PEEK
Also: polyetheretherketone, PEEK 450G, Victrex PEEK, Ketron PEEK, Tecapeek, KetaSpire, Zeniva (implant grade), PEEK-GF30 (glass-filled), PEEK-CA30 (carbon-filled), PEEK HPV (bearing grade), polyaryletherketone (PAEK)
PEEK is the top-of-the-range machinable thermoplastic: strong to 250 °C, chemically inert, steam-sterilizable and implantable, at a premium price. Values for unfilled stock.
Sourcing PEEK parts or stock?
- Machine shops that work with plastics · 189
- Extrusion companies that work with plastics · 121
- 3D Printing companies that work with plastics · 55
- All U.S. manufacturers working with plastics · 1,204
At a glance
| Density | 1.31 g/cm³ (0.047 lb/in³) |
|---|---|
| Tensile strength | 100 MPa (14.5 ksi) at yield |
| Yield strength | 100 MPa (14.5 ksi) tensile yield |
| Hardness | Rockwell M 99 (Shore D 85-88) |
| Elongation | 20-40% at break (extruded stock); molded 450G up to 45% |
| Modulus of elasticity | 3.7 GPa (0.54 Msi) tensile; about 10-12 GPa (1.5-1.7 Msi) for GF30 and CA30 grades |
| Thermal | Tg 143 °C (289 °F); melts at 343 °C (649 °F); continuous service 250 °C (480 °F); HDT 152 °C (306 °F) unfilled and above 300 °C (570 °F) for 30% glass-filled, at 1.82 MPa |
| Composition | Poly(oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene), unfilled; filled grades add 30% glass fiber, 30% carbon fiber, or PTFE/graphite/carbon bearing packages |
Typical values, Natural (tan) extruded rod and plate, unfilled, annealed, 23 °C (73 °F). Confirm against the mill certificate and the purchase spec.
- MachinabilityGood
- Cuts cleanly with sharp carbide, but the material insulates and heat builds in the tool; flood with water-based coolant, anneal after roughing on tight-tolerance parts. Glass and carbon fillers abrade tools quickly; use PCD or fresh carbide.
- WeldabilityFair
- Cannot be solvent bonded (it resists solvents). Hot-plate, ultrasonic, laser and induction welding all work with the right equipment; adhesives (epoxy) bond after plasma or abrasive surface prep. Mechanical fastening is the usual answer.
- FormabilityPoor
- Thin film and tube can be thermoformed or heat-set above Tg, but sheet and plate are not bent in practice. Parts are machined, molded or extruded to shape.
- Corrosion resistanceExcellent
- Resists acids, bases, hydrocarbons, solvents, steam, hot water and radiation. Attacked by concentrated sulfuric and nitric acid, halogens and some halogenated hydrocarbons at temperature. Moisture absorption is about 0.1%, so it holds size wet.
PEEK (polyetheretherketone) is a semi-crystalline high-performance thermoplastic that keeps useful strength and stiffness to about 250 °C (480 °F), resists nearly every chemical except concentrated sulfuric acid and halogens, survives steam, radiation and hydrolysis, and is available in implantable grades. It is what engineers reach for when a plastic part must live in an engine, a downhole tool, a semiconductor wet bench, a sterilizer or a human body.
Unfilled PEEK is tan, about 100 MPa (14.5 ksi) at yield, with a modulus near 3.7 GPa. Glass-filled (GF30) and carbon-filled (CA30) grades roughly double the stiffness and raise the heat deflection temperature from about 150 °C to over 300 °C; bearing grades add PTFE, graphite and carbon fiber for dry-running wear. Its glass transition at 143 °C (289 °F) matters: above it the unfilled material softens noticeably even though it does not melt until 343 °C (649 °F).
The price is the constraint. PEEK stock costs tens of times what acetal does, and a bar-stock part is often mostly chips, so parts are designed small, machined from near-size rod or tube, and specified only where Ultem, PPS or a filled nylon will not do. Machining PEEK is straightforward but builds heat; annealing between roughing and finishing keeps tight-tolerance parts from moving.
Heat treatment
Annealing (stress relief) only. Producer stock is annealed; re-anneal after roughing at about 200-220 °C (390-430 °F) with a slow rise, hold about 1 hour per 6 mm (1/4") of thickness, and slow cool, then finish machine. Thin extruded sections can be sold amorphous (darker, translucent); a full anneal crystallizes them to the tan, opaque state and slightly shrinks the part.
Tempers and conditions
- Natural (unfilled, tan)
- Black
- Glass-filled 30% (GF30)
- Carbon-filled 30% (CA30)
- Bearing grade (PTFE, graphite and carbon fiber, HPV)
- Medical / implant grade (Zeniva, Invibio PEEK-Optima)
- Electrostatic-dissipative (ESD) grades
Stock forms
- Round rod
- Plate and sheet
- Tube
- Thin film
- Molding pellets
- FDM filament and SLS powder (specialty)
Relative cost
Tier 5 of 5. The most expensive common stock-shape plastic: roughly 20-40x acetal per pound, and about twice Ultem. Filled and medical grades cost more again. Minimize stock size and chips.
