbone gear  16HHT  217HHT screw geometry  216high die restriction  172high discharge pressures  217higher barrel temperature  87high filler levels  217high frequency envelope (HFE) 

166high frequency impact sounds 

166high friction  209high heat transfer (HHT) screw 

216highly compressible materials 

79highly corrosion-resistant 

162highly stabilized version of the

plastic  126, 157high melt index  123high melt index masterbatch 

159high melt temperature  139, 157,

160, 172

high molecular weight droplets  157

high motor load  139, 161high oil temperatures  165high precision extruded product 

15high-precision extrusion  18high precision operations  14high pressure  131high-pressure alarm  132, 135high pressure drop  104high restriction at screen pack 

172high-restriction die  110high-speed extruder  3, 177high-speed extrusion  175high-speed Helibar extruder 

211high-speed single screw extruder

(HS-SSE)  175, 183high-speed twin screw extruders 

82high stock temperatures  147high stress region  102, 106high temperature  161, 167high temperature and pressure

alarms  165high temperature plastics  123high viscosity plastics  160, 176,

193high voltage devices  132historical data  137hoist  129, 132hoop strength  117hopper  140, 157hopper barrier guards  169hopper loaders  203hopper slide valve  126hopper with a square or rectan-

gular cross section  79horseshoe die  118horseshoe manifold  119hoses  167hospital  134hot air  206hot plastic  131

hot spot  39, 208housekeeping  133hydraulic ram  11hydraulic screen changers  11hydrolysis  109, 202hygroscopic materials  5, 108hyperactive screw  201

I

identify the problem  163identify the process  163ID waviness  43IKV (Institut für Kunststoff-

verarbeitung = Institute for Polymer Processing)  182

imbalance  166imbalance between the first and

second stages of the extruder  156

immersion melt temperature probe  35

immersion probe  24, 172immersion TC  23immersion temperature probe 

160impending failure  165important process parameters 

19improper use of the plastic

product  160impurities  182IMS  198inadequate exhaust air flow 

167incoming material  157incompatible component  174Inconel  162in control  206incorrect screw design  110indigestion  210indigo  194indirect drive  16induction heating  7induction time  71, 73, 138inefficient venting  147

Index  241

infiltration  219infirmary  134infrared (IR) detectors  23infrared (IR) temperature

measurement  143infrared radiation  36infrared thermometers  36in-house compounding  183injection molding machines 

227inlet channel  12, 117inline  115inline die  115inner layer  92inner recirculating region  92,

96inner region of the channel  96inner vortex  206Inoex  204inorganic  194inorganic pigments  194input  165inside diameter of barrel  169inspection  133Institut für Kunststofftechnik

(IKT)  211instrumentation  19, 137, 187instrument panel  189insufficient barrel friction  172insulate all hot oil lines  202insulated TC  25insulated wires  132insulate extruder  171insulation spark testers  132insulation tape in conduit box 

169intake capability  6integrated sheet and thermo-

forming lines  53intelligent manufacturing

methods  175intensely cooled grooved feed

extruders  210interface  193, 226interface distortion  57interlocked  132

interlocking guards  135intermediate  165intermediate material  190intermediate pelletizing  183intermeshing action  48intermeshing region  216internal air pressure  54internal coefficient of friction 

78, 79internal cooling  206internal die surfaces  174internal heat generation  8internal screw heating  85internal stresses  113intractable plastics  4iron oxide  194irregular feeding  144IR temperature measurement 

38

J

J-Tex  85junction boxes  135

K

K&A Knoedler  175keyways  130Kramer  203Krause  197Krauss-Maffei  203K-tron  213Kuhne  175Kulikov  183Kynar from Atofina  183

L

labor intensive  204Labtech Engineering  217ladder ways  133laminating  56lamination  56land length  145

land region  12, 110land section  117large diameter extruders  132large diameter pipe extrusion 

206large differences in melt

temperature  208large sidegroup  64large volume compounding  165laser gage  54layer thickness  192layflat film  59L/D  4, 209L/D of the extruder  161LDPE  73, 145, 184, 194lead chromate  194leading side of the screw flight 

110leakage at seals  169leakage flow  92leaks in closed-loop systems 

168legs  113length of the compression

section  144, 162length-to-diameter (L/D) ratio 

4, 209LeRoy  103LeRoy mixer  104less restrictive die  171less restrictive screen pack  171,

172level of vacuum  124levels of crystallinity  65lifting techniques  132light colors  194, 198lightly colored plastics  123lights off  186light transmission  65linear plastics  141lines  145line speed  20, 115line tension  20, 128liquid crystalline plastics (LCPs) 

66LLDPE film  183

242  Index

loading pattern  202log-log plot  139longer extruder barrel  156long loose hair  131long residence times  147, 157long shaft wire brush  130loose boards  133loose clothing  131looseness in rotating machinery 

