Plastic vs Steel Bearings in Chemical, Food-Grade and Submersible Service: When PEEK, POM or PTFE Is the Right Call

Does the environment rule steel out before you compare anything else?

In food, chemical and submerged service the binding constraint is often not load but lubrication and corrosion. Where a washdown line prohibits traditional lubrication, the sources recommend engineered polymers including PTFE and PEEK.

They also flag molybdenum-containing grease as a contaminant risk in cleanroom and food-processing environments^15,23. That combination — no grease allowed, product contact possible — decides the material class before you examine load at all.

Corrosion points the same way in wet service. Stainless steel is recommended for moisture and mild chemicals, and 440C resists fresh water and mild chemical environments.

Polymers are recommended where steel would rust^19,23,25. Note the boundary: the sources describe stainless as a top choice for food processing and medical equipment, so a polymer is not automatically required in every food or chemical duty¹⁶.

A washdown food line is the case the sources use: traditional lubrication is prohibited. So a self-lubricating PTFE or PEEK bearing is the recommended direction, and any molybdenum-bearing grease is ruled out as a product contaminant^15,23.

If your process allows a food-grade lubricant and the chemistry is mild, stainless remains on the table and the decision moves to the later steps.

Does the polymer clear the temperature profile — and is steel's real limit its seal?

Polymer life is a function of temperature and exposure time, not a single ceiling. One source reports that a PA66-GF25 polymer cage gives at most 10 hours at 240°C with mild lubricants but more than 1,000 times that life below 100°C.

That same source reports that aggressive lubricants can cut cage life by a factor of 10⁹. So the number that matters is your continuous temperature history, not the peak.

On reported ceilings, PTFE reaches 260°C and PEEK 250°C continuous, both with excellent chemical resistance and low friction²⁰. Standard bearing steel is reported at about -30°C to +120°C, heat-stabilised steel toward +150°C, and the rubber seals on a standard 2RS bearing are usually the real limiting factor at about 100–120°C¹⁹.

That means a hot steel assembly may fail at its seal long before its steel does — a distinction worth checking before you reject steel on temperature alone. One caution on the comparison: 440C stainless is also reported at 250°C continuous, so the polymer ceiling is not higher than the stainless ceiling²⁵.

The polymer advantage is self-lubrication and corrosion resistance, not a temperature edge over stainless. The sources do not establish allowable continuous temperature for a complete plastic bearing under load, so treat the 250–260°C figures as material capabilities and confirm the loaded rating with the supplier.

Does the load and speed profile keep the polymer inside its PV limit?

The sources place polymer bearings in light-duty, PV-limited service. Engineered polymer plain bearings and bushings are recommended for washdown and food use, but their pressure-velocity limits must be strictly observed²³.

Polymers such as POM and nylon are described as lightweight, self-lubricating and quiet, used in light-duty applications like office equipment and conveyors¹⁶. Steel life, by contrast, is described through the L10 formula, L10 = (C/P)³ × 1,000,000 revolutions, with the static rating C0 mattering for dwell or shock loads¹¹.

The sources publish no load ratings for PEEK, POM or PTFE bearings, so no quantitative load comparison can be made here. What you can do is work the load and speed profile first, then let environment and mounting constraints narrow the choice.

Check standard catalog availability before considering a custom design²⁹. Heat is the second limit.

Plastics conduct heat poorly, so high-speed or high-friction operation can soften, distort or melt the bearing. The sources suggest cooling measures such as forced air, heat sinks or thermal spacers, or hybrid plastic-with-metal-backing designs³⁴.

If your duty is not light, a polymer is the wrong starting point regardless of how well it resists the chemistry.

Will the polymer hold its dimensions in the wet condition?

POM and PEEK absorb minimal moisture and can be machined to ±0.025 mm or better, which reduces the risk of swelling or warping over time²⁷. Nylon-based bearings may need post-machining conditioning after moisture absorption²⁷.

That is the polymer route to dimensional stability in submerged or humid service — the material itself resists the water. The steel route solves the same problem differently.

For moisture and washdown in food processing, marine and outdoor applications, the sources recommend stainless steel bearings or corrosion-resistant coatings with contact seals¹⁹. So the two options fail in different ways: a polymer can swell or creep, while a steel bearing corrodes unless the seal keeps the water out.

Seal choice matters on the steel side. Lip seals degrade by friction and have limited water capability, whereas non-contact labyrinth seals have no friction wear.

Labyrinth seals can be used with water only if the materials are rust-proof and the water level stays below the sealing diameter²⁴. If you keep steel in a wet duty, that seal condition is the one to verify.

The sources give no water-absorption percentages or long-term submerged dimensional data for PEEK, POM or PTFE, so ask the supplier for the polymer side of this comparison.

