PEK
A PAEK polymer with a higher ether-to-ketone ratio than PEEK, giving higher crystallinity, higher melting point and greater stiffness at elevated temperature; used where PEEK's thermal margin is insufficient.
Reference datasheet — PEK is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
PEK grades and fills
PEK is supplied in 3 conditions, soft to hard.
Compare all 3 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Bearing grade | Pick for unlubricated bushings, seals, thrust washers and bearing cages running hot and dry. | 130 | 2 | ||
30 % short glass fiber reinforced | Choose for stiff, creep-resistant structural parts at 200–260 °C where electrical insulation must be preserved. | 168 | 2.5 | 102 HRM | |
30 % short carbon fiber reinforced | Highest stiffness/strength and lowest CTE with improved thermal conductivity and static dissipation — for metal-replacement structural and semiconductor parts. | 220 | 1.8 | 105 HRM |
Supply forms, finishes and certifications
Ways PEK is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
PWD | Powder grade | Supply form |
NATDefault | Unfilled / Natural | Standard supply |
What is PEK?
A PAEK polymer with a higher ether-to-ketone ratio than PEEK, giving higher crystallinity, higher melting point and greater stiffness at elevated temperature; used where PEEK's thermal margin is insufficient. PEK has a density of 1.3 g/cm³ (0.047 lb/in³), heavier than 69% of polymer grades. Its glass-transition temperature is 157°C (315 °F). PEK has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 110 MPa (16 ksi) — stronger than 97% of polymer grades. Elongation at break is 25% and the elastic modulus is 4 GPa (0.58 Msi).
What is PEK used for?
- aerospace insulation
- high-temp bearings
- downhole tooling components
- high-performance electrical connectors
Advantages
- High strength — 105 MPa (15.2 ksi), better than 97% of polymer grades
- High service temperature — 260°C (500 °F), better than 97% of polymer grades
- Stiff — 4 GPa (0.58 Msi), better than 86% of polymer grades
- Good corrosion resistance — 90/100, better than 82% of polymer grades
- Tough — resists crack growth — 3.5 MPa·√m (3.19 ksi·√in), better than 81% of polymer grades
Limitations
- High embodied carbon — 22 kg CO₂/kg, worse than 100% of polymer grades
PEK properties
Typical room-temperature values; bars are the position among polymer grades.
Physical5
PEK has a density of 1.3 g/cm³ (0.047 lb/in³), heavier than 69% of polymer grades. Its glass-transition temperature is 157°C (315 °F).
Mechanical15
PEK has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 110 MPa (16 ksi) — stronger than 97% of polymer grades. Elongation at break is 25% and the elastic modulus is 4 GPa (0.58 Msi).
Thermal11
PEK is rated for continuous service to 260°C (500 °F). It conducts heat at 0.25 W/m·K (0.144 BTU/hr·ft·°F), better than 72% of polymer grades. Thermal expansion is 45 µm/m·K (25 µin/in·°F).
Electrical7
PEK is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 82% of polymer grades. UV resistance is fair.
Sustainability3
Producing a kilogram of PEK takes about 320 MJ of energy and emits 22 kg of CO₂ — more than 98% of polymer grades. Typical recycled content is 0%.
Manufacturability8
PEK's machinability is good (65/100, better than 66% of polymer grades); weldability good (55/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. PEK is highlighted; hover a dot for its name, or open the interactive family chart.
Working with PEK
Is PEK easy to machine?
Machines like PEEK but harder: sharp polycrystalline-diamond or carbide tooling, high speed with light feed, generous air/mist cooling, and stress-relief anneal near 200 °C before finishing to avoid post-machining distortion.
Can PEK be welded?
No solvent bonding; join by hot-plate, infrared, ultrasonic, laser transmission or induction welding at PAEK temperatures, or use high-temperature epoxy/polyimide adhesive after plasma or abrasive surface activation.
Can PEK be formed, bent or molded?
Inject or extrude at 390–415 °C melt with 180–220 °C tool temperature; dry pellets 3 h at 150 °C, use all-hardened high-temperature barrels and hot runners, and hold tool hot to develop full crystallinity (or anneal 200–250 °C for as-moulded amorphous skins).
PEK chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance.
| Element | Spec limit (wt %) |
|---|---|
| glass fiberGF30 variant only | ≈ 30 |
| carbon fiberCF30 variant only | ≈ 30 |
| PTFE + graphitebearing-grade lubricant package (with ~10 % carbon fiber) | ≈ 20 |
| poly(oxy-1,4-phenylene-carbonyl-1,4-phen1:1 ether:ketone backbone, CAS 27380-27-4; higher ketone content than PEEK | balance |
What surface finishes work on PEK?
Takes fine machining and lapping to low Ra; can be laser marked and plasma-treated for printing or metallization, but is not paintable without primer and yellows in sunlight unless carbon-black pigmented.
How much does PEK cost?
PEK is a high-cost polymer ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
PEK — frequently asked
What is PEK used for?
PEK is typically used for aerospace insulation, high-temp bearings, downhole tooling components and high-performance electrical connectors. In short: higher temperature than PEEK; 260 °C continuous service; stiff at elevated temperature.
What is the yield strength of PEK?
PEK has a typical yield strength of 105 MPa (15.2 ksi) and a tensile strength of 110 MPa (16 ksi) — stronger than 97% of polymer grades. Strength varies by condition: see the 3 listed tempers.
Is PEK easy to machine?
Reasonably — machinability is rated good (65/100, better than 66% of polymer grades). Machines like PEEK but harder: sharp polycrystalline-diamond or carbide tooling, high speed with light feed, generous air/mist cooling, and stress-relief anneal near 200 °C before finishing to avoid post-machining distortion.
Can PEK be welded?
Yes — weldability is rated good (55/100). No solvent bonding; join by hot-plate, infrared, ultrasonic, laser transmission or induction welding at PAEK temperatures, or use high-temperature epoxy/polyimide adhesive after plasma or abrasive surface activation.
What surface finishes work on PEK?
Takes fine machining and lapping to low Ra; can be laser marked and plasma-treated for printing or metallization, but is not paintable without primer and yellows in sunlight unless carbon-black pigmented.
Can PEK be formed, bent or molded?
Inject or extrude at 390–415 °C melt with 180–220 °C tool temperature; dry pellets 3 h at 150 °C, use all-hardened high-temperature barrels and hot runners, and hold tool hot to develop full crystallinity (or anneal 200–250 °C for as-moulded amorphous skins).
What is the maximum service temperature of PEK?
PEK is rated for continuous use to about 260°C (500 °F), and briefly to 320°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does PEK cost?
PEK is a high-cost polymer ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- Victrex HT (PEK) grade data and processing guide — Victrex plc (2022)
- PAEK/PEK semi-finished stock shape properties — Ensinger (2023)
- Poly(aryl ether ketone)s — properties and processing — Hanser / Plastics Handbook (2019)
- CAMPUS / UL Prospector high-temperature thermoplastics datasets — CAMPUS Plastics (2024)
- ISO 527 / ISO 178 / ISO 75 test methods for plastics — ISO (2019)
- PEEK/PAEK (2026)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.