Polyoxymethylene (POM) plastic, commonly known as Acetal, is a high-performance engineering thermoplastic. It is widely used in applications demanding precision and durability. POM stands out for its ability to maintain structural integrity and functional performance under demanding conditions.
Understanding POM Plastic
Polyoxymethylene (POM) is a synthetic polymer, also known as Acetal, polyacetal, or polyformaldehyde. It is a thermoplastic polymer derived from formaldehyde, characterized by repeating -CHâ‚‚-O- units. This molecular structure gives POM a semi-crystalline nature, contributing significantly to its physical properties.
POM exists in two primary forms: homopolymer and copolymer. Homopolymer POM, known by the trade name Delrin, is formed by the direct polymerization of formaldehyde. Copolymer POM is produced by incorporating a co-monomer, such as trioxane, during polymerization. This chemical variation results in subtle property differences, with copolymers often exhibiting enhanced stability in certain environments.
Key Characteristics of POM
POM possesses properties that make it a material of choice for many engineering applications. It has high strength, stiffness, and rigidity, maintaining these attributes even in colder temperatures. This allows components to withstand considerable mechanical stress without deforming.
POM’s excellent dimensional stability means it reliably maintains its shape and size despite temperature or humidity fluctuations. This consistency is important for precision parts requiring tight tolerances. It also exhibits a low coefficient of friction and superior wear resistance, enabling parts to move smoothly and reducing degradation. This contributes to extended product lifespan and efficient operation in moving assemblies.
POM offers good chemical resistance, withstanding exposure to oils, greases, and many organic solvents without significant degradation. It also demonstrates low moisture absorption, preventing swelling or dimensional changes in humid environments. These attributes, coupled with its electrical insulation properties, make POM a versatile material.
Common Applications of POM Plastic
POM’s unique properties lead to its widespread use across diverse industries. In the automotive sector, POM is found in components like gears, bearings, fuel system parts, and interior trim. Its strength and wear resistance contribute to the longevity and reliable operation of parts subjected to continuous motion and varying temperatures.
Consumer goods use POM in items like zippers, buckles, and appliance parts. Its precision and durability ensure these products function smoothly and reliably. Industrial machinery incorporates POM into bearings, bushings, rollers, and conveyor belts, where its low friction and dimensional stability minimize wear and maintain operational efficiency.
In the medical field, POM is used in devices like insulin pens and surgical instruments. Its chemical resistance and the low porosity of copolymer variants make it suitable for applications requiring cleanliness and resistance to sterilization processes.
Considerations and Comparisons
While POM offers many advantages, it has specific considerations for its application. It is susceptible to degradation from prolonged ultraviolet (UV) radiation exposure, limiting its suitability for outdoor use without UV-stabilizing additives. Its flammability requires careful consideration during processing and in end-use environments. While generally chemically resistant, POM shows limited resistance to strong acids.
When comparing the two main types, homopolymer POM typically offers slightly higher mechanical strength and stiffness. Copolymer POM, however, provides enhanced chemical resistance, improved thermal stability, and often exhibits less centerline porosity, making it a preferred choice for food contact or medical applications. POM is often chosen as an alternative to metal components due to its comparable strength, low friction, and wear resistance, while offering the benefits of reduced weight and easier processing. It generally surpasses commodity plastics like polyethylene or polypropylene in mechanical performance and heat handling capabilities.