PEEK vs PI vs PTFE: Choosing a High-Performance Polymer

PEEK, polyimide (PI) and PTFE overlap in temperature and chemistry, but they fail in different ways. The right choice usually comes down to which single property dominates your application.

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Side-by-side

Comparison

Property	PEEK	PI (Vespel-type)	PTFE
Max service temp.	260 °C	300+ °C	260 °C
Friction	Low	Low	Very low
Chemical resistance	Excellent	Good	Near-universal
Stiffness / strength	High	Highest	Low (cold flow)
Wear resistance	Excellent	Excellent	Poor
Relative cost	High	Very high	Medium

Decision guide

How to decide

Choose PEEK for a balance of strength, temperature and wear - the default for structural parts in semiconductor, medical and analytical equipment.
Choose PI when the application runs hotter than PEEK allows and strength must be retained.
Choose PTFE when chemical inertness or the lowest possible friction dominates, and mechanical load is light.
Where cold flow rules out PTFE, PEEK usually takes its place.

FAQ

Frequently asked questions

Which is best for wear?

PEEK and PI both wear well; PTFE does not. For sliding and bearing duty, PEEK with a bearing grade is usually the pragmatic answer.

Which is best for chemical resistance?

PTFE is essentially inert against almost everything; PEEK is excellent against most chemicals but not all; PI is good but the least resistant of the three.

Why does PI cost so much?

Polyimide is difficult to synthesise and machine, and it is usually chosen only when its temperature ceiling is genuinely required.

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