Polyoxymethylene (also known as Acetal)

Symbol: POM
Crystallinity: Crystalline
Trade Names: Delrin-(H); Celcon-(C); Ultraform-(C)

Learn more about Polyoxymethylene.


POM Cog Fotolia_50376632_S.jpgPolyoxymethylene (also know as Acetal) is available in a homopolymer and a copolymer. The HOMOPOLYMER is a dense, highly crystalline material and is the stiffest and strongest of all non-reinforced thermoplastics. The COPOLYMER is not quite as tough but more resistant to chemicals. Both are dimensionally stable with low coefficient of friction.

Processing Considerations:

  • Residence Time: Residence time ranges from 2 to 4 minutes.
  • Back Pressure: Keep back pressure at 150 PSI (or 1500 plastic pressure) or less.
  • Drying: Both are not hygroscopic and do not require drying. However, drying can help part appearance.
  • RPM: RPM is typically 30 to 150.

Screw Design Based on:

  • Medium Compression Ratio
  • Medium Transition Length
  • Shallow Meter Channel Depth

Other Information:

  • Mixer: A low shear, mixing screw can be used to run POM. Reiloy Westland Corporation’s Eagle mixer has been proven to successfully process this resin.
  • Barrier: Barrier screws are not recommended.
  • Custom Design: A custom screw designed for POM is recommended over a general purpose screw.
  • Recommended Valve: A three piece free-flow or three piece locking valve is recommended.
  • Screw & Barrel Material Recommendation: When the homopolymer decomposes at 465°F, formic acid is formed which is corrosive, and toxic formaldehyde gasses are emitted. Corrosion resistant materials are preferable for barrels, screws and valves.

COPOLYMERS should be run on compression ratio’s ranging from 2.5 to 3.0.

Various additives and/or fillers can have an effect on a resin’s process behavior. For more detailed information, please contact Reiloy Westland Corporation.

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Industry Applications - Resins

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