Typical applications
- Seals, seats and backup rings in oil and gas tools
- Semiconductor wafer handling and wet-process components
- Aerospace bushings, brackets and wire insulation
- Spinal cages, trauma plates and dental parts (implant grades)
- Surgical instrument handles that go through the autoclave
- Pump impellers, gears and valve components in chemical service
- Electrical insulators and connector bodies at high temperature
Process compatibility
How PEEK takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| CNC Machining | GoodGood | The main way PEEK parts are made in the U.S.; sharp carbide, coolant, and an anneal between rough and finish for tight work. Can PEEK be machined? |
| CNC Milling | GoodGood | Mills well from plate; plan the stock so the part is not mostly chips, because the material is the cost. |
| CNC Turning | GoodGood | Seals, bushings and seats from rod or tube; buy tube to save material on rings. |
| Swiss Machining | GoodGood | Small medical and connector parts from ground rod; implant grades come with material traceability. |
| Injection Molding | GoodGood | Molds at 370-400 °C (700-750 °F) barrel and 150-180 °C (300-360 °F) mold; hardened tooling and a molder set up for it. Justified at volume. |
| FDM 3D Printing | FairFair | Printable on high-temperature machines (400 °C nozzle, heated chamber); crystallinity and strength vary with the printer, so treat printed PEEK as a prototype unless qualified. |
| SLS 3D Printing | FairFair | PEEK/PAEK powder sinters on a few high-temperature SLS systems; rare, expensive, and not a job-shop service. |
| Waterjet Cutting | GoodGood | Profiles plate without heat or tool wear; a good way to rough blanks from expensive sheet. |
| Laser Cutting | PoorPoor | Thin film cuts; plate chars and the heat-affected edge needs machining off. Waterjet or mill instead. |
| Vibratory Finishing | GoodGood | Deburrs machined parts without embedding; use plastic or ceramic media. |
| Bead Blasting | FairFair | Uniform matte texture on cosmetic or bonding surfaces; mask sealing faces. |
| Anodizing | Not recommendedNot recommended | An aluminum process; plastics cannot be anodized. Buy pigmented PEEK for colour. |
| Plating | Not recommendedNot recommended | Not a plating-grade plastic; adhesion needs specialty etching. Specify a conductive (carbon-filled or ESD) grade if the aim is static dissipation. |
Compare PEEK
Design and sourcing tips
- Specify the grade: "PEEK 450G unfilled", "PEEK GF30", "PEEK CA30" or a bearing grade. Filled grades are stiffer and more heat-resistant but anisotropic and abrasive to cut.
- Design to Tg, not Tm: unfilled PEEK softens above 143 °C (289 °F). For loaded parts above that, use a filled grade or check the modulus at temperature on the data sheet.
- Buy near-net stock (tube for rings, rod sized close to the part): material is most of the price, and machining time is modest.
- Ask for annealed stock and, for tolerances under ±0.05 mm (±0.002"), a rough-anneal-finish sequence; PEEK moves as machining stresses relax.
- For implants, specify the implant grade (ASTM F2026) and lot traceability on the PO; industrial PEEK is chemically the same but not certified.
- Consider Ultem (PEI) at about half the price where the service temperature is under 170 °C (340 °F) and no steam or strong alkali is involved.
Frequently asked questions
- What temperature can PEEK withstand?
- Unfilled PEEK is rated for continuous service to about 250 °C (480 °F) and melts at 343 °C (649 °F). Its glass transition at 143 °C (289 °F) is the more useful limit for loaded parts: stiffness drops sharply above it unless the grade is glass- or carbon-filled, which pushes the heat deflection temperature above 300 °C (570 °F).
- Is PEEK stronger than aluminum?
- No. Unfilled PEEK yields at about 100 MPa (14.5 ksi) with a modulus of 3.7 GPa; 6061-T6 aluminum yields at 276 MPa (40 ksi) with 69 GPa. Carbon-filled PEEK reaches about 200 MPa and 20 GPa. PEEK wins on chemical resistance, insulation, weight and wear, not on strength per volume.
- Why is PEEK so expensive?
- The monomers and the high-temperature polymerization are costly, volumes are small next to nylon or polycarbonate, and stock shapes are extruded slowly. Raw rod runs tens of times the price of acetal. It is specified where its temperature, chemical or biocompatibility properties are needed and nothing cheaper qualifies.
- Can PEEK be 3D printed?
- Yes, on FDM printers with a 400 °C (750 °F) hot end and a heated chamber, and on a few high-temperature SLS systems. Printed PEEK is weaker and less consistent than machined or molded stock, and crystallinity depends on the chamber temperature, so it is best treated as a prototype or a qualified part from a specialist.
- PEEK vs Ultem: which should I use?
- Ultem (PEI) is amorphous, transparent amber, rated to about 170 °C (340 °F), solvent-bondable and about half the price. PEEK is semi-crystalline, opaque, rated to 250 °C (480 °F), tougher in fatigue and better in steam and strong bases. Use Ultem for electrical, sterilizable and structural parts under 170 °C; use PEEK above that or in aggressive chemistry.
Processes that commonly use it
Related materials
Where to verify these values
- Victrex PEEK 450G and filled-grade data sheets
- Solvay KetaSpire PEEK and Zeniva implant-grade data
- Ensinger TECAPEEK and Mitsubishi Chemical Advanced Materials Ketron PEEK stock-shape data
- ASTM F2026; ASTM D638 and D790 test methods