166loss of physical properties  145loss of volatiles  145low bulk density feed stock  171low cost fillers  180low-density polyethylene (LDPE) 

65lower critical shear rate  142lower mesh screens  172lower portion of the channel  95lower viscosity resin  193lowest viscosity  198low frequency instabilities  144low friction coating  85, 145, 171,

173, 174low friction screw coating  171,

172low melt index masterbatch  159low melt index material  123, 158low melting point plastics  126low melt temperatures  185low oil levels  165low output  139low speed extruders  3low-temperature gas stream 

206low temperature plastics  123low viscosity plastics  160lubricating effect  184lubricating oil  165lubrication  185

M

machine downtime  166machine geometry  77machine troubleshooting  164

Maddock  103Maddock mixer  104Maddock mixing section  157main drive  202main flight  105main power switch  124maintenance  138, 164, 166maintenance activities  164Maintenance Professional  164maintenance software  164maintenance tool  207mandrel  116manifold  12, 14, 117manifold system  178manual  203manual cleaning  195manual screen changers  11manual tuning  28manufacture  98manufacturing discipline  187marble  182Massachusetts Institute of

Technology (MIT)  182material blockage  172material change  158material choice  160material consumed in the

change-over  177material cost  180materials QC  138material stuck  172Maxflexx  205measurement  61measurement error  22, 25measurement of melt

temperature  160measure screws and barrels 

167mechanical degradation  146mechanical properties  160mechanical specific energy

consumption  177medical  132, 134medical tubing  14melamines  64

melt conveying  77, 86, 88, 89, 228

melt conveying problems  171melt conveying zone  90, 93melt displacement behavior  190melt-fed extruder  1melt film  85, 87, 226melt film thickness  87Melt Flipper  179melt flow index (MFI)  68melt fracture  141, 174, 183melt index (MI)  68, 138melt index tester  68melting  85, 226, 228melting capacity  88, 202, 209melting efficiency  87melting or plasticating  77melting point  71, 75, 138melting problem  140, 144, 171,

209melting rate per unit down-

channel distance  227melting related instabilities 

202, 209melting theory  226melt pool  35, 85, 88, 226melt pressure  19, 29, 30, 48,

128, 187melt pressure measurement 

135melt pump  179, 228melt strength  209melt temperature  19, 29, 35,

90, 104, 128, 160, 174, 175, 187, 189, 201, 214

melt temperature and pressure fluctuations  167

melt temperature differences  92

melt temperature distribution  38, 208

melt temperature fluctuation  214

melt temperature measurement  23

Index  243

melt temperature variation  38, 141, 143, 144, 208

melt viscosity  104, 138membership functions  28mercury  21, 31, 132, 135meshing gear teeth  165mesh number  10mesh value screens  156metal glass (Lunac)  198metallic particles  161metal particles  162, 173metal sheath  24metering section  109meter-weight of the pipe  204method of internal pipe cooling 

205methods to increase efficiency 

175mica insulated heaters  7Michaeli  120microcellular foam  182micron rating  10mid-region of the channel  90milieu  189minimum residence time  190,

191misalignment  166mixed alkyl-aryl phosphites  185mixing  10, 77, 86, 93, 158mixing capability  100mixing elements  92mixing screw  174mixing sections  10, 158mix quality  158mixture  158modular extruders  203moisture-induced degradation 

109moisture level of feed stock  187molecular weight  68, 184, 209molybdenum disulfide  183Monastral blue  194morphology  65motor  15motor bearings  169motor brushes  167

motor efficiency  167motor load  19, 29, 84, 126–128,

140, 161, 166, 187, 189, 214motor problems  143motor vibration  168movable guards  131moving parts  131MTC  166multi-flighted discharge  144multi-flighted screw  88multi-layered product  14multi-layer pipes  204multi-lumen tube  113multi-manifold system  14, 56multiple flights  88multiple haul-offs  180multiple knife cutter  60multi-screw extruder  2multi-strand extrusion  178multivariate analysis (MVA)  207municipal water  169MVA system  207

N

narrower pellet size distribution  188

natural bridge  79NCF (Nexxus Channel-F)  219neck ties  131neutral screw  9new developments in extrusion 

175Newtonian  70Newtonian fluid  104, 229Nexxus technology  219Niemeier  199nip roll  55, 59, 131nip roll section  54nitrided steel  185noise level  176noise level of bearings  168no material in the feed hopper 

171nominal speed  14non-catalytic steels  185

non-coated part of the screw  198

non-colored plastics  194, 198non-contact temperature

measurement  23non-foam extrusion  182non-insulated TC  25non-intermeshing  3non-isothermal analysis  38non-linear fluid  69non-Newtonian  69non-Newtonian behavior  90non-Newtonian fluids  104, 229non-Newtonian plastics  38, 142non-return valve (NRV)  215non-uniform flow  72, 201, 208non-uniform melt temperatures 

