Overview: A Head-to-Head Comparison of Two Engineering Plastics
Polytetrafluoroethylene (PTFE) and Polyether Ether Ketone (PEEK) are two standout materials in the world of high-performance engineering plastics. Both are renowned for their exceptional chemical resistance, thermal stability, and low friction, yet they differ markedly in molecular structure, mechanical properties, and application suitability. This article provides a systematic comparison across material characteristics, performance parameters, application scenarios, and cost-effectiveness to help procurement professionals make informed decisions.
Material Properties Comparison Table
| Property | PTFE (Polytetrafluoroethylene) | PEEK (Polyether Ether Ketone) |
|---|---|---|
| Trade Name Examples | Teflon® (DuPont/Chemours) | Victrex®, Solvay KetaSpire® |
| Molecular Structure | Semi-crystalline fluoropolymer | Semi-crystalline aromatic polyketone |
| Density (g/cm³) | 2.14–2.20 | 1.30–1.32 |
| Max Continuous Use Temp (°C) | 260 | 250 |
| Short-Term Peak Temp (°C) | 300 | 300+ |
| Melting Point (°C) | 327 | 343 |
| Tensile Strength (MPa) | 20–35 | 90–100 |
| Flexural Modulus (GPa) | 0.5–0.7 | 3.5–4.4 |
| Elongation at Break (%) | 200–400 | 30–50 |
| Coefficient of Friction | 0.05–0.10 (Ultra-Low) | 0.20–0.40 (Low) |
| Volume Resistivity (Ω·cm) | >10¹⁸ | 10¹⁶–10¹⁷ |
| Chemical Resistance | Nearly universal (except molten alkali metals) | Excellent (dissolves in concentrated H₂SO₄) |
| Water Absorption (24h, %) | <0.01 | 0.1–0.5 |
| CTE (×10⁻⁵/K) | 10–12 | 4–5 |
| Flammability (UL94) | V-0 | V-0 |
Deep Dive into Performance Parameters
1. Mechanical Properties — PEEK Dominates
PEEK’s tensile strength (90–100 MPa) is 3–4 times that of PTFE (20–35 MPa), and its flexural modulus is 5–7 times higher. This makes PEEK the clear choice for structural components under mechanical load. PTFE is soft and prone to creep (cold flow) under sustained load, while PEEK exhibits roughly 10× the creep resistance of PTFE, providing significantly better dimensional stability.
2. Friction and Wear — Lowest Friction vs Best Wear Resistance
PTFE has the lowest coefficient of friction among all solid materials (0.05–0.10), making it an ideal lubricating material. However, its wear resistance is poor (wear rate ~10⁻³ mm³/N·m). PEEK has a slightly higher friction coefficient (0.20–0.40) but vastly superior wear resistance (wear rate ~10⁻⁶ mm³/N·m), making it better for long-term wear applications like bearings and seal rings. Carbon-fiber or graphite-filled PEEK composites can further reduce friction and improve wear.
3. Thermal Performance — Comparable
Both materials exhibit similar continuous use temperatures (PTFE 260°C / PEEK 250°C) and can withstand short-term peaks above 300°C. PEEK has a higher melting point (343°C vs 327°C) and a lower coefficient of thermal expansion (4–5 × 10⁻⁵/K vs 10–12 × 10⁻⁵/K), offering better dimensional stability during temperature cycling.
4. Chemical Resistance — PTFE is Nearly “Immune”
PTFE is renowned for its near-total chemical inertness — it resists virtually all chemicals except molten alkali metals and a few fluorinated compounds. PEEK also offers excellent chemical resistance but dissolves in concentrated sulfuric acid (>98%) and can degrade with prolonged exposure to hot strong bases. For extreme chemical environments, PTFE is the safer choice.
5. Electrical Properties — PTFE is the Ultimate Insulator
PTFE has a volume resistivity exceeding 10¹⁸ Ω·cm, making it one of the best organic electrical insulators known, widely used in high-frequency cables and electronic insulation. PEEK also performs well (10¹⁶–10¹⁷ Ω·cm), sufficient for most electrical applications.
Application Scenarios
| Industry | PTFE Applications | PEEK Applications |
|---|---|---|
| Chemical/Petrochemical | Gaskets, linings, pipes, valve components (extreme chemical) | Pump impellers, compressor valves (medium chemical + high stress) |
| Aerospace | Wire/cable insulation, seals | Structural parts, bearing cages, connectors |
| Semiconductor | High-purity chemical lines, seals | Wafer handling fixtures, CMP rings |
| Medical | Vascular grafts (ePTFE), sutures | Implantable orthopedic/spinal devices (ISO 10993) |
| Automotive | Seals, lubricating bushings, cable sheathing | Transmission components, engine peripherals, brakes |
| Food Processing | Non-stick coatings, conveyor belts, seals | High-temp fixtures, inspection equipment parts |
Cost-Benefit Analysis
Price Gap: PEEK costs approximately 10–20× more than PTFE. PTFE is widely available at $10–50/kg, while PEEK — a specialty engineering plastic — ranges from $100–500/kg depending on grade and filler system.
Total Cost of Ownership: Despite the higher upfront cost, PEEK parts can last 5–10× longer than PTFE in high-strength, high-wear, or high-stability applications, reducing maintenance and replacement frequency. In applications requiring only chemical resistance or low friction (e.g., static seals), PTFE’s cost advantage is unbeatable.
Processing Cost: PTFE cannot be injection molded (extremely high melt viscosity) and is typically compression-molded or machined, resulting in lower production efficiency. PEEK can be processed via injection molding, extrusion, and compression molding, making it suitable for high-volume precision manufacturing with decreasing unit costs at scale.
Selection Recommendations
Choose PTFE when:
- Extreme chemical exposure (strong acids/bases/solvents)
- Ultra-low friction is required (plain bearings, guide rails)
- Parts experience minimal mechanical load (static seals, linings)
- Cost sensitivity — material unit price is a key constraint
- Dimensional precision is not critical (PTFE has high CTE, prone to creep)
Choose PEEK when:
- Components must withstand moderate to heavy mechanical loads
- Long-term wear resistance is needed (dynamic seals, bearings, gears)
- Frequent temperature fluctuations demand dimensional stability
- Weight reduction is important (PEEK density is only 60% of PTFE)
- High-volume production via injection molding is planned
- Biocompatibility certification required (medical devices, food contact)
Conclusion
PTFE and PEEK are not simple substitutes — they are complementary materials with distinct strengths. PTFE is irreplaceable in extreme chemical and ultra-low-friction applications, offering cost-effective sealing and lubrication. PEEK, with its superior mechanical strength, wear resistance, and processing versatility, is the ideal choice for structural components, delivering significant lifecycle advantages despite its higher unit cost.
Actionable Advice: Before selecting, clarify the loading conditions (static vs dynamic, stress levels), chemical media type and concentration, operating temperature range, expected service life, and production volume. When possible, conduct small-scale testing to validate material performance under actual operating conditions rather than relying solely on datasheets. Contact us for further technical consultation.