Do you need an insulator or a conductor — and can the polymer shed its heat?

Plastics are electrical insulators and non-magnetic, while steel is conductive¹⁴. In electrically sensitive equipment such as VFD-controlled motors, a non-conductive bearing material is described as an irreplaceable advantage⁸.

If your application has shaft-current or electromagnetic-sensitivity concerns, that property alone can decide the material class. The same property cuts the other way on heat.

Plastics have inherently lower thermal conductivity than metals and do not dissipate heat efficiently. So high-speed or high-friction use can cause softening, dimensional change or melting; hybrid plastic-with-metal-backing designs are suggested where heat dissipation matters³⁴.

Insulation and heat removal are therefore a trade-off you have to weigh together, not two separate checks. The sources do not publish thermal or electrical conductivity values for PEEK, POM or PTFE, so you cannot compute the heat balance from this evidence.

If the duty is high-speed or the enclosure is unventilated, ask the supplier for the conductivity figure and the surface-temperature limit before you commit to a polymer.

Which of PEEK, POM or PTFE fits once temperature and moisture are known?

The sources differentiate the three polymers on temperature ceiling and moisture uptake, but they give no chemical-compatibility table, so this table narrows the shortlist rather than settling the choice. PTFE carries the highest reported ceiling at 260°C and PEEK at 250°C, both with excellent chemical resistance and low friction²⁰.

POM has no reported ceiling in this source set, so its temperature fit must come from the supplier. On moisture, POM and PEEK are the two the sources describe as absorbing minimal moisture and holding tight tolerances, while nylon may need conditioning after moisture absorption²⁷.

If your duty is both hot and wet, PEEK is the only polymer in this set with both a reported ceiling and reported moisture behaviour. But that is a shortlist result, not a compatibility verdict.

The final compatibility call must come from the supplier. No source here provides chemical-compatibility data for PEEK, POM or PTFE against named chemicals, concentrations or temperatures, so the shortlist above is the furthest the evidence goes.

What to demand from the supplier before you release the RFQ

The evidence does not establish the figures your final specification depends on, so each of these must be a documented supplier deliverable rather than an assumption.

• ✓Chemical-compatibility data for the specific polymer against your named chemicals, concentrations and temperatures.
• ✓Food-contact certification evidence (FDA 21 CFR, EU 10/2011, NSF H1) for the bearing material and any lubricant or additive.
• ✓Static and dynamic load ratings, allowable pressure (P) and velocity (V) limits, and safety factors for the specific PEEK/POM/PTFE bearing.
• ✓Friction coefficient and wear rate for the polymer against your counterface material and surface finish, in dry, lubricated and submerged conditions.
• ✓Water-absorption percentage and long-term submerged dimensional-stability data.
• ✓Continuous-temperature rating for the complete bearing under load, not just the material capability.
• ✓Confirmation that any grease used is free of molybdenum, which is flagged as a product contaminant in food and cleanroom service.

Where the sources disagree on stainless versus polymer

The disagreement is not about whether stainless works — it is about the conditions under which it stops working. One position holds that stainless steel provides excellent resistance to moisture and mild chemicals and is a top choice for food processing and medical equipment, with 440C specifically resisting fresh water and mild chemical environments^16,25.

The other holds that polymers are the right answer where steel would rust and traditional lubrication is prohibited^23,28. Both can be true at once, because they describe different chemical severities.

The sources do not resolve which side applies to your process, so treat this as unresolved and settle it with your own chemical and cleaning data. The load penalty on the stainless side is also worth noting: 440C is reported at about 20% lower load capacity than 52100 chrome steel²⁵.

What the sources do not establish

• Chemical-compatibility data for PEEK, POM and PTFE against named chemicals, concentrations and temperatures, and against stainless or coated steel under the same conditions.
• Food-contact certification evidence (FDA 21 CFR, EU 10/2011, NSF H1) for plastic bearing materials and for any lubricants or additives used with them.
• Static and dynamic load ratings, allowable pressure (P) and velocity (V) limits, and safety factors for PEEK, POM or PTFE bearings.
• Friction coefficients and wear rates for PEEK, POM or PTFE versus steel in dry, lubricated and submerged conditions, including counterface material and surface finish effects.
• Water-absorption percentages and long-term submerged dimensional-stability data for PEEK, POM or PTFE.
• Initial cost, total cost of ownership, replacement frequency and standard-size versus custom-tooling availability for plastic bearings.
• Thermal-expansion coefficients and thermal or electrical conductivity values for PEEK, POM or PTFE to compare against the steel data provided.
• Any source directly addressing PEEK, POM or PTFE rolling bearings, as opposed to cages, plain bushings or housings.