97, 179, 208non-uniform mixing  97non-uniform plastic tempera-

tures  72non-uniform temperatures 

201non-vented single screw

extruder  160no-output condition  171Noriega  209normal flow  92Novachem  198Nucrel Disco purge  196number of screens in the screen

pack  156nylon (PA)  65, 130, 142

O

objective  163observed and comparative facts 

163obstruction  133octahedral shape  60off-spec product  188oil  167oil cooling  8oil filter  169oil flow to all bearings  168

244  Index

oil heat exchanger  169oil leaks  168oil pump  165oil sump  169oil temperatures and pressures 

168on-off control  26on-off temperature control 

144onset of sharkskin  184on-the-fly adjustment of pipe 

204open discharge  140opening of a door  189operating conditions  77operating cost  217operating procedures  172, 175operator friendly  98operator skill  217optical properties  160Optifoam©  182optimizing the process  187optimum depth of the channel 

90optimum helix angle  90, 104optimum helix angle for melt

conveying  90optimum screw geometry  90organic acids  183organo-phosphates  185, 186organo-phosphite anti-oxidants 

185orientation  113original equipment manufacturer

(OEM)  89orthogonal arrays  207outer layer  92outer region  96outer vortex  206output  161output fluctuations  128output problems  139output stability  214output variation  17, 139, 144outside diameter  54

outside region of the channel  90

oven  129overheating of the plastic  201overloads  170over-pressure safety device  21,

125, 170over-pressure shutdown  32oxygen  73, 147ozone layer  183ozone treatment  56

P

packaging products  132Paetzold  197paper  57paperboard  57parallel screws  3parison  204partially filled  82, 109partially intermeshing  3partially streamlined dies  120particle rotation  214particle shape  78particle shape distribution  78particle size  78, 138, 157, 174particle size distribution  78parts  131Pascal · second  67passageways  133P-control  27PD-control  28PE  200, 205pellet concentrate  130pelletized resins  189pelletizers  60pelletizing system  60pellet size distribution  188performance improvement  138P-gels  157phosphoric acid  185phthalocyanines  194physical characteristics  138physically clean the extruder 

198

physical properties  181, 201, 218physical purging compounds 

130PID-control  28piezo-electric transducer  21, 22pigments  194pin barrel extruder  100pinholes  145, 146pin mixers  98, 99pin mixing sections  99pipe  12, 114, 181pipe extrusion  203pipe or tubing die  110pits  133plain weave  10planetary barrel section  105planetary gear extruders  102planetary gear mixers  105planetary screws  105plant voltage variations  20, 144plasticating extruder  1, 77plastic film  57plastic melt  63plastic properties  77plastic residue  130plastics extruder  1plastic temperature  8, 132plate die  119platinum resistance element  23plug  170plug flow  93, 191plugged filter  165plugging  89, 209PMEW  164pneumatic pressure transducer 

22point-of-operation guards  134Poise  67polishing rolls  54polyamide (nylon)  109polybutadiene  66polycarbonate (PC)  64, 109,

130, 198polyester  64, 105, 109, 142polyesters of oxiacids  184

Index  245

polyethylene  63, 64, 142, 147, 183, 185

polyethylene-based compounds  130

polyethylene glycol (PEG)  183polyethylene terephthalate (PET) 

65polyisoprene  66polymer feed port  218polymer header system  178polymerization  157, 173polymerization reactor  157polymer melts  208polymer processing aids (PPA) 

183polyolefins  180PolyOne  198polypropylene (PP)  64, 65, 177,

180, 181polystyrene (PS)  64, 76, 142, 177polyurethane  67, 105, 109polyvinylchloride (PVC)  64polyvinylidene fluoride  132Ponzielli  213poor melt temperature

measurement  172poor mixing ability  97poor screw design  201portable hand tools  135position of the interface  190,

193position of the pin  204position of the vacuum tank 

204post consumer reclaim (PCR) 

78post-reactor finishing  165post-treatment ovens  202powder  156powder coatings  105powder leaks  168power consumption  181, 187,

209, 214power draw  19power draw from the heaters 

128

powered industrial truck operators  134

power law approximation  70power law expression  70, 139power law fluid  70power law index  70, 90, 191power transmission capability 

16PP  200, 205PPA  184, 185pre-compounded material  183pre-control method  207pre-drying  174, 202 pre-dry the plastic  108preheating  58, 89, 202preheating the plastic  89, 162pre-heating zones  203preheat the plastic pellets  206pre-land section  117preparation of the machine  123pressure  127, 128, 132, 165 – feedback control  31, 32 – pulses  48

pressure and temperature regulators  168

pressure drop  98, 104pressure flow  91, 94, 229pressure fluctuation  144pressure generating capability 

18, 217pressure gradient  93, 193pressure indicator  169pressure indicators/controllers 

170pressure