PTFE vs PEEK: Which Material Is More Suitable for Your Application?
In the selection of high-performance engineering plastics, polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK) are the two most common candidate materials. The former is known as the “King of Plastics,” while the latter is hailed as the “King of Engineering Plastics.” The price gap between them can reach 5–10×. A wrong procurement decision can at best increase cost, and at worst cause seal failure or structural fracture. This article compares the two across four dimensions—material properties, performance parameters, application scenarios, and cost-effectiveness—and provides clear selection guidance.
1. Material Property Comparison Table
| Property | PTFE | PEEK |
|---|---|---|
| Density (g/cm³) | 2.13–2.20 | 1.30–1.32 |
| Melting point (°C) | 327 | 343 |
| Glass transition Tg (°C) | — | 143 |
| Continuous service temp (°C) | -200 ~ 260 | -60 ~ 260 (UL RTI 240) |
| Tensile strength (MPa) | 20–35 | 90–100 |
| Tensile modulus (GPa) | 0.4–0.55 | 3.6 |
| Elongation at break (%) | 200–400 | 11–50 |
| Flexural strength (MPa) | Low (flexible) | 170 |
| Coefficient of friction (dry) | 0.05–0.10 | 0.30–0.40 |
| Water absorption (%) | <0.01 | 0.5 |
| Dielectric strength (kV/mm) | 60–100 | ~19 (3mm) |
| Limiting oxygen index LOI (%) | 95 | 35 |
| Flammability rating | Inherently flame-retardant | UL94 V-0 (unfilled) |
| Relative price (USD/kg) | 6–20 | 50–100 |
Data sources: ASTM D638 (tensile), ASTM D790 (flexural), ISO 1183 (density), UL 94 / UL 746B (flammability / RTI).
2. Performance Parameter Comparison
Mechanical: PEEK’s tensile strength is ~3–4× that of PTFE, and its modulus is an order of magnitude higher, enabling metal replacement in load-bearing structural parts, gears, and bearings. PTFE is low in strength and exhibits significant cold flow (creep), so it cannot be used in load-bearing applications, but its high ductility makes it ideal for compression-molded complex seals.
Friction & wear: PTFE has an extremely low friction coefficient (0.05–0.10) and self-lubrication, making it the first choice for dry-friction conditions. PEEK’s dry friction coefficient is higher (0.3–0.4), but when filled with PTFE, graphite, or carbon fiber, friction drops to 0.15–0.2, and wear resistance significantly exceeds that of pure PTFE.
Temperature & chemical: Both have a continuous service temperature ceiling near 260°C. PTFE’s chemical resistance is nearly perfect, attacked only by molten alkali metals and fluorine. PEEK resists most organic solvents, oils, and acids, but is limited under strong protic acids (e.g., hot concentrated sulfuric acid).
Electrical & flame: PTFE offers high dielectric strength and LOI of 95%, making it the top choice for high-frequency / high-voltage insulation. PEEK itself is UL94 V-0 with LOI 35%, giving it an edge in high-temperature flame-retardant structural parts.
3. Application Scenario Analysis
- PTFE suits: Chemical pipe linings, valve seals, gaskets, non-stick coatings, medical catheters, high-frequency cable insulation—prioritize wherever “low friction + strong corrosion resistance + electrical insulation” is needed.
- PEEK suits: Aerospace fasteners, automotive transmission gears, semiconductor wafer carriers, orthopedic implants, downhole oilfield instruments—prioritize wherever “high strength + high temperature + dimensional stability” is needed.
4. Cost-Effectiveness Evaluation
PTFE raw material costs ~1/6–1/10 of PEEK and is easy to mold with low processing energy. However, if the application requires structural strength, compensating for PTFE’s mechanical weakness often means larger cross-sections or switching to metal, so the total cost is not necessarily lower. PEEK has a higher upfront cost but reduces part count, extends service life, and cuts weight—yielding a better TCO (total cost of ownership) in critical components. Rule of thumb: choose PTFE for non-load-bearing seals / insulation; choose PEEK for load-bearing high-temperature structural parts.
5. Selection Advice
- Pure sealing, lining, low-friction sliding parts → Choose PTFE (lowest cost, best corrosion resistance).
- Load-bearing structures, gears, bearings, implants → Choose PEEK (sufficient strength and toughness).
- High temperature + flame retardancy + dimensional stability → Choose PEEK (UL94 V-0, halogen-free).
- High-voltage high-frequency insulation → Choose PTFE (superior dielectric properties).
- Extremely tight budget with mild conditions → Prefer PTFE; if service life is critical, recalculate by TCO.
Conclusion
PTFE and PEEK are complementary rather than substitutable: PTFE wins on “lubrication, corrosion resistance, insulation, low cost,” while PEEK wins on “strength, heat resistance, flame retardancy, dimensional stability.” When procuring, first define the three hard constraints of your application (load-bearing or not, temperature range, media corrosion), then select against the table—this avoids 80% of material selection mistakes.