What is Polyoxymethylene?

What is Polyoxymethylene Made of?

Polyoxymethylene is a polymer formed through the polymerisation of formaldehyde. It comes in two main types: homopolymer and copolymer. In industry, the material is often referred to as Acetal (copolymer) and Delrin (homopolymer).

Homopolymer has a more crystalline structure, which provides slightly higher mechanical strength, whilst copolymer offers better chemical stability and resistance to hydrolysis in hot water. The choice between these depends on the specific requirements of the intended application.

What Properties Does POM Have?

The material’s popularity is based on a unique combination of physical and chemical properties that make it suitable for various environments. These properties are:

• High wear resistance and low friction: This ensures that components suffer minimal wear even during constant movement against other surfaces.
• Good dimensional stability: unlike many other plastics, POM does not change shape to any significant extent under mechanical stress or temperature changes.
• High rigidity and strength: The material can withstand high forces without permanent deformation.
• Low moisture absorption: POM absorbs very little water, meaning its mechanical properties and dimensions remain stable even in humid environments.
• Good chemical resistance: It withstands most solvents, oils, and fuels very well.

Common Applications for POM

Thanks to its properties, POM is used in almost every engineering sector, from the automotive industry to medical technology. Examples of applications include:

• Gears and drive wheels: the low friction and high rigidity make the material suitable for mechanical power transmission, where quiet operation is required.
• Sliding bearings and bushings: here, the material’s natural wear resistance is utilised to reduce the need for external maintenance.
• Valve parts and pump housings: thanks to low moisture absorption and chemical resistance, POM performs well in contact with liquids.
• Machinery components: in the food and process industries, blue-coloured POM materials (POM Metal Detectable) are often used to facilitate visual detection and ensure hygienic operation.

Advantages of POM

Choosing POM over other materials can offer significant advantages in both design and operation. By replacing heavy metal components with plastic, weight can be reduced considerably, leading to lower energy consumption in moving systems.

The material’s ability to operate without external lubrication reduces maintenance costs and eliminates the risk of contamination in sensitive processes. During machining, POM enables very tight tolerances and a fine surface finish, which is a requirement for precision components.

Disadvantages and Limitations

To make the correct choice of material, one must be aware of its limitations. POM has limited resistance to UV light, which means it can degrade and become brittle when used outdoors for long periods without protective additives.

The material should not be used in applications involving very high continuous temperatures, as its mechanical strength diminishes. It is also sensitive to strong acids and oxidising agents. An objective analysis of the operating environment is necessary to ensure that POM is the right choice.

The Difference Between POM and Other Plastics

When compared with polyamide (PA/nylon), POM has better dimensional stability as it does not absorb moisture in the same way as nylon. This makes POM a better choice for precision parts in humid environments.

Compared to PTFE (Teflon), POM has significantly higher mechanical strength and stiffness, although PTFE has even lower friction and higher temperature resistance. POM is often the best compromise when a combination of mechanical strength and good sliding properties is required.

When is POM the Right Choice of Material?

POM is the right choice when the application requires high precision, low friction, and good mechanical stability over time. It is particularly suitable for moving machine components, precision engineering, and parts used in the process industry.

The choice of plastic should always be based on the specific application and its unique requirements. To ensure optimal performance in your design, we recommend consulting a materials expert early in the project phase.

Would You Like to Know More?

If you have any further questions or concerns regarding polyoxymethylene (POM), you are always welcome to contact us, and we will be happy to tell you more!