Material Description

Acetal (polyoxymethylene) is a semi-crystalline thermoplastic that is available in both copolymer and homopolymer grades (Delrin®), in addition to several filled Delrin® grades.  Acetal is easy to machine and offers good dimensional stability, high strength, and stiffness.

As a semi-crystalline material, Acetal is also characterized by a low coefficient of friction and good wear properties-especially in wet environments.

Because Acetal absorbs minimal amounts of moisture, its physical properties remain constant in a variety of environments.  Low moisture absorption results in excellent dimensional stability for close-tolerance machined parts.  In high moisture or submerged application, Acetal bearings outperform nylon 4 to 1.  Acetal is ideally suited for close tolerance mechanical parts and electrical insulators which require strength and stiffness.  It also offers resistance to a wide range of chemicals including many solvents.

PMI machines both homopolymer and copolymer grades of Acetal including enhanced bearing grade materials.  Acetron® GP POM-C Acetal is porosity-free and is an excellent choice for general purpose grade.  For slightly higher mechanical properties we offer and machine the homopolymer Acetal products.  For improved frictional properties, PTFE-enhanced Acetron® AF products are offered.

Notable Material Features

  • High mechanical strength, dimensional stability, and rigidity
  • Very low moisture absorption
  • Good wear and abrasion resistance
  • Wide range of chemical resistance (including hydrocarbons, neutral chemicals, and many solvents)
  • Natural lubricity

Grades Of Acetal

Acetal Copolymer (unfilled)

The copolymer grade offers excellent performance at a slightly lower cost than Delrin®.  Acetal copolymer may exhibit center line porosity, but porosity-free material is available.  Certain grades are FDA, USDA, NSF, Canada AG and 3-A Dairy compliant.  Low stress levels and high strength assure flatness and dimensional stability up to a maximum continuous service temperature of 180°F.


  • Problem: Dairy nickel and stainless blades were costly and expensive to fabricate.
  • Solution: Acetron GP POM-C porosity free POM-C plate is machined into scraper blades used in commercial ice cream manufacture.
  • Benefits: The porosity free Acetron ® GP POM-C blades are easily cleaned and do not entrap dirt or bacteria. The low stress level of Acetron® GP POM-C means parts that machined flat, stay flat.
  • Problem: Specialty metals and low-tech plastics don’t perform well in some moist environments.
  • Solution: Acetron® AF Blend POM-H excels in moist applications and offers longer part life.
  • Benefit: Acetron® AF Blend POM-H has a lower coefficient of friction than unfilled Acetal and lasts longer in most applications. It offers good stability and chemical resistance.
  • Problem: Clean in Place (CIP) equipment cleaning is a challenge for many metal gears.
  • Solution: Acetron® GP POM-C’s gears are easily fabricated and stand up to repeated cleaning cycles.
  • Benefits: Acetron® GP POM-C’s excellent chemical resistance, low internal stress and dimensional stability add up to better performance particularly in food processing and packaging applications.
  • Problem: Metal rollers in cargo truck lifts were being damaged in use.
  • Solution: Impact resistant Acetron® GP POM-C rollers absorb collisions with loading docks without deforming and causing the system to fail.
  • Benefits: Lighter weight and an ability to bounce –back made tight tolerance Acetron® GP POM-C rollers a better choice that other materials.

Tech Notes:

In general, Acetal does not perform as well in abrasive wear applications as nylons   Compensation for moisture related growth generally allows Nylatron®  nylons to be used for wet, abrasive applications. If your application requires dimensional consistency in an abrasive, high humidity or submerged environment, Ertalytye,® PET-P will often offer improved performance.

Delrin® is a registered trademark of E. I. du Pont de Nemours and Company.