Polyoxymethylene

Polyoxymethylene, also known as polytrioxane and polyformaldehyde. The most important polyacetal resin, it is an engineering thermoplastic with good physical and processing properties. It is generally used for plastic gears and other mechanical parts because of its strength, impact resistance, and lubricity.

It is also found in formalin preserving solutions, since formaldehyde polymerizes in water. Formalin actually contains very little formaldehyde in the form of H₂CO monomer; most of it forms short chains of polyformaldehyde. A few percent methanol is often added to limit the extent of polymerization.

Synthesis

A solution of formaldehyde in water is first concentrated. When the water content is low enough, the solution is processed to form trioxane, to which dioxolane (from ethylene glycol) is added.

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• Properties