PEK Polyetherketone: Higher-Temperature Alternative to PEEK for Demanding Thermal Environments
Published: 2026-05-29
Polyetherketone (PEK) is a member of the polyaryletherketone (PAEK) family with a higher ketone-to-ether ratio than PEEK, giving it a higher melting point (373°C vs 343°C for PEEK) and superior thermal stability at the upper end of the processing...
Polyetherketone (PEK) is a member of the polyaryletherketone (PAEK) family with a higher ketone-to-ether ratio than PEEK, giving it a higher melting point (373°C vs 343°C for PEEK) and superior thermal stability at the upper end of the processing window. The ketone group (-CO-) is more rigid and thermally stable than the ether group (-O-), so increasing the ketone/ether ratio raises the polymer's melting point and glass transition temperature. PEK's Tg of approximately 155-160°C (versus PEEK's 143°C) provides marginally better property retention in the 150-180°C range.
In practice, PEK is specified over PEEK when the application involves sustained exposure to temperatures in the 260-300°C range, or when the manufacturing process subjects the polymer to brief thermal excursions above PEEK's melting point (343°C). Examples include semiconductor wafer processing components exposed to rapid thermal annealing (RTA) cycles, aerospace engine nacelle components near the hot section, and oil & gas downhole tool components in high-pressure/high-temperature (HPHT) wells exceeding 200°C and 30,000 psi. PEK processes at melt temperatures of 380-410°C with mold temperatures of 180-220°C—requiring machines with enhanced high-temperature capability (ceramic heater bands, oil-heated molds rated to 220°C+, and screws/barrels with high-temperature metallurgy).
Technical Properties
| Density | 1.30 g/cm³ |
|---|---|
| Tensile Strength | 110 MPa |
| Melting Point | 373 °C |
| Shrinkage Rate | 1.0-1.3% |
| Flexural Modulus | 4.0 GPa |
| Hdt | 170 °C at 1.82 MPa |
| Continuous Service Temp | 260 °C |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Victrex PEK | |
| KetaSpire KT-880 | |
| Vestakeep PEK |
Frequently Asked Questions
What is the practical benefit of PEK's higher melting point versus PEEK?
PEK's 30°C higher melting point (373°C vs 343°C) provides two practical benefits: (1) In sustained high-temperature service, PEK retains a higher fraction of its room-temperature mechanical properties at 250-280°C. While both materials are rated for 260°C continuous, PEK's tensile strength at 280°C is approximately 25% higher than PEEK's. (2) PEK tolerates short-term thermal excursions (e.g., 350°C for seconds during a semiconductor RTA step) without melting or gross deformation—PEEK at 350°C is fully molten. The tradeoff is processing difficulty: PEK's higher processing temperature narrows the available machine pool and reduces heater band and thermocouple service life.
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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