Author: Peter S. Johnson

Publisher: Hanser Gardner Publications

Published: 2001

Total Pages: 145

ISBN-13: 9781569903094

1 Overview of Rubber Processing p. 1 1.1 Introduction p. 1 1.2 Testing p. 2 1.2.1 Raw Materials Quality Assurance p. 2 1.2.2 Processability Testing of Mixed Compounds p. 2 1.2.3 End Product Testing p. 3 1.3 Conclusion p. 3 References p. 4 2 Raw Materials Acceptance and Specifications p. 5 2.1 Introduction p. 5 2.2 Raw Materials Specifications p. 5 2.2.1 Elastomers p. 6 2.2.2 Fillers p. 7 3 Mixing of Rubber Compounds p. 9 3.1 Introduction p. 9 3.2 Material Flow to the Mixer p. 10 3.2.1 Receipt and Storage of Raw Materials p. 11 3.2.2 Feeding, Weighing, and Charging Raw Materials p. 12 3.2.2.1 Weighing Major Ingredients p. 14 3.2.2.2 Small Component Weighing p. 14 3.3 The Mixing Process p. 15 3.3.1 Incorporation p. 16 3.3.2 Dispersion p. 17 3.3.3 Distribution p. 19 3.3.4 Plasticization p. 20 3.3.5 Natural Rubber Mastication p. 20 3.3.6 Flow Visualization and Modeling of the Mixing Process p. 20 3.3.6.1 Flow Visualization p. 21 3.3.6.2 Modeling p. 21 3.3.7 Flow Behavior on Mills p. 24 3.4 Internal Mixers p. 26 3.4.1 Developments in Internal Mixers p. 29 3.4.1.1 Farrel Mixers p. 29 3.4.1.2 Kobelco Stewart Bolling Mixers p. 30 3.4.1.3 Krupp-Midwest Werner und Pfleiderer Mixers p. 31 3.4.1.4. Pomini Mixers p. 31 3.4.2 Choosing a Mixer p. 32 3.4.3 Inspection and Preventative Maintenance of Mixers p. 32 3.4.4 Internal Mixer Operation p. 33 3.4.4.1 Mixing Procedures p. 33 3.4.4.2 Temperature Control in Internal Mixers p. 37 3.4.4.3 Rotor Speed p. 37 3.4.4.4 Ram Pressure p. 38 3.4.4.5 Batch Size p. 38 3.4.4.6 Dump Criteria p. 40 3.4.5 Control of the Mixing Process p. 41 3.4.6 Scale-Up p. 41 3.5 Take-Off Systems p. 43 3.5.1 Dump Mills p. 43 3.5.2 Packaging p. 44 3.5.3 Single Pass Mixing p. 45 3.6 Other Mixing Equipment p. 45 3.6.1 Mill Mixing p. 45 3.6.2 Continuous Mixing p. 47 3.7 Custom Compounding p. 47 3.8 Troubleshooting the Mixing Process p. 48 3.8.1 Inadequate Dispersion or Distribution p. 49 3.8.2 Scorchy Compound p. 49 3.8.3 Contamination p. 49 3.8.4 Poor Handling on Dump Mill p. 49 3.8.5 Batch-to-Batch Variation p. 49 3.9 Concluding Comments p. 50 References p. 50 4 Flow Behavior of Compounds p. 53 4.1 Introduction p. 53 4.2 Fundamentals of Rheology p. 53 4.3 Effect of Compounding Ingredients on Processing Behavior p. 58 4.3.1 Elastomers p. 58 4.3.2 Fillers p. 59 4.3.2.1 Carbon Blacks p. 59 4.3.3 Plasticizers and Processing Aids p. 60 4.3.3.1 Plasticizers p. 61 4.3.3.2 Processing Aids p. 62 4.3.4 Elasticity p. 63 4.3.5 Conclusion p. 64 References p. 64 5 Testing of Compounds After Mixing p. 65 5.1 Introduction p. 65 5.2 Processability Test Instruments p. 68 5.2.1 The Mooney Viscometer p. 68 5.2.1.1 Delta Mooney p. 69 5.2.1.2 TMS Rheometer p. 70 5.2.2 Capillary Rheometers p. 80 5.2.3 Oscillating Disk Curemeters p. 73 5.2.4 Rotorless Curemeters p. 75 5.2.5 Dynamic Mechanical Rheological Testers p. 75 5.2.6 Stress Relaxation Instruments p. 75 5.2.7 ODR Cure Times Correlation with MDR p. 77 5.3 Comparison of Alpha Technologies Processability Test Instruments p. 78 5.4 Conclusion p. 80 References p. 80 6 The Curing Process p. 83 6.1 Introduction p. 84 6.2 Scorch or Premature Vulcanization