PTFE, Nylon and PEEK form the backbone of engineering plastics in mechanical design. Each one solves a different set of problems, but the boundaries between them aren't always obvious — and engineers regularly over-specify (paying PEEK prices for a job Nylon could do) or under-specify (using Nylon where PTFE's low friction or PEEK's heat tolerance are essential). This guide is a practical, application-driven comparison written for the engineer choosing material for the next bushing, seal, gear or insulator on the bench.
The three materials at a glance
| Property | PTFE | Nylon (PA6 / PA66) | PEEK |
|---|---|---|---|
| Continuous service temp | 260°C | 80–120°C | 250°C (peaks 300°C) |
| Coefficient of friction | Very low (0.05–0.10) | Moderate (0.20–0.30) | Low (0.30, drops with fillers) |
| Tensile strength | Low–moderate | High | Very high |
| Wear resistance (unfilled) | Moderate | Good | Excellent |
| Chemical resistance | Outstanding | Moderate | Excellent |
| Moisture absorption | ≈ 0 % | Up to 8 % | ≈ 0.15 % |
| Machinability | Easy (soft) | Easy | Moderate (hard) |
| Relative cost | ★★ | ★ | ★★★★ |
PTFE — when low friction and chemical inertness rule
PTFE (polytetrafluoroethylene) is the material of choice when something must slide easily, resist almost any chemical, and stay stable across enormous temperature swings.
Where PTFE wins
- Sliding seals and lip seals — friction so low that mating parts often see no measurable wear.
- Chemical-handling components — gaskets, valve seats, lined pipework. PTFE is inert to almost every industrial chemical, including aggressive acids and most solvents.
- Cryogenic to high-temperature service — −200°C to +260°C is routine.
- Non-stick surfaces — release components on moulds, food-contact surfaces.
Where PTFE struggles
Pure PTFE has poor mechanical strength under load and "creeps" under sustained pressure. Filled grades — glass-, carbon-, bronze- or graphite-filled — improve creep resistance dramatically and should be used for any structural or load-bearing PTFE component.
Nylon — the workhorse mid-range
Nylon (polyamide) is the engineer's default when you need a tough, machinable, affordable plastic that will run for years in moderate conditions. The two dominant forms are extruded Nylon (PA6) and the harder, more precise cast Nylon (PA6 cast / MC nylon).
Where Nylon wins
- Gears, sprockets, sliders — high tensile and impact strength, low cost, easily machined.
- Bushings and rollers in dry or moderately lubricated environments.
- Wear pads and chain guides on packaging and conveyor lines.
- Structural mechanical parts at temperatures below 100°C.
Where Nylon struggles
The big weakness is moisture absorption. Standard Nylon picks up several percent water by weight, and this changes both dimensions and mechanical properties. In humid environments, dimensional drift can be 0.5 % or more — significant for a precision part. Cast Nylon is more stable, and oil-filled grades reduce the issue further. For temperatures above 100°C or aggressive chemicals, Nylon is out of its depth.
PEEK — when nothing else will do
PEEK (polyetheretherketone) is the high-performance plastic specifiers reach for when temperature, mechanical load and chemical exposure all demand the best. It is also the most expensive — typically 5–10× the cost of Nylon — so it should be specified deliberately, not by default.
Where PEEK wins
- High-temperature bearings and seals — continuous 250°C with mechanical load.
- Aerospace and oil-and-gas components — chemical resistance under pressure and heat.
- Medical implants and instruments — bio-compatible, sterilisable, dimensionally stable.
- Semiconductor wafer handling — outgassing low enough for high-vacuum environments.
Where PEEK is the wrong call
If your part runs below 100°C, isn't exposed to aggressive chemicals, and isn't load-critical, PEEK is over-specification. A Nylon part will do the job for a fraction of the cost and machine faster.
The 3-question selector
1. Is the operating temperature above 120°C? If yes → eliminate Nylon. If above 200°C → PEEK or filled PTFE only.
2. Is friction or chemical exposure the dominant requirement? If yes → PTFE (filled if loaded).
3. Is the part load-bearing in normal industrial conditions? If yes and answers above were "no" → Nylon.
Filled grades — where the real magic is
Most production engineering plastic parts aren't unfilled material. Common filled grades include:
- Glass-filled PTFE (15–25 % GF) — much higher creep resistance, similar low friction. Standard for valve seats and sliding seals under load.
- Carbon-filled PTFE — adds strength and reduces wear; used in dynamic seals and pump components.
- Oil-filled Nylon — self-lubricating, ideal for bushings and wear pads where lubrication is impractical.
- Glass / carbon-filled PEEK — adds stiffness for high-load mechanical applications; carbon-filled grades are notably stronger and less prone to creep.
Machinability and form availability
All three materials are routinely available in:
- Sheet (typical 1 mm – 100 mm thick)
- Rod (typical 5 mm – 300 mm diameter)
- Tube (extruded or machined)
Nylon and PTFE are easy to machine on conventional equipment. PEEK is harder, generates heat, and benefits from sharp carbide tooling and good chip evacuation. Cast Nylon offers tighter tolerances and lower stress than extruded; for precision parts it's worth the small premium.
Cost-aware specification
A practical hierarchy when designing a new part:
- Start with Nylon. If it can do the job, use it.
- If you need low friction or chemical inertness, move to PTFE — and prefer a filled grade if loaded.
- If temperature or mechanical performance pushes past PTFE's limits, move to PEEK, ideally a filled grade.
Nine out of ten engineering parts can be made from Nylon or filled PTFE. Reserve PEEK for the one in ten where it earns its cost.
Bottom line
PTFE, Nylon and PEEK aren't competitors so much as a tiered toolkit — each one designed for a different envelope of temperature, load, friction and chemistry. Match the material to the operating envelope first, and the cost and supply considerations second, and you'll specify confidently every time.
If you'd like a recommendation for a specific component, send us your drawing and operating conditions — we'll quote material, form and lead time, and ship from ready stock where possible.