Acetal vs PTFE: which should you specify?
The short answer: specify acetal (POM) for precise mechanical parts that carry load, and PTFE where heat, chemicals or the lowest possible friction decide the matter and the loads are light. Where a part needs both, a filled PTFE grade is usually the bridge.
At a glance
| Property | Acetal (POM) | PTFE |
|---|---|---|
| Strength & stiffness | High — one of the stiffest unfilled engineering plastics; resists creep | Low — soft, and deforms under sustained load (cold flow) |
| Friction | Low — typically 0.2–0.35 against steel | Among the lowest of any solid — typically 0.05–0.10 |
| Wear under load | Good in dry-running gears, cams and bushes | Poor when unfilled; glass, carbon or bronze filling improves it markedly |
| Temperature | To roughly 90–100 °C continuous | Roughly −200 to +260 °C |
| Chemical resistance | Good with fuels, oils and most solvents; attacked by strong acids and oxidising agents | Virtually inert to industrial chemicals and solvents |
| Moisture | Very low uptake (about 0.2%) — dimensionally stable | Effectively zero |
| Machining & tolerance | Excellent — cuts cleanly and holds tight tolerance | Machines easily, but softness and high thermal expansion make tight tolerances harder to hold |
| Relative material cost | Moderate | Higher |
Figures are typical values for unfilled grades and vary by grade and manufacturer — confirm against the supplier datasheet for a critical application.
Where acetal is the better choice
Choose acetal when the part carries load and must keep its shape: spur gears, cams, bushes, rollers, spacers, and snap-fit or threaded features. It is stiff, resists creep, absorbs almost no moisture and machines to tight tolerance, so a fit that is right on the day it is made stays right in service. Its limits are temperature — it is not a material for sustained duty much above 100 °C — and strong acids or oxidising chemicals, which attack it.
Where PTFE is the better choice
Choose PTFE when the environment, not the load, is the problem: seals, gaskets, valve seats, chemical-handling components, non-stick surfaces and electrical insulation. It stays serviceable from cryogenic temperatures to around 260 °C, is inert to almost every industrial chemical, and has the lowest friction you can specify. What it cannot do is carry sustained load without deforming — unfilled PTFE creeps, and it wears quickly in rubbing contact.
Filled PTFE — closing the wear gap
Where a part needs PTFE-level friction or chemical resistance and must also resist wear or creep, filled grades are the usual answer. Glass, carbon, graphite and bronze fillers raise wear resistance and stiffness considerably. The trade is that a filler gives up some of the chemical inertness and purity of virgin PTFE, and bronze-filled grades are not suitable for every chemical or food-contact duty — so the filler has to be chosen against the application.
How to decide
- Does the part carry sustained load or need a tight tolerance? Acetal.
- Will it run above about 100 °C, or at very low temperature? PTFE.
- Is it exposed to strong acids, oxidisers or aggressive solvents? PTFE.
- Is it a seal, seat or gasket rather than a structural part? PTFE.
- Does it need PTFE-level friction and wear life together? A filled PTFE grade.
Related comparisons
Final material suitability depends on the component drawing, load, speed, operating temperature, chemical exposure, food-contact requirements, wear conditions and validation. Tell us the position the part runs in and we will manufacture to the grade your drawing specifies — or discuss the material if the drawing leaves it open. See the full materials list for designations and characteristics.
Not sure which grade suits your part? Send the drawing and we’ll advise.
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