Acetal (Polyoxymethylene)

Acetal, or polyoxymethylene, refers to two distinct yet similar products: acetal homopolymer and acetal copolymer. The main molecular chain of acetal homopolymer is the backbone of the acetal copolymer chain, as acetal copolymer adds ethylene oxide randomly throughout the acetal homopolymer chain.

What are the properties of acetal?

The simple nature of the molecular nature of the acetal homopolymer chain allows a very stable crystalline structure. This crystallinity leads to high heat resistance, high modulus, excellent wear resistance, and resistance to solvents. The added ethylene linkages of acetal copolymer increase the thermal stability, elongation, and toughness but decrease the stiffness and strength. These changes are likely a result of the decreased crystallinity that results from adding the ethylene oxide groups to the molecular chain. The carbon to oxygen bonds in the main molecular chain are not as thermally stable as the carbon to carbon bonds found in other polymers. Thus, processing of acetal requires special attention to be paid to temperature during molding as exceeding the thermal degradation point (the temperature at which the material will begin to break down) will produce rapid decomposition resulting in formaldehyde gas. The temperature at which this degradation occurs is less for acetal copolymer than for acetal homopolymer.

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