POM
Polyoxymethylene (Acetal)
Glass Transition (Tg)
-60 to -50 °C
Melting Point (Tm)
165–175 °C
Density
1.41–1.43 g/cm³
CAS Number
9002-81-7
Recycling Code
♺ 7
Category
Engineering
Repeat Unit
–[CH₂–O]ₙ–
The repeating unit is the smallest structural fragment whose repetition builds the whole chain. Subscripts show the relative share of each unit in copolymers.
Key Properties
Highest crystallinity of common engineering plastics (~75 %); superb dimensional stability, low friction and fatigue resistance; depolymerises to formaldehyde if overheated.
Applications
Precision gears, zippers, fuel-system parts, snap fits.