Acetal, Delrin AF, and PTFE: Premium Plastic Bearing Materials

Acetal, Delrin AF, and PTFE are among the most reliable plastics for high‑performance bearings, gears, and slide plates. Acetal and its DuPont brand, Delrin®, are thermoplastics that melt and retain their shape when cooled. PTFE, the lowest‑friction plastic known, is not a thermoplastic but can be extruded into high‑quality components. These materials excel where smooth sliding action and durability are essential.

Acetal, also called polyoxymethylene (POM), is a semi‑crystalline thermoplastic. Delrin® is a homopolymer version of Acetal, available in black and white. Unlike Acetal, Delrin typically exhibits centerline porosity, visible as a white stripe in molded sheets. Both materials meet FDA and 3A (Dairy) compliance standards.

Delrin melts at 175 °C, while the POM copolymer melts slightly lower, between 162 °C and 173 °C. Acetal’s very low coefficient of friction makes it ideal for light‑duty bearings. Though the homopolymer and copolymer look similar, their properties diverge: the copolymer offers superior thermal performance, impact resistance, wear resistance, chemical resistance, and lower water absorption. The homopolymer’s high crystallinity yields greater mechanical strength and creep resistance, but it is less tolerant of oxidizing agents and strong acids. The copolymer is favored in applications with moisture exposure, such as faucets, impellers, pump parts, and value stems.

Delrin AF combines 10‑25% oriented PTFE fluorocarbon fibers uniformly dispersed in Acetal/Delrin resin. The result is a material that retains Acetal’s strength, toughness, and dimensional stability while incorporating PTFE’s exceptional slipperiness. PTFE, commonly known as Teflon®, is the non‑stick material in cookware. Bearings made from Delrin AF sustain high operating loads at high speeds with minimal wear.

These non‑lubricated bearings eliminate slip‑stick behavior, as static and dynamic friction coefficients are equal. Slip‑stick—an intermittent jerking motion—can be compared to seismic fault slips. PTFE bearings are maintenance‑free; no additional lubrication is required. PTFE also boasts one of the highest continuous service temperatures among plastics.

Applications span tiny plastic gears in watches, garden hose nozzles, knife handles, pump parts, zippers, ball bearings, fasteners, ski bindings, acoustic guitar picks, and more.

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