PEEK, short for polyetheretherketone, is a semi-crystalline thermoplastic in the broader polyaryletherketone (PAEK) family, with a melting point near 341°C and a continuous service ceiling of 250-260°C [S3].
Commercial PEEK is sold in four principal variants (unfilled, 30% glass-filled, 30% carbon-filled, and bearing-grade), each aligned to a Mil-P-46183 Type/Class designation, and is offered in rod, plate, tube, and film forms by stockists such as Boedeker, Ensinger, Drake Plastics, and Mitsubishi Chemical Advanced Materials [S2][S3][S4].
PAEK Family Tree: Where PEEK Sits
The PAEK family links phenylene rings through oxygen bridges and carbonyl groups; varying the ether-to-ketone ratio produces PEK, PEEKK, PEKEKK, PEKK, and PEEK, with PEEK being the most commercially dominant composition [S1].
PEKK (polyetherketoneketone) carries a higher ketone content, which raises glass-transition temperature and slows crystallisation, making it a frequent choice in additive manufacturing of dental prosthetics and aerospace brackets [S1]. Within the wider engineering-plastics pyramid, PEEK is grouped with the uppermost high-performance polymers, well above standard plastics and engineering plastics such as PMMA or PA66 on both thermal ceiling and chemical resistance [S1]. For a broader map of where PAEK fits against other super-polymers, see the engineering plastics selection guide.
The Four Core Commercial Grades
Unfilled virgin PEEK (Mil-P-46183 Type I) offers the highest elongation and toughness of any grade, with a tensile strength of 116 MPa and continuous use to 250-260°C; it is electrically insulative, V-0 flammability rated, and FDA compliant for food contact since 1998 [S3][S4].
30% glass-filled PEEK (Mil-P-46183 Type II Class 3, e.g. Victrex 450GL30, KetaSpire KT-820 GF30, VESTAKEEP 4000 GF30) cuts the coefficient of thermal expansion and lifts flexural modulus, making it the default for structural components held above 150°C where unfilled PEEK would drift dimensionally [S4]. 30% carbon-filled PEEK (Mil-P-46183 Type III Class 2, e.g. Victrex 450 CA30, KetaSpire KT-820 CF30) delivers roughly 3.5x higher thermal conductivity than unfilled PEEK, allowing bearing surfaces to shed heat faster and to carry higher PV loads [S4]. Bearing-grade compounds are a fourth family, with Victrex 450 FC30 (10% graphite / 10% carbon fibre / 10% PTFE) giving the lowest wear rate and highest PV limit in the polyketone set, and Victrex 450 FE20 (20% PTFE) cutting the coefficient of friction by about 50% and wear rate by 25% versus unfilled PEEK [S2].
Specialty Compounds Beyond the Big Four
Beyond the four commodity grades, PEEK is compounded with carbon nanotubes, glass/PTFE hybrids, and pigments for ESD-safe semiconductor wafer carriers, food-contact mixers (FDA / EU 10/2011), and oil-and-gas downhole seals rated to NACE MR0175-class service [S3][S4].
Drake Plastics and Ensinger both publish conductive and bearing sub-grades (TECAPEEK PVX, TECAPEEK ELS, SustaPEEK CF 30, Ketron HPV) targeted at sliding parts, while Boedeker offers medical and life-science sub-grades meeting USP Class VI and ISO 10993 biocompatibility, and a bearing grade qualified under Mil-P-46183 Type IV [S3][S4]. Victrex 450 FE20 (20% PTFE) is also FDA compliant for direct food contact, broadening its use to mixer seals and valve seats [S2].
Key Property Comparison Across the Main Grades
For a quick designer's pick, the four core grades line up against load, wear, thermal conductivity, and electrical behaviour as follows: unfilled PEEK, 116 MPa tensile, lowest modulus, V-0 insulative; 30% glass-filled, higher modulus and lower CTE, best for structural parts above 150°C; 30% carbon-filled, ~3.5x thermal conductivity of unfilled, best for heat-dissipating wear parts; bearing-grade 10/10/10 (450 FC30), lowest wear and highest PV, used in autoclave-tolerant bushings and helicopter components [S2][S3][S4].
