Home > Knowledge > Polyacetal (POM): When to Select Homopolymer or Copolymer?

Polyacetal (POM): When to Select Homopolymer or Copolymer?

The production of stable thermoplastics from formaldehyde was discovered around 60 years ago, using two independent approaches.  To prevent unzipping of the polymer chains at high temperature, DuPont used an end cap mechanism. Celanese opted for incorporation of a comonomer which also stopped the unzipping.  Today you still have a choice between the homopolymer grades and the copolymer grades of polyacetal (POM) but are they totally interchangeable?

Polyacetal pics

For most of the attributes of polyacetal, they are similar —: hard, tough, low coefficient of friction, good wear resistance, excellent fatigue endurance.  They are both opaque, with poor uv resistance, prone to thermal degradation, easily attacked by acids and alkali and have poor fire performance.

However there are subtle differences.  Homopolymers tend to have higher crystallinity levels. Hence they have better short term mechanical properties — stiffness, tensile strength, impact resistance and initial creep resistance. Copolymer grades have better oxidation resistance and exhibit better resistance to creep and creep rupture at longer time scales.  Surprisingly, glass fibre filled copolymer grades have better mechanical properties than the corresponding homopolymer. This is because the slightly different chemical structure gives better coupling to the glass fibre.

Having lower crystallinity, copolymers tend to have better dimensional stability and win out on lower friction and less wear.  Although homopolymer grades have a lower moisture uptake, the copolymer is less susceptible to hydrolysis in hot water. Likewise copolymers have better resistance to alkali materials.  Because of the higher crystallinity, homopolymer has a higher heat distortion temperature but copolymer grades have higher continuous use temperatures because of better long term stability.

For processors, the copolymer grades are attractive because of the lower process temperature associated with lower crystallinity and also a wider process window.

Trade names:

Homopolymer: Delrin,

Copolymer:     Celcon, Hostaform, Kepital, Lucel, Schulaform, Tecaform, Ultraform

This Polyacetal article was written by Dr.Charlie Geddes for Hardie Polymers

For more of Charlie’s blogs why not read more of our knowledge base articles?

For information on all the specified grades that we can offer please contact us today or try our polymer search.


Posted in Manufacturing,

Find the exact grade you require

Improve on your current price

Get the material you need faster

Our no risk Polymer Search

  • We’ll conduct a no obligation search so you don’t have to
  • We can supply the exact grade you need so you can meet your spec
  • Minimum quantity is just 25kg so you can get just what you need
  • If we can’t find your grade of plastic there is no cost to you
  • Products can be dispatched by express shipping if required

Chat to us first as we’re happy to answer any of your questions.


Request a Quote

  • Our team are available from 8am-5pm and we always aim to get back to you the same day. If you would rather contact us immediately please join us on live chat
    or give us a call on 0141 952 1900.
  • This field is for validation purposes and should be left unchanged.