p. 84 References p. 85 7 Calendering of Rubber p. 87 7.1 Introduction p. 87 7.2 Equipment p. 87 7.3 Processes p. 88 7.3.1 Feeding p. 88 7.3.2 Sheeting p. 88 7.3.3 Frictioning p. 88 7.3.4 Coating p. 89 7.3.5 Roller Dies p. 89 7.3.6 Downstream Processes p. 90 7.4 Modeling the Calendering Process p. 90 7.5 Troubleshooting Problems in Calendering p. 91 7.5.1 Scorch p. 91 7.5.2 Blistering p. 91 7.5.3 Rough or Holed Sheet p. 91 7.5.4 Tack p. 91 7.5.5 Bloom p. 91 7.6 Conclusions p. 91 References p. 92 8 Extrusion of Rubber p. 93 8.1 Introduction p. 93 8.2 Feeding p. 93 8.2.1 Cold-Feed versus Hot-Feed Extruders p. 94 8.3 Mass Transfer, Conveying, or Pumping p. 96 8.3.1 Flow Mechanism p. 97 8.3.2 Extruder Designs p. 98 8.3.2.1 The Maillefer Screw p. 99 8.3.2.2 The Iddon Screw p. 100 8.3.2.3 The Transfermix p. 101 8.3.2.4 The EVK Screw p. 101 8.3.2.5 The Pin Barrel Extruder p. 101 8.3.2.6 The Cavity Transfer Mixer p. 102 8.3.2.7 Vented Extruders p. 104 8.3.2.8 Dump Extruders p. 104 8.3.2.9 Strainers p. 105 8.3.2.10 Extruder Barrels p. 105 8.4 Extruder Operation and Control p. 105 8.5 Shaping p. 108 8.5.1 Extruder Heads p. 108 8.5.1.1 Coextrusion p. 109 8.5.1.2 Crossheading p. 109 8.5.1.3 Shear Heads p. 109 8.5.2 Dies p. 111 8.5.2.1 Pressure Drop p. 111 8.5.2.2 Die Swell p. 111 8.6 Take-Off and Curing p. 112 8.6.1 Continuous Vulcanization Systems p. 113 8.6.1.1 Pressurized Steam Systems p. 113 8.6.1.2 Hot Air Curing Systems p. 113 8.6.1.3 Hot Air Fluidized Bed Systems p. 114 8.6.1.4 Liquid Salt Bath Systems p. 114 8.6.1.5 Microwave Systems p. 114 8.6.1.6 Shear Head Systems p. 115 8.6.1.7 Electron Beam Systems p. 115 8.6.1.8 Steel Belt Presses p. 116 8.6.1.9 Ultrasonic Vulcanization p. 116 8.7 Troubleshooting the Extrusion Process p. 116 8.7.1 Low Output Rate p. 116 8.7.2 Poor Dimensional Stability of Extrudate p. 117 8.7.3 Excessive Heat Buildup in Compound p. 117 8.7.4 Rough Surface on Extrudate p. 117 8.7.5 Contamination p. 117 8.7.6 Porosity in Extrudate p. 117 8.7.7 Strip Difficult to Feed p. 117 8.7.8 Surging Output p. 118 8.8 Concluding Comments p. 118 References p. 118 9 Molding of Rubber p. 119 9.1 Introduction p. 119 9.2 Compression and Transfer Molding p. 120 9.3 Injection Molding of Rubber p. 122 9.3.1 Injection Molding Equipment p. 125 9.3.1.1 Delivery Systems p. 125 9.3.1.2 Nozzles, Runners, and Gates p. 127 9.3.1.3 Molds p. 128 9.3.1.4 Automatic Ejection p. 129 9.3.1.5 Deflashing p. 129 9.3.2 The Injection Molding Process p. 130 9.3.2.1 Injection Temperature p. 130 9.3.2.2 Screw Speed p. 131 9.3.2.3 Back Pressure p. 131 9.3.2.4 Injection Pressure p. 131 9.3.2.5 Summary p. 131 9.3.3 Monitoring and Modeling the Injection Molding Process p. 131 9.3.4 Control of the Injection Molding Process p. 132 9.3.5 Compounds for Injection Molding p. 133 9.3.6 Problems in Injection Molding of Rubber p. 133 References p. 136 10 Finished Product Testing p. 137 10.1 Introduction p. 137 10.2 Test of Filler Distribution and Dispersion p. 138 10.2.1 Microscopy p. 138 10.2.2 Surface Roughness p. 138 10.3 Tests on Cured Specimens p. 138 10.3.1 Tensile Tests p. 139 10.3.2 Hardness p. 139 10.3.3 Compression Set p. 139 10.3.4 Solvent Resistance p. 140 10.3.5 Aging p. 140 10.3.6 Ozone Cracking p. 140 References p. 140 Index p. 143.