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Polyether ether ketone (PEEK)

Polyether ether ketone (PEEK)

Polyether ether ketone (PEEK) is a colourless organic polymer thermoplastic in the polyaryletherketone (PAEK) family, used in engineering applications. PEEK (polyetheretherketone) is a semicrystalline, high-temperature (up to 500° F) engineering thermoplastic that is excellent for applications where thermal, chemical, and combustion properties (UL flammability rating of V-0) are critical to performance. At the same time, PEEK emits little smoke or toxic gas when exposed to flame. This material is tough, strong, and rigid and has superior creep resistance. It also resists radiation and a wide range of solvents. With its resistance to hydrolysis, PEEK can withstand boiling water and superheated steam used with autoclave and sterilization equipment at temperatures higher than 482° F. PEEK resins are available in unreinforced, 30% glass-fiber reinforced, 30% carbon-fiber reinforced, and HPV-reinforced grades.

PEEK  is a semi-crystalline thermoplastic with a linear aromatic polymer structure, high performance engineering thermoplastic. The fully recyclable material melts at 343°C and possesses exceptional mechanical properties with resistance to chemicals, wear, fatigue and creep even at high operating temperatures where it is commonly used in service.

PEEK also has low moisture absorption, stable dielectric (insulating) properties and inherently low flammability. The amazing thing about PEEK is the wide range of processing options from injection molding, compression molding, and extrusion into shapes, film or fibers, to thermoforming, spray coating, or stock shape machining – it is truly one of the most versatile structural materials available.

PEEK grades offer chemical and water resistance similar to PPS (PolyPhenylene Sulfide), but can operate at higher temperatures. PEEK can be used continuously to 480°F (250°C) and in hot water or steam without permanent loss in physical properties. For hostile environments, PEEK is a high strength alternative to fluoropolymers. PEEK carries a V-0 flammability rating and exhibits very low smoke and toxic gas emission when exposed to flame. And unfilled PEEK is approved by the FDA for food contact applications (since 1998).

A high performance thermoplastic with the characteristics common to this group - strong, stiff, hard, high temperature resistance, good chemical resistance and inherently low flammability and smoke emission. PEEK is pale amber in colour and usually semi-crystalline and opaque, except thin films are usually amorphous and transparent. It also has very good resistance to wear, dynamic fatigue and radiation, but it is difficult to process and very expensive. Filled grades, including ones designed for bearing-type applications, are also used.

PEEK exhibits excellent resistance to a wide range of organic and inorganic chemicals. The compatibility of PEEK with many chemicals at 200C (680F) has been investigated and the results for unreinforced grades. PEEK is a strong and stiff plastic material that is often used in applications where performance at elevated temperatures is required. PEEK has outstanding chemical resistance as well as resistance to steam and hot water.

Key Properties

  • Continuous service temperature of 500º F
  • Low smoke and toxic-gas emissions
  • Very low moisture absorption
  • Excellent fatigue, stress-crack, hydrolysis and chemical resistance
  • Superior creep resistance


PEEK (Unfilled)

This general purpose grade is unreinforced and offers the highest elongation and toughness of all PEEK grades. Unfilled PEEK is available in sheet and rod forms in  natural (a very light brown or tan)  color  and is also available in  black . Black PEEK is ideal for instrument components where aesthetics are important, as well as for seal components where ductility and inertness are important. All unfilled PEEK grades comply with FDA regulation 21 CFR 177.2415 for repeated food contact. Unfilled PEEK is an unreinforced general-purpose grade that offers steam and wear resistance. It provides the greatest elongation and toughness of all PEEK grades. It is ideal for instrument components where aesthetics is a concern.

PEEK (30% Glass Filled)

The addition of glass fibers significantly reduces the expansion rate and increases the flexural modulus of PEEK. This grade is ideal for structural applications that require improved strength, stiffness, or stability, especially at temperatures above 300°F (150°C). Glass-filled PEEK is  light brown or tan  in color.  

PEEK (30% Carbon Filled)

The addition of carbon fibers enhances the compressive strength and stiffness of PEEK, and dramatically lowers its expansion rate. It offers designers optimum wear resistance and load carrying capability in a PEEK-based product. This grade provides 3½ times higher thermal conductivity than unreinforced PEEK -- dissipating heat from the bearing surface faster. Carbon-filled PEEK is  black in color.  The result is improved bearing life and capability.

PEEK (Bearing Grade, Ketron HPV)

This grade of PEEK, containing carbon fiber reinforced with graphite and PTFE lubricants, offers the lowest coefficient of friction and the best machinability for all PEEK grades. Bearing grade PEEK has an excellent combination of low friction, low wear, high limiting PV, low mating part wear, and easy machining. Bearing grade PEEK is  black or  dark grey in color.


Because of its robustness, PEEK is used to fabricate items used in demanding applications, including bearings, piston parts, pumps, HPLC columns, compressor plate valves, and cable insulation. It is one of the few plastics compatible with ultra-high vacuum applications. PEEK is considered an advanced biomaterial used in medical implants. It is finding increased use in spinal fusion devices and reinforcing rods. It is extensively used in the aerospace, automotive, and chemical process industries. PEEK's mechanical properties at elevated temperatures have led to it being used in at least two varieties of Reprap extruder as thermal insulation. This means the main mechanical structure of the extruder can be made of the same material that is being extruded, provided that the PEEK insulator prevents heat from traveling beyond the intended melt zone. Typical applications include the marine, nuclear, oil-well, electronics, medical. Applications include flexible printed circuit boards (film), fibres and monofilaments, injection moulded engineering components.

Polyether ether ketone (PEEK) Pictures