PEEK vs. PTFE (Teflon): Selecting Between High-Performance and Ultra-Low Friction Polymers
PEEK vs. PTFE: Strength vs. Slip
Polyetheretherketone (PEEK) and Polytetrafluoroethylene (PTFE, commonly known as Teflon) serve fundamentally different roles in engineering, despite both being high-performance fluorinated polymers. PEEK is chosen for its combination of strength, temperature resistance, and chemical resistance. PTFE is chosen for its unmatched coefficient of friction and absolute chemical inertness.
This comparison references ASTM International testing standards and manufacturer data from Victrex (PEEK) and Chemours/Daikin (PTFE).
Friction and Wear
PTFE's coefficient of friction (0.05-0.10 static) is the lowest of any solid material — this is its primary engineering advantage. PEEK's CoF (0.30-0.40) is significantly higher but its wear resistance is 10-100x better. In bearing and seal applications, PTFE alone wears rapidly; carbon/graphite/MoS₂-filled PTFE compounds bridge this gap but never match PEEK's wear life.
- Dynamic CoF: PTFE 0.05-0.10; PEEK 0.30-0.40
- PV limit (unfilled): PTFE ~1,000 psi·fpm; PEEK ~30,000+ psi·fpm
- Wear factor: PTFE 10-100x higher wear rate than PEEK
Chemical Resistance
PTFE is the gold standard — virtually inert to all chemicals except molten alkali metals and fluorine at high temperatures. PEEK resists most chemicals but is attacked by concentrated sulfuric acid, nitric acid, and some halogenated compounds. For applications involving aggressive chemical exposure with no mechanical load, PTFE is the clear choice.
Mechanical Properties
PEEK dramatically outperforms PTFE in every mechanical category:
| Property | PEEK | PTFE |
|---|---|---|
| Tensile Strength (MPa) | 100 | 25-35 |
| Flexural Modulus (GPa) | 3.6 | 0.5-0.7 |
| Creep Resistance | Excellent | Poor (cold flows under load) |
| Hardness (Shore D) | 85 | 55-65 |
PTFE's most significant mechanical weakness is cold flow (creep) — it deforms permanently under sustained load. This makes PTFE unsuitable for structural applications without reinforcement or backup rings.
Recommendations
- Non-lubricated bearings: Carbon-filled PTFE for lowest friction; PEEK for longest wear life
- Chemical process seals: PTFE for aggressive chemicals; PEEK for high-pressure/high-temperature
- Back-up rings: PEEK — PTFE cold flows and cannot provide structural support
- Food contact surfaces: PTFE — FDA-compliant with broad approval; PEEK also compliant but more costly
- Semiconductor wet process: PTFE for pure chemical resistance; PEEK where mechanical loads exist
References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- ISO. ISO 1043 — Plastics — Symbols and Abbreviated Terms. iso.org
- National Institute of Standards and Technology (NIST). Polymer Properties Database. nist.gov
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb — Material Property Data. matweb.com