Ertacetal: The Differences and similarities between Acetal C and Acetal H

Within the plastic family, Ertacetal (Acetal) is a common name given to a family of thermoplastics. Its chemical name is known to be: "PolyOxyMethylene", or POM. Ertacetal is usually available in two resins: Copolymer acetal (POM-C), and homopolymer acetal (POM-H); commonly called Delrin®. At Ai Plastics, we offer both grades, in different sizes, cut to size.

The Differences

Ertacetal C (Acetal C)

This copolymer offers excellent performance at a slightly lower cost than Acetal H/ Delrin. The properties between the two grades are pretty much similar, however its low stress levels and high tensile strength assures flatness and dimensional stability to a maximum temperature of 100 degrees Celsius. At Ai Plastics, Ertacetal C is offered in both rods and sheets and are suitable for food applications as it is FDA approved. The material comes in both black and natural.

Other benefits include;

  • Better dimensional stability due to its lower level of crystallinity.
  • Better resistance to hot water and strong caustics, or high pH (basic) solutions.
  • Lower coefficient of friction and better impact and wear properties, especially in wet or moist environments.

Ertacetal H / Acetal

Ertacetal (Acetal) Homopolymer offer slightly higher mechanical properties other Ertacetal C. It offers a higher mechanical strength, stiffness, hardness and creep resistance as well as a lower thermal expansion rate and often also a better wear resistance than the Ertacetal copolymer. Some of the properties of Ertacetal H include:

  • Greater stiffness, with higher flexural modulus at room and elevated temperature applications.
  • Slightly higher tensile and impact strength at room temperatures and lower.
  • Slightly harder, thus giving the homopolymer acetals a lower coefficient of friction.


In most cases, Ertacetal (Acetal) homopolymer and copolymer can be interchanged because many material properties are approximately 10 % of each other. One of the most common characteristics in engineering plastic community is the ease of machining. Compared to other engineering plastics in the plastic family, Ertacetal C and Ertacetal H do not deflect away from nor do they easily chip, making it an ideal material for machining.

Both grades are known to have high mechanical strength, low thermal expansion, low water absorption and good creep resistance. It also has high lubricity which contributes to its high abrasion resistance and very low coefficient of friction.

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Typical Material Applications

Due to their various properties such as lubricity, strength, chemical resistance and ease of machining, Ertacetal (Acetal-C and Acetal-H) can be used in thousands of different applications. Common uses include:

  • Conveyor moving parts
  • Automotive and fuel related parts
  • Sliding and guiding parts
  • Gears
  • Bearings
  • Zippers
  • Electrical components and insulation
  • Winter sports equipment
  • Pump and valve parts

Find out more

If you need technical advice on Ertacetal C and Ertacetal H, please give us a call at 0161 727 0255 or download our datasheets from our website. You can also send your questions to



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