PTFE has the lowest friction of any solid material and resists almost every chemical. It also creeps under sustained load, which is why it is used as a liner, a cage or a low-load bearing rather than a structural one.
| Designations | PTFE · Teflon · polytetrafluoroethylene · filled grades: PTFE+bronze, +carbon, +glass |
|---|---|
| Density | 2.16 g/cm³ (2.2–3.0 filled) |
| Max service temperature | 260 °C continuous · 300 °C short-term |
| Friction | 0.04–0.10 — the lowest of any solid |
| Chemical resistance | Inert to almost everything except molten alkali metals and elemental fluorine |
| Load capacity | Very low unfilled; moderate with bronze filler |
| Wear resistance | Poor unfilled; good with fillers |
| Relative cost | 4× steel |
PTFE's carbon-fluorine bonds are the reason for both its properties: chemically inert because the bond is strong and the molecule is fully shielded, and low-friction because the surface energy is exceptionally low. Nothing sticks to it, including the counterface — which is exactly what a dry bearing wants.
The same weak intermolecular forces explain the weakness. Under sustained load the chains slide past each other and the material creeps. An unfilled PTFE bearing under a steady radial load will flatten over months. That is why real PTFE bearings are either filled (bronze, carbon, glass) or used as a thin liner bonded to a steel backing.
Say which grade: unfilled PTFE for chemical inertness and lowest friction, bronze-filled for load and wear, carbon-filled for creep resistance and conductivity, glass-filled for wear at the cost of chemical resistance. Give the load and the speed, because the PV limit of unfilled PTFE is very low and the difference between a working and a failing design is often a factor of two.
| Property | PTFE (unfilled) | PTFE + bronze | PEEK | Cast bronze |
|---|---|---|---|---|
| Friction | 0.04–0.10 | 0.10–0.20 | 0.15–0.35 | 0.08–0.15 (lubricated) |
| Max temp | 260 °C | 260 °C | 250 °C | 250 °C |
| Load capacity | Very low | Moderate | Moderate | High |
| Creep resistance | Poor | Good | Good | Excellent |
| Chemical resistance | Exceptional | Good | Excellent | Good |
| Relative cost | 4× | 5× | 5–8× | 2× |
The classic application: a woven PTFE liner in a steel race.
Read →Low-load bushings in aggressive fluids.
Read →PTFE and MoS2 transfer films as a lubrication strategy.
Read →When the bearing must carry load at temperature.
Read →Only at very low load. Unfilled PTFE creeps under sustained load and wears quickly in dynamic duty. Filled grades, or a PTFE liner bonded to a steel backing, are what make it a bearing material.
260 °C continuous, 300 °C short-term. Above that it decomposes and releases corrosive fluorides, which is a health and corrosion issue, not just a performance one.
Because it puts the low-friction, chemically inert material exactly where the sliding happens while a steel backing carries the load — solving the creep problem structurally.
Yes, PTFE is widely accepted for food contact, and it is steam-cleanable. Confirm the specific grade and any filler with the supplier, since bronze-filled grades are not food-contact materials.
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