Polyoxymethylene (polyformaldehyde) thermoplastic crystalline polymer. Known as the "super steel" or "steel", also known as polyoxymethylene. English abbreviation is POM. In general, the polymers obtained by formaldehyde polymerization are not high in polymerization degree and easy to be heated and depolymerization. [POM is a smooth, shiny hard and dense material, light yellow or white POM is white powder, usually opaque, coloring is good, the proportion of 1.41-1.43 g / cm3, molding shrinkage 1.2-3.0%, molding temperature is 170-200 DEG C, 2 hours drying conditions 80-90 C. The long-term heat resistance of POM is not high, but it can reach 160 DEG C in a short time. Among them, the homopolymerization of POM is higher than that of copolymerization POM over 10, but the long term heat resistant copolymerization of POM is about 10 higher than that of homopolymerization POM. It can be used for a long time in the temperature range from -40 to 100 centigrade. POM is easy to decompose, the decomposition temperature is 280 DEG C, and there is irritation and corrosive gas in the decomposition. Therefore, the die steel should be made of corrosion-resistant material. 1 paraformaldehyde is a solid formaldehyde with high formaldehyde content, which is solid granular and easy to store and transport. Can be turned into formaldehyde vapor in high temperature, easy to replace high concentrations of formaldehyde in various reactions, is conducive to the application of chemical and pharmaceutical chemical synthesis and other industrial fields, especially in the synthesis of material requires the use of anhydrous formaldehyde, widely used. Mainly in the following aspects: (1) pesticide synthesis of acetochlor and Butachlor and glyphosate; (2) coating: paint with synthetic high-grade cars; (3): synthetic resin urea formaldehyde resin, phenolic resin, polyacetal resin, melamine resin, ion exchange resin and adhesive (4; synthetic paper) paper reinforcing agent; (5): casting foundry remover, synthetic casting adhesive; (6): aquaculture fumigation disinfectant. (7) organic raw material: used in the preparation of pentaerythritol, three hydroxymethyl propane, glycerin, acrylic acid, methyl acrylate, methacrylic acid, N - hydroxy - acrylamide, alkyl phenol, methyl vinyl ketone, etc.. (8) other: medicine and sterilization