In industrial sealing applications, PTFE (Polytetrafluoroethylene) and PEEK (Polyether Ether Ketone) are the two most frequently compared high-performance engineering plastics. While both have dedicated user bases, engineers and procurement professionals often face a dilemma when making a selection. This article provides a comprehensive and objective comparison across four dimensions: material properties, performance parameters, application scenarios, and cost-effectiveness.
1. Material Property Comparison
| Property |
PTFE (Polytetrafluoroethylene) |
PEEK (Polyether Ether Ketone) |
| Max Continuous Service Temp |
260°C |
250°C (short-term 300°C) |
| Tensile Strength |
20–35 MPa |
90–100 MPa |
| Flexural Modulus |
400–600 MPa |
3,500–4,200 MPa |
| Density |
2.15–2.20 g/cm³ |
1.30–1.32 g/cm³ |
| Coefficient of Thermal Expansion |
12–20 ×10⁻⁶ /°C |
4.5–5.0 ×10⁻⁶ /°C |
| Chemical Resistance |
Near-universal chemical resistance |
Good against most chemicals; attacked by conc. H₂SO₄/HNO₃ |
| Wear Resistance |
Poor; requires filler modification |
Excellent; self-lubricating |
| Radiation Resistance |
Poor (prone to degradation) |
Good (γ-ray resistant) |
| Processability |
Sintering molding; difficult precision machining |
Injection/extrusion molding; easy precision forming |
| Cost (reference) |
Lower (~$15–25/kg) |
High (~$50–100/kg) |
2. Performance Parameter Analysis
2.1 Temperature Resistance
The temperature resistance of both materials is similar. PTFE remains stable below 260°C and maintains flexibility at cryogenic temperatures down to -200°C. PEEK retains higher mechanical strength at elevated temperatures, with short-term resistance up to 300°C. In high-temperature, high-pressure valve sealing applications, PEEK often has the edge.
2.2 Mechanical Properties
PEEK’s tensile strength is 3–4× that of PTFE, and its flexural modulus is nearly an order of magnitude higher. This means PEEK seals deform less and last longer under high-pressure (>10 MPa) conditions. PTFE’s softer texture makes it better suited for low-pressure, low-stress flange gaskets and stuffing box seals.
2.3 Chemical Resistance
PTFE offers near-“universal” chemical resistance — even aqua regia cannot corrode it. PEEK resists most acids, alkalis, and organic solvents, but concentrated sulfuric acid, nitric acid, and certain halogenated hydrocarbons can attack it. For strongly corrosive media, PTFE remains the preferred choice.
2.4 Wear and Sealing Performance
Pure PTFE has poor wear resistance and is prone to cold flow and creep — typically requiring fillers such as carbon fiber, glass fiber, or bronze powder. PEEK inherently offers excellent wear resistance and self-lubricating properties, resulting in significantly longer service life in dynamic sealing applications such as oil seals and shaft seals.
3. Application Scenario Analysis
PTFE – Ideal For
- Strongly corrosive media: Chemical process pumps, reactor vessels, tank seals
- Food/Pharmaceutical: FDA/USDA-compliant low-friction linings and seals
- Cryogenic environments: LNG, deep-cold equipment
- Low-pressure static sealing: Flange faces, pipe joints, sight glass seals
PEEK – Ideal For
- High-pressure dynamic sealing: Hydraulic systems, valve stem seals, oilfield drilling
- High-temperature and high-pressure: Aerospace engines, gas turbine auxiliaries
- High wear requirements: Pump shaft sleeves, slide bearings, valve seat seals
- Radiation environments: Nuclear power plants, nuclear medical equipment seals
4. Cost-Benefit Assessment
By unit price, PTFE material cost is approximately 1/4 to 1/5 that of PEEK. However, selection should not be based on material cost alone:
- Processing cost: PTFE sintering is complex with low yield rates; PEEK injection molding is efficient with high dimensional precision
- Service life: PEEK seals last 3–5× longer under high-pressure dynamic conditions
- Maintenance cost: PEEK’s durability means fewer shutdowns for maintenance
- Overall TCO: For high-pressure, dynamic, and long-cycle operations, PEEK often delivers better cost-effectiveness
5. Selection Recommendations
Choose PTFE: Limited budget, primarily static sealing, strongly corrosive media, wide temperature range (especially cryogenic), FDA certification required.
Choose PEEK: High pressure (>10 MPa), dynamic sealing, high-temperature/high-pressure cycling, long service life and low maintenance priority, tight dimensional control needed.
Hybrid Approach: In complex operating conditions, consider modified PTFE (e.g., carbon-fiber-filled PTFE) or layered PTFE/PEEK sealing structures to combine the advantages of both materials.
Conclusion
There is no universally “best material” — only the material best suited for a specific application. Before final procurement, we recommend consulting with material suppliers or technical teams regarding your operating parameters (temperature, pressure, medium, and rotational speed). Sample testing is advisable when feasible.
Data sources: ASTM D4894 (PTFE), ASTM D4065 (PEEK), ISO 5834, manufacturer technical white papers. Data represents typical commercial grades; refer to supplier test reports for specific grades.