POM - properties, experiences and useful links
Polyoxymethylene, often called Acetal, is one of the key engineering plastics. Among plastic materials, it is one with the most crystalline structure. POM is known for its good fatigue/creep resistance, low friction and good performance in cold temperature. But the key characteristics of POM have been posted in several web pages already, so instead of posting them yet again I rather recommend a few good links. As a source of information for the strengths and limitations of POM I recommend:
- The RTP-company page on POM. gives a good overlook at the stenghts and limitations of the material.
- Omnexus polymerselector. and POM Center provides material data and cases. Note that gaining access to more detailed information might require signing in, which is free. The offered newsletter is published very often, however, so consider if you really want that before subscribing to it.
- Apart from listing the material properties, RTP-company provides some interesting case-studies.
- One look at the benefits and characteristics of POM in the Hardie Polymers blog article Does POM stand for "Plastics Outperforming Metals"?
- POM is available in homopolymer and copolymer grades. The difference between these can be read in Polyacetal (POM): When to Select Homopolymer or Copolymer?
- Dupont provides a comprehensive design guide for Delrin including very useful diagrams that are rarely available. Even though the material is limited to one POM-homopolymer product family of one manufacturer, the guide gives a good picture of POM characteristics in general.
- In case of POM copolymer, Designing with Celcon by Ticona might be useful.
Practical experiences of POM:
(For confidentiality reasons I can seldom post pictures of my own projects)
- POM felt like a suitable material for a tool handle that needed to slide over an aluminum bar. It served this purpose well, but the handle itself was so slippery that it was very difficult to have a good grip of it.
- POM is often used for different types of pulleys and wheels. In one case the pulley worked fine until winter came and the temperature sunk below zero. Because of the high thermal expansion tendency of POM, the pulley shrunk around the metal-bolt that was used as an axis. Even though POM retains its performance in cold conditions, the thermal expansion is clearly important to take into account.
- The functional properties of POM seemed perfect for an industrial application but due to the product specific flammability standard classification requirement UL94-V0, POM was not chosen. If the requirement is higher than HB, the suitability of POM is worth evaluating in an early phase.
- POM was selected as the material for a product that was subjected to cyclic loading because of its good fatigue resistance. The products however appeared to wear down quite rapidly, so the material was changed to PBT. As a result the lifetime of the product doubled. The fatigue resistance of PBT was sufficient for the application but wear resistance considerably better than before.
I’ll add more links to the page every time I run into something useful. If you have a good link, case or story in mind, please email me at firstname.lastname@example.org or add it below in comments.
To fully grasp the look and feel of POM order Plasticprop Essentials sample kit including 20 of the most common plastics. It has been carefully designed to convey and explain the characteristics of each material. Read here what the sample tells about POM.