Polyoxymethylene (POM) Polyoxymethylene

Characteristics of POM Polyoxymethylene has almost no branches in the molecular chain, and only hydrogen atoms are present on the carbon atoms, resulting in high structural regularity. Compared with polyethylene, polyoxymethylene has short carbon-oxygen bonds, high cohesive energy density, compact aggregation, high crystallinity, and excellent rigidity and mechanical strength.

Polyoxymethylene generally includes homopolymers and copolymers. The tensile strength of homopolyoxymethylene can reach 68.9 MPa, and the tensile strength per unit mass is higher than that of zinc and brass. After tensile orientation, a 3 mm diameter filament can withstand a tensile force of about 104 N, and its tensile strength and modulus are close to steel.

In addition, POM also has outstanding advantages such as low friction coefficient, good wear resistance, no oil lubrication, good resistance to organic solvents, and low water absorption.

However, the thermal stability is poor, the temperature exceeds 230°C and it is easily decomposed, and the acid resistance is also poor.

The POM production method is different from the production method of polyoxymethylene and polyacetal:

1 Polyoxymethylene, prepared from formaldehyde as a monomer. The raw material formaldehyde often contains a large amount of water, formaldehyde and other impurities, which need to be refined to obtain high-purity formaldehyde. The formaldehyde is introduced into an inert solution containing a cationic catalyst (such as boron trifluoride **complex) to form a homopolyoxymethylene. In the presence of acetic anhydride, the terminal hydroxyl group is esterified to obtain a thermally stable polyoxymethylene, and then an auxiliary agent such as an antioxidant is added to form a homopolyoxymethylene product.

2 acetal copolymer, mainly made by copolymerization of trioxane. Concentration of 65% to 70% of formaldehyde, trioxane and high-purity products are obtained under the catalysis of strong cation or cation exchange resin, and the latter is opened with a small amount of comonomer (such as dioxolanes) in the presence of Lewis acid. Polymerization is polyoxymethylene. Most of the polymerization methods are bulk polymerization and twin screw extruders are used. Most of the copolymerized formaldehyde chain ends are hemiacetal end groups, which are extremely unstable to heat and need to be subjected to end-capping stabilization treatment to become a thermally stable polyformaldehyde. Then, additives such as antioxidants are added to granulate the copolymerized formaldehyde products. .

POM processing and application Polyoxymethylene can be processed into finished products by molding methods such as injection molding, extrusion and blow molding. It can also perform secondary processing such as machining, welding and electroplating. Polyoxymethylene products are divided into injection, extrusion and blow molding grades according to the viscosity. Through blending, strengthening and alloying, they can produce high flow, high rigidity, antistatic, electroplating, weather resistance, super toughness, etc. Sex varieties to meet different application requirements.

POM is mainly used in electronics, automotive, building materials, light industry and other industrial sectors for sealing rings, reels, gears, bearings, sliders, valves, keyboards, switches, zippers and handles and other parts. Zipper - the greatest invention of the 20th century.