Polyoxymethylene: Engineering Plastic for Precision Components
Polyoxymethylene (POM), commonly known by the trade names Acetal (homopolymer) or Delrin (copolymer), is a high-performance engineering thermoplastic renowned for its exceptional stiffness, dimensional stability, and low friction. It is a semi-crystalline polymer consisting of repeating -CH2O- units, resulting in a material that exhibits a unique combination of metal-like properties and plastic processability. POM is characterized by its high tensile strength and creep resistance, excellent resilience and fatigue endurance, and low moisture absorption, which allows it to maintain precise tolerances in humid environments. Furthermore, it has a naturally low coefficient of friction and good wear resistance, making it an excellent bearing and gear material. It is typically supplied in a natural white/opaque color and is available in both homopolymer and copolymer grades, with the copolymer offering improved thermal stability and chemical resistance.
The primary applications for POM are in precision mechanical parts that require long-term performance under load and friction. It is a cornerstone material for manufacturing gears, bearings, bushings, fasteners, and conveyor belt links in industries ranging from automotive (e.g., fuel system components, window regulators) and consumer appliances (e.g., gears in printers, kitchen utensil mechanisms) to industrial machinery and plumbing (e.g., valve bodies, pump impellers). Its low friction and wear properties often eliminate the need for external lubrication. While it offers excellent resistance to hydrocarbons and solvents, it has poor resistance to strong acids and bases. When compared to nylon (PA), another common engineering plastic, POM is stiffer, more dimensionally stable, and has lower friction, but is less tough and has a lower maximum service temperature, making material selection highly dependent on the specific mechanical and environmental demands of the application.