POM plastic sample

Polyoxymethylene, often called Acetal, is one of the key engineering plastics. Among plastic materials, it is one with the most crystalline structure. Acetal is a good choice if low friction and good creep/fatigue resistance are required.

There are two types of POM: homopolymer (POM-H) and copolymer (POM-C). The difference between the two is not considerable. It is explained in this article by Hardie Polymers. The Plasticprop sample is a POM-C copolymer type.

Why choose POM?

  • Excellent bearing properties
  • POM has good fatigue and creep-resistance. POM is usually selected as the material for plastic springs, although any prolonged tension of the spring can not be recommended.
  • Retains its properties well in temperatures significantly below zero.
  • Excellent chemical resistance

Why not choose?

  • High shrinkage easily leads to warpage and dimension inaccuracy.
  • Due to small friction co-efficient, POM can be slippery to touch which can be a problem if you intend to use it for a handle.
  • Wear resistance is limited, although it is commonly mentioned as a strength of the material.
  • The surface appearance of POM components is typically oily.
  • POM is flammable; fire-retardant grades are difficult to find.

Typical applications:

  • Petrol tank lid in a car
  • Backpack snap harnesses
  • Plastic zippers
  • Pulley wheels
  • Gears

By examining the Plasticprop sample made of POM, you can draw for example the following conclusions:

  • Grip the sample tightly – you will notice how slippery it is compared with any other sample in the kit. POM makes for good bearing material.
  • When comparing the POM sample with glass-reinforced samples in particular, you can see that it is smaller. The shrinkage of POM is substantial.
  • Considerable corner effect and the slight distortion characteristic of semi-crystalline plastics can be noticed. The sink marks caused by ribs are also clearly distinguishable.
  • The filling window is almost completely filled; POM is more fluid than most other plastic materials. The fluidity also depends on the product grade used.
  • If you stress the sample’s creep indicator for several hours, you will see that POM also suffers from creep, even though it is known for its excellent creep resistance.
  • The sample surface is relatively clean, but ‘splashes’ typical for POM can be noticed around the injection point.
  • The surface of POM feels greasy. Printing on POM is difficult – test this by carefully scraping the stamp on the upper edge.
  • Scratches, especially on the rougher spark-eroded surface side, accompany smaller draft angles. This is somewhat surprising because you would expect POM to shrink apart from the scratching mould surface. Fair draft is recommended.
  • The integral hinge fills up and even functions for a short time before breaking off. For example, as an element facilitating assembly, the hinge could still function.
  • If you freeze the sample overnight, its feeling hardly changes. The properties of POM are maintained well at low temperatures.

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All information on Plasticprop.com is based on the best knowledge and understanding of experienced plastic product designers. Nevertheless, we may be wrong. Do not use this website as your primary or only source of information. Always check and test in practice. Kindly contribute, if you know better. We do not take any responsibility, financial or ethical, for the outcome of your product.