POM is characterized by its high strength, hardness and rigidity to −40 °C. POM is intrinsically opaque white, due to its high crystalline composition, but it is available in all colors. POM has a density of ρ = 1.410–1.420 g/cm3.[5]
POM homopolymer is a semi-crystalline polymer (75–85% crystalline) with a melting point of 175 °C (347 °F). The POM copolymer has a slightly lower melting point of 162–173 °C.
POM is a tough material with a very low coefficient of friction. However, it is susceptible to polymer degradation catalyzed by acids, which is why it is stabilized - both the homopolymer and the copolymer have chain end groups (introduced via end capping) that resist depolymerization. With the copolymer, the second unit is normally a C2 (ethylene glycol) or C4 (1,4-butanediol) unit, which is introduced via its cyclic acetal (which can be made from the diol and formaldehyde) or cyclic ether (e.g. ethylene oxide). These units resist chain cleavage, because the O-linkage is now no longer an acetal group, but an ether linkage, which is stable to hydrolysis. POM is sensitive to oxidation, and an anti-oxidant is normally added to molding grades of the material.