The selection rule that recurs across supplier literature is straightforward: specify unfilled PEEK for chemical resistance and toughness, glass-filled for stiffness and dimensional stability, carbon-filled for load and thermal management, and PTFE/graphite bearing grades for sliding interfaces, rather than retrofitting one grade across all four roles [S2][S3][S4].
Selection Criteria and Operating Limits
PEEK retains mechanical properties in hot water and high-pressure steam, and unfilled grades are rated to 480°F (250°C) continuous with short-term peaks to 300°C, the reason they are specified for steam-sterilisable medical instruments and downhole tool components [S3][S4].
The polymer resists weak acids, weak alkalis, and most hydrocarbons, but is attacked by concentrated sulphuric acid, strong bases above moderate temperature, and certain halogenated solvents, so chemical compatibility must be cross-checked against the specific service fluid, not assumed from the PAEK label [S3]. Victrex PEK HT, a closely related polyetherketone rather than true PEEK, raises the glass-transition temperature and retains strength roughly 30°C higher than PEEK, but trades away some of the chemical resistance and fatigue performance of a true PEEK, an important distinction when reviewing data sheets labelled simply as "PEEK family" [S2].
Manufacturing Forms, Standards, and Sourcing
Stock shapes (rod, plate, tube, film) are typically extruded from Victrex PEEK 450G or KetaSpire KT-820 resin, while finished parts are produced by injection moulding, compression moulding, machining, or profile extrusion, with Mil-P-46183 (Types I-IV) governing unfilled, glass-filled, carbon-filled, and bearing-grade compositions [S3][S4].
Two resin suppliers dominate: Victrex (UK, the original ICI inventor from the early 1980s) and Solvay/Syensqo with KetaSpire, the only US-based PEEK resin producer, both meeting the same Mil-P-46183 standard, while VESTAKEEP (Evonik) and Mitsubishi Chemical Advanced Materials round out the qualified source list used by US and EU stockists [S2][S3][S4]. Aerospace sub-grades additionally meet UL 94 V-0 with low smoke and toxic-gas emission, the same flammability envelope cited for cabin interior brackets and electrical insulators [S2][S4]. For readers who need to compare PEEK against fibrous reinforcement systems used in adjacent aerospace and automotive programs, the S-2 glass vs E-glass spec guide and the automotive glass-fibre selection guide give a like-for-like spec baseline.
Who PEEK Is (and Is Not) For
PEEK earns its specification when a part must survive 250°C continuous service, repeated autoclave cycles, contact with hydrocarbons or steam, or strict flammability/smoke requirements such as UL 94 V-0 in aircraft cabins, conditions where PA66, POM, and PPS either soften, swell, or burn [S2][S3][S4].
PEEK is the wrong material when the load is modest, the temperature stays below 150°C, and the budget is tight: unfilled PEEK carries a 3-10x cost premium over PA66 or PPS, and for commodity structural parts the engineering-plastics selection map in engineering plastics: five major grades will usually point to a cheaper qualified resin. Where the service envelope stops at 200°C and chemical exposure is mild, PPS or PEI deliver most of the value at a fraction of the unit cost, while PEEK is reserved for the slices of the design space where the higher temperature ceiling, autoclave tolerance, and hydrocarbon resistance are non-negotiable [S3][S4].
Two signals to track over the next sourcing cycle: whether Solvay/Syensqo's KetaSpire KT-820 series continues to take share from Victrex 450G at the resin level, and whether PAEK/PEKK extrusion capacity additions translate into more competitive rod and plate pricing for 2027 stock-shape contracts [S2].
For component-level specifications, see construction machinery and equipment, lamps and light fittings, and lighting equipment and electric lamps.