Polyoxymethylene (POM) is categorized into two types based on the difference in its chemical structure within the molecular chain: homopolymer POM and copolymer POM. The key distinctions are as follows: homopolymer POM has high density, crystallinity, and melting point, but poor thermal stability, a narrow processing temperature range (about 10°C), and slightly lower acid-base stability; whereas copolymer POM has lower density, crystallinity, melting point, and strength, but good thermal stability, is not easily decomposed, has a wide processing temperature range (about 50°C), and better acid-base stability. It is an engineering plastic with comprehensive properties. It boasts excellent physical, mechanical, and chemical properties, especially certain ones. Commonly known as "Sai Gang" or "Duogang," it is the third-largest general-purpose plastic.A type of synthetic resin, also known as polyoxymethylene (POM) resin, POM plastic, or SAE steel material; it is a white or black plastic granule with high hardness, stiffness, and strength. Primarily used for products that serve as frameworks, such as gears, bearings, automotive parts, machine tools, and instrument interiors.