Full definition
Polyoxymethylene — an engineering thermoplastic with exceptionally low friction coefficient (0.1-0.3 against steel), high stiffness (elastic modulus 2.8-3.5 GPa), excellent dimensional stability, and outstanding fatigue endurance. Two types: homopolymer (Delrin by DuPont, slightly harder and stronger) and copolymer (Celcon/Hostaform, better chemical and thermal resistance). Properties: tensile strength 60-70 MPa, continuous service temperature -40 to +100°C, moisture absorption <0.2% (very low for engineering plastics), excellent machinability. Per ASTM D4181. Applications: precision gears, bearings, bushings, cams, rollers, conveyor guides, snap-fit connectors, valve bodies, and pump components. Limitations: poor UV resistance (requires stabilizers or painting for outdoor use), flammable (V-2 UL 94 without FR additives), attacked by strong acids. Competes with nylon (PA) but offers better dimensional stability in humid environments.