POM - Polyacetal (Delrin)

POM homopolymer (e.g., Delrin) offers higher mechanical strength, stiffness, impact resistance, and a higher melting point (178°C vs. 165°C). POM copolymer (e.g., Celcon, Hostaform) provides better thermal stability during processing, superior resistance to hot water and alkaline environments, less centerline porosity in thick sections, and wider processing windows. Homopolymer is preferred for maximum mechanical performance, while copolymer is favored for plumbing, hot-water applications, thin-walled parts, and long hot-runner processing.

Syntex America supplies a complete range of polyacetal grades including standard homopolymer POM for maximum mechanical strength, standard copolymer POM for broad processing and hot-water applications, low-friction PTFE-filled POM for enhanced sliding performance, UV-stabilized POM for outdoor applications, and glass-fiber-reinforced POM for increased stiffness and heat deflection temperature.

POM offers several advantages over nylon (PA) for gear and bearing applications: significantly lower moisture absorption (0.22% vs. 1.6–2.5% for PA6), meaning POM parts maintain dimensional accuracy in humid environments without swelling. POM also has a lower and more consistent coefficient of friction, better dimensional stability, higher stiffness, and superior fatigue resistance. Nylon is preferred when higher impact strength or chemical resistance to fuels is the primary requirement.

Yes, select POM grades are approved for food contact under FDA 21 CFR 177.2470 and for potable water system components under NSF/ANSI 61. POM is widely used in coffee machine components, food dispensing mechanisms, water filter housings, and plumbing fittings. Copolymer grades are generally preferred for hot-water contact applications due to their superior hydrolysis resistance compared to homopolymer.

POM has limited UV resistance and will degrade with prolonged outdoor exposure; this is addressed with UV-stabilized grades. POM is not resistant to strong acids and oxidizing agents, which limits its use in aggressive chemical environments. It has relatively high shrinkage (1.8–2.5%) that must be accounted for in mold design. POM is difficult to bond with adhesives or paint due to its low surface energy, though plasma treatment can improve adhesion. For applications requiring flame retardancy, POM is challenging to formulate to UL 94 V-0, so alternative materials like PBT or PA may be more suitable.