Introduction
In high-end engineering plastic selection, polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK) are frequently compared by procurement teams. Both are semi-crystalline specialty plastics, yet they occupy very different positions: PTFE is known for “non-stick, chemical resistance, low friction” and is a highly cost-effective general-purpose fluoropolymer; PEEK stands on “high strength, high temperature resistance, metal replacement” and is the pinnacle high-performance thermoplastic. This article provides a systematic comparison across material properties, performance parameters, application scenarios, and cost-benefit, with clear selection recommendations.
1. Material Properties Comparison
| Property | PTFE | PEEK |
|---|---|---|
| Chemical class | Fluoropolymer (C-F bond) | Aromatic crystalline thermoplastic |
| Appearance | Milky white, translucent | Beige/amber, opaque |
| Crystallinity | High (~50–60%) | Medium-high (~30–35%) |
| Processing | Compression/sintering, extrusion (not melt-injectable) | Injection molding, extrusion, machining |
| Flammability | V-0 (inherent) | V-0 (UL94) |
| Food/medical grade | Yes (FDA) | Yes (FDA, ISO 10993) |
2. Performance Parameters
| Parameter | PTFE | PEEK | Test Standard |
|---|---|---|---|
| Density (g/cm³) | 2.13–2.20 | 1.30–1.32 | ASTM D792 |
| Melting point (°C) | 327 | 343 | DSC |
| Continuous service temp (°C) | 260 | 250 | — |
| Tensile strength (MPa) | 20–35 | 90–100 | ASTM D638 |
| Flexural modulus (GPa) | 0.4–0.6 | 3.6–4.1 | ASTM D790 |
| Elongation at break (%) | 200–400 | 30–50 | ASTM D638 |
| Coefficient of friction | 0.04–0.10 | 0.30–0.40 | ASTM D1894 |
| Wear rate | Low (creep in pure form) | Very low (GF/CF reinforced) | ASTM D3702 |
| Dielectric constant (1MHz) | 2.1 | 3.2 | ASTM D150 |
| Water absorption (%) | <0.01 | 0.1–0.5 | ASTM D570 |
| Heat deflection temp HDT (°C) | — | 152 (unreinforced) | ASTM D648 |
Key insights:
- Strength gap: PEEK tensile strength is 3–4× that of PTFE; flexural modulus is nearly 7× higher — a true “structural grade” plastic.
- Friction: PTFE has extremely low static/dynamic friction, a natural self-lubricating material; but pure PTFE suffers “cold flow” (high creep) and requires fillers (glass fiber, bronze). PEEK has higher friction but superior wear resistance (especially reinforced), suited to high-load sliding parts.
- Temperature: Both have similar continuous service temps (250–260°C); PTFE has slightly lower melting point but higher thermal stability ceiling (>400°C decomposition); PEEK withstands 300°C short-term.
3. Chemical Resistance
PTFE, the “King of Plastics,” resists nearly all chemicals (only attacked by molten alkali metals, fluorine, and hot hydrogen fluoride), tolerating strong acids/bases and organic solvents. PEEK also has excellent chemical resistance against most acids, bases, hydrocarbons, and organic solvents, but is affected by strong oxidizing acids (conc. sulfuric/nitric) at high temperature. Extreme corrosion → PTFE; general chemical → either works.
4. Application Scenarios
PTFE: chemical lining, valve seals, reactor liners; non-stick coatings; high-frequency cable insulation, PCB substrates; low-load seals, bearings, gaskets; medical tubing (bio-inert).
PEEK: aerospace brackets, fasteners, interior parts (metal replacement, weight saving); spinal fusion cages, orthopedic implants; semiconductor wafer carriers, CMP rings; automotive transmission bearings, seals, turbo hoses; oil & gas downhole tools, HPHT seals.
5. Cost-Benefit
- Raw material: PTFE general grade ~$7–11/kg, modified $15–30/kg; PEEK ~$70–140/kg, 8–15× PTFE.
- Processing: PTFE requires sintering (higher mold/energy cost, mature process); PEEK injection moldable (complex precision parts) but high processing temp (>380°C), demanding equipment.
- Lifecycle: PEEK’s high unit price is offset by strength, longevity, and metal-replacement weight savings in high-value aerospace/medical; PTFE wins on low cost in high-volume lining/sealing/insulation.
6. Selection Recommendations
Choose PTFE when:
- Extremely low friction / self-lubrication / non-stick is needed
- Extreme chemical corrosion environment
- Wide temperature range (−200 to +260°C) with cost sensitivity
- High-volume low-cost seals / linings / insulation
Choose PEEK when:
- High-strength, high-rigidity structural parts (metal replacement)
- High-temp + high-load + fatigue-resistant sliding/sealing parts
- Medical implant or food-contact high-reliability scenario
- Semiconductor high-purity, low-outgassing requirement
Conclusion
There is no “better” material, only a “more suitable” one. Cost-sensitive, corrosion-resistant, low-friction → PTFE; performance limit, structural load, long life → PEEK. Procurement teams should define operating conditions (temperature, load, media, life) first, then consult the table, and request third-party test reports (ASTM/ISO) to verify key parameters, avoiding batch quality risks from misjudged specs.
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