Teflon vs Delrin (PTFE vs POM): Friction, Temperature, Strength, and Cost

Teflon is the DuPont-originated trade name for PTFE, polytetrafluoroethylene — a fluoropolymer whose carbon-fluorine bonds make it almost chemically inert and give it the slipperiest surface of any solid. It entered engineering through non-stick cookware, but its industrial value is in seals, valve components, chemical-handling parts, and electrical insulation. Virgin PTFE is white, waxy, dense (2.13–2.20 g/cm³), and mechanically weak: tensile strength of only 20–35 MPa with a modulus around 400–500 MPa — it bends like a stiff rubber, not like a structural plastic.

Delrin is DuPont’s trade name for acetal homopolymer (POM-H) — a highly crystalline engineering plastic built for mechanical work. At ~67 MPa tensile strength and roughly 3,000 MPa modulus, it is the closest common plastic to a machinable metal in feel: stiff, tough, springy, and fatigue-resistant, with a density of 1.42 g/cm³. It is the default choice for precision plastic parts — the same role we cover in our Delrin material guide and in the broader CNC machining materials overview.

The practical framing: PTFE is a surface and environment material; Delrin is a structure and precision material. Most Teflon-versus-Delrin decisions resolve themselves once you know which of those two jobs the part is doing.

Dry sliding. PTFE’s friction coefficient of 0.04–0.10 against polished steel is the lowest of any known solid — lower than wet ice on wet ice. Combined with its non-stick, non-wetting surface, this makes it the default for seals, backup rings, slide plates, wear strips, piston rings, and bushings that must run without lubrication. Food, pharmaceutical, and packaging equipment lean on it heavily because nothing sticks to it and nothing leaches out of it.

Heat. With continuous service at 260°C, short excursions above that, a melting point of 327°C, and useful properties down to cryogenic temperatures, PTFE covers a thermal range no other common machining plastic approaches. Delrin is out of the conversation above ~100°C.

Chemicals. PTFE is attacked by almost nothing — strong acids, bases, oxidizers, and solvents all leave it alone, which is why it lines reactors, seals pumps and valves, and carries aggressive fluids. Delrin handles fuels, oils, and many solvents well but is degraded by strong acids and oxidizing agents. Electrical: PTFE’s dielectric constant of ~2.1, extremely low dissipation factor, and enormous volume resistivity make it a premier high-frequency insulator — coaxial connectors and RF hardware are classic PTFE parts. Typical Teflon applications: seals and gaskets, valve seats and packings, chemical vessel liners, labware, non-stick surfaces, and electrical insulators.

Delrin is one of the most machinable plastics made. It cuts cleanly with standard carbide tooling, produces crisp broken chips, resists burring, and leaves excellent surface finishes straight off the tool. Because moisture uptake is low (~0.25% in 24 hours) and the material is stress-relieved in quality stock shapes, it holds dimension through machining and afterward. Tolerances of ±0.05 mm are routine; ±0.025 mm is achievable with temperature control and finish-pass discipline. Feed, speed, and tool geometry all behave predictably — Delrin is the plastic shops quote with confidence.

PTFE machines easily but not precisely. It is soft and cuts with very little force, so material removal is fast — but it smears and burrs at anything less than a razor edge, deflects away from the tool, and has a high coefficient of thermal expansion, so heat from cutting shifts dimensions measurably. Clamping must be gentle and distributed, or the part takes a set. And because PTFE creeps, features measured in the machine can drift afterward. The practical tolerance floor on critical PTFE features is around ±0.1 mm unless the shop plans temperature-soaked finishing passes and post-machining stabilization. Annealing or stress-relieving between roughing and finishing helps on tight work.

For process-level guidance across the full plastics family — stock forms, fixturing, chip control, and finishing — see our machinable plastics overview. The short version: quote tight-tolerance plastic parts in Delrin, and reserve PTFE for parts whose tolerances its surface properties can afford.