EXTRUSION

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EXTRUSION
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Overview of the process
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Overview
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Overview
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Overview
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Applications

• Compounding
• Profile
• A number of extrusion based processes

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Types of Extrusion

• Single screw
• Twin screw
• co-rotating, counter rotating

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Extrusion Screw
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Extrusion Screw
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Extrusion Screw
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Extrusion screw
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Screws for various processes
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Features of the screw
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Melting stages
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Screw Wear
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Extrusion Die
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Extrusion Die
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Extrusion Die
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Critical operation parameters

• Melt temperature
• Melt pressure
• Barrel temperature
• Die temperature
• Heater power
• Screw speed
• Line speed
• Finished products dimension
• Cooling rate

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Extrusion problems

• Melt fracture
• Sharkskin or alligator hide
• Uneven flow and surging
• Degradation
• Poor mixing
• Contamination
• Bubbles in extrudate

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Troubleshooting

• See Table 11.2 page 399

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Materials consideration

• Most thermoplastics
• Extrusion grade
• High MW, low MFI lt1
• Broad MWD
• Melt strength
• Some materials (like PVC) need lubricant
• Density differences can cause problems
• Fiber breaking

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Mathematical modeling

• Flow modeling in screw section
• Interaction of screw and die
• See page 383-389 of the text
• Commercial software

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Extrusion based processes

• profile, pipe tubing, wire coating, sheet
  flat film, blown film, coating, calendaring,
  fiber spinning, netting, co extrusion,