POM-H vs POM-C: Key Differences & Best Uses
POM-H is homopolymer acetal—pure polyoxymethylene with maximum stiffness and creep resistance. POM-C is copolymer acetal, blended with ethylene oxide to boost chemical and thermal stability while slightly lowering hardness.
Buyers confuse them because both look ivory-white and machine like metal. Engineers pick the wrong rod, machinists see warping, and purchasers blame the supplier. The real split happens at the quote stage: one letter “H” or “C” can shift cost and performance.
Key Differences
POM-H: 0.2 % higher crystallinity, tensile strength ~70 MPa, melts at 175 °C, vulnerable to hot water and strong acids. POM-C: tensile ~65 MPa, melts 165 °C, shrinks less, stands up to alkaline cleaners and fuels. Machining: POM-C chips cleanly; POM-H can gum at high feeds.
Which One Should You Choose?
Pick POM-H for high-load gears, timing screws, and precision bushings needing minimal wear. Go POM-C for fuel-metering valves, food-handling star wheels, and parts exposed to steam sterilisation. If you’ll CNC thin walls, POM-C forgives chatter; POM-H demands rigid setups.
Can I weld POM-H and POM-C together?
No—differing melt temps and crystallinity create weak, brittle joints. Use mechanical fasteners or adhesive instead.
Does colour indicate grade?
Not reliably. Both are naturally white; dyes hide the letter, so always check the datasheet.