EXTRUSION
Applications Compounding Profile
Types of Extrusion Single screw Twin screw co-rotating, counter rotating
Extrusion Screw
Extrusion Screw
Extrusion Screw
Extrusion screw
Screws for various processes
Features of the screw
Melting stages
Screw Wear
Extrusion Die
Critical operation parameters Melt temperature Melt pressure Barrel temperature Die temperature Heater power Screw speed Line speed Finished products dimension Cooling rate
Sharkskin or alligator hide Uneven flow and surging Degradation Extrusion problems Melt fracture Sharkskin or alligator hide Uneven flow and surging Degradation Poor mixing Contamination Bubbles in extrudate
Materials consideration Most thermoplastics Extrusion grade High MW, low MFI <1 Broad MWD Melt strength Some materials (like PVC) need lubricant Density differences can cause problems Fiber breaking
Extrusion based processes Other extrusion based processes include: profile, pipe & tubing, wire coating, sheet & flat film, blown film, coating, calendaring, fiber spinning, netting, co extrusion