PEEK vs Polyimide: Which High-Performance Plastic Wins?

Which Material Should You Choose?Choose PEEK (Polyetheretherketone) if:High-volume injection-molded partscomplex geometriesapplications requiring melt recyclabilityChoose Polyimide PI (Vespel) if:Extreme-temperature wear and friction applications...

PEEK and Vespel polyimide (PI) represent the two highest-performance polymer families capable of continuous service above 250°C, but they achieve this through fundamentally different chemistry — PEEK is a melt-processable semicrystalline thermoplastic, while Vespel PI is a sintered thermoset that cannot be re-melted. This single distinction drives every aspect of the comparison: processability, cost, geometry complexity, recyclability, and application fit.

Property Comparison

Continuous Service Temperature: PEEK: 260°C / Vespel SP-1: 300°C (315°C for SP-21 graphite-filled). Vespel wins by 40-55°C — the critical margin for semiconductor and aerospace applications operating at 280-300°C continuous. Tensile Strength: PEEK: 100 MPa / Vespel SP-1: 86 MPa. PEEK is 16% stronger at room temperature, but Vespel retains a higher percentage of its strength at 260°C+ where PEEK's modulus declines. Friction & Wear: Vespel SP-21 (graphite-filled) has a coefficient of friction of 0.06-0.12 — comparable to PTFE — with wear resistance 10× better than unfilled PEEK. PEEK bearing-grade (450FC30) achieves 0.10 friction but with lower PV limit than Vespel. Creep Resistance: Vespel's thermoset crosslinked structure has zero creep under sustained load at any temperature. PEEK creeps measurably above Tg (143°C) under sustained load — a limitation for long-term static load applications above 200°C. Processability: PEEK is injection-moldable into complex net-shape geometries (gears, brackets, impellers) at high volume. Vespel is sintered from pressed powder — limited to simple geometries (rings, bushings, washers) and requires machining for complex features. Recyclability: PEEK is fully melt-recyclable (20-30% regrind acceptable). Vespel is a thermoset — cannot be re-melted; scrap is landfill or ground filler. Cost: PEEK: $80-200/kg / Vespel: $400-1200/kg. Vespel is 5-10× more expensive, driven by low-volume sintered processing and DuPont's sole-supplier position.

Decision Matrix

Choose PEEK When: (1) The part geometry is complex and requires injection molding — Vespel cannot achieve net-shape for gears, brackets, or impellers; (2) Production volume is high (>1000 parts/year) where injection molding economics dominate; (3) The continuous service temperature is at or below 260°C — PEEK's ceiling; (4) Melt recyclability and regrind use matter for cost control; (5) The application is a medical implant (PEEK-OPTIMA is FDA-cleared; Vespel is not cleared for long-term implant). Choose Vespel When: (1) Continuous service above 260°C is required — semiconductor wafer handling at 280-300°C, jet engine components; (2) Zero creep under sustained load at elevated temperature is critical — Vespel's thermoset structure does not cold-flow; (3) Extreme wear and friction performance is needed — Vespel SP-21 outperforms PEEK bearing-grade in unlubricated sliding; (4) The part geometry is simple (rings, bushings, washers) where sintering is viable; (5) Vacuum and cryogenic applications where Vespel's low outgassing and dimensional stability across extreme temperature swings excel.

Comparison at a Glance

Equivalents & Cross-References

Related Diagnostics & Materials

References & Industry Standards

• ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
• UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
• MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
• ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org