What is PEEK used for?

PEEK is used where metal-like stiffness is needed at temperatures or chemical exposures that destroy cheaper plastics — bushings and bearings running unlubricated, pump wear rings, compressor valve plates, semiconductor wafer handling parts, aircraft interior components, and spinal and dental implants. It is one of the few polymers approved for repeated steam and gamma sterilisation.

What is the maximum temperature for PEEK?

Melting point is 343 °C (649 °F) and the maximum continuous service temperature in air is 250 °C (482 °F), with short-term excursions to about 300 °C. The practical limit for a load-bearing part is lower than the service temperature — the deflection temperature under load (HDT) is 152 °C at 1.8 MPa. Size the part for the temperature at which it must still carry load, not the melting point.

Is PEEK better than PTFE?

They solve different problems. PEEK is far stronger and stiffer (100 MPa vs 20–35 MPa tensile) and holds properties to 250 °C, but has a higher coefficient of friction (0.34 vs 0.04–0.10). PTFE is softer and weaker but has the lowest friction of any solid and is almost universally chemically inert. Choose PEEK for load and temperature; PTFE for friction and chemical resistance.

Several unfilled PEEK grades carry FDA food-contact and EU 10/2011 compliance, and PEEK is widely used in medical implants. Food-contact status is grade-specific — confirm the specific grade's regulatory listing before specifying it for food or medical use.

Can PEEK be machined?

Yes, but it is more demanding than Delrin. PEEK is abrasive, generates significant heat, and can stress-crack if overheated or over-clamped. Use sharp carbide tooling, high positive rake, generous coolant, and light finishing passes. For tight-tolerance work, stress-relieve the stock by annealing before final machining.

Why is PEEK so expensive?

The monomer (difluorobenzophenone and hydroquinone) is costly and the polymerisation is a high-temperature condensation reaction, so raw polymer costs many times more than commodity engineering plastics. Typical relative cost is 8–12× Delrin and 2–3× PTFE. For parts that do not actually need its temperature or chemical performance, a cheaper material is normally the better engineering choice.

PEEK (Polyetheretherketone)

Property data sheet for unfilled PEEK — mechanical, thermal, electrical and physical values with ASTM test methods — plus the temperature limits that drive most material selection decisions and a comparison with PTFE, Delrin and Nylon.

Data verified 2026-09-29 · based on ASTM D6262-16

Mechanical Properties

Property	Metric	Imperial	Test method
Tensile strength, yield	100 MPa	14,500 psi	ASTM D638
Tensile modulus	3.6 GPa	520 ksi	ASTM D638
Elongation at break	45 %	45 %	ASTM D638
Flexural strength	170 MPa	25,000 psi	ASTM D790
Flexural modulus	4.1 GPa	600 ksi	ASTM D790
Compressive strength	130 MPa	19,000 psi	ASTM D695
Hardness, Rockwell M	99	99	ASTM D785
Izod impact, notched	3.5 kJ/m²	—	ASTM D256
Coefficient of friction	0.34	0.34	ASTM D3702

Thermal Properties

Property	Metric	Imperial	Test method
Melting point	343 °C	649 °F	ASTM D3418
Glass transition temperature (Tg)	143 °C	289 °F	ASTM E1356 (DSC)
Deflection temperature @ 1.8 MPa (264 psi)	152 °C	306 °F	ASTM D648
Max continuous service temperature, air	250 °C	482 °F	UL 746B
Coefficient of linear thermal expansion	47 µm/m·°C	26 µin/in·°F	ASTM D696
Thermal conductivity	0.25 W/m·K	1.7 BTU·in/h·ft²·°F	ASTM C177
Flammability	UL94 V-0	UL94 V-0	UL 94

Electrical & Physical Properties

Property	Metric	Imperial	Test method
Volume resistivity	1.6 × 10¹⁶ Ω·cm	—	ASTM D257
Dielectric strength	23 kV/mm	585 V/mil	ASTM D149
Dielectric constant @ 1 MHz	3.2	—	ASTM D150
Specific gravity / density	1.30 g/cm³	—	ASTM D792
Water absorption, 24 h	0.15 %	—	ASTM D570
Water absorption at saturation	0.40 %	—	ASTM D570

PEEK Grades and What Changes Between Them

Unfilled PEEK is the baseline. Most industrial PEEK is a filled or modified grade, and the filler — not the polymer — usually drives the selection.

Grade	Filler	What it improves	Typical use
Unfilled (450G)	None	Best elongation and impact; highest purity	Seals, bearings, semiconductor and medical parts
30% glass-filled	Glass fibre	Stiffness and creep resistance, lower CTE	Structural parts under sustained load at temperature
30% carbon-filled	Carbon fibre	Highest stiffness and strength; wear resistance; conductive	High-load bearings, pump wear rings, compressor parts
PTFE / graphite filled	PTFE, graphite	Lower friction and wear, higher PV limit	Bushings and bearings running against steel
Bearing grade (Ketron® HPV etc.)	Multi-filler	Optimised wear rate at high PV	Unlubricated bearings and thrust washers

Practical note: adding filler raises stiffness and lowers elongation. A 30% glass-filled grade is roughly twice as stiff as unfilled but loses most of its impact toughness. Choose unfilled when toughness or purity matters; choose filled when stiffness, creep or wear matters.

PEEK vs PTFE vs Delrin vs Nylon

Property	Property	PEEK	PTFE	Delrin (POM-H)
Density (g/cm³)	1.30	2.16	1.42	1.14
Tensile strength (MPa)	100	20–35	75.8	82.7
Melting point (°C)	343	327	175	265
Max continuous use (°C)	250	260	85	105
Water absorption, 24 h (%)	0.15	0.01	0.25	1.2–1.5
Coefficient of friction	0.34	0.04–0.10	0.20	0.25–0.40
Machinability	Fair	Excellent	Excellent	Good
Relative cost	8–12×	3–5×	1×	1×

Comparison values are typical published figures for unfilled grades. How to choose: PEEK where the part must survive above 150 °C, resist aggressive chemicals, or hold stiffness at temperature; PTFE where minimum friction or full chemical inertness matters and loads are low; Delrin for stiff, dimensionally stable parts at moderate temperature and low cost; Nylon for tough, low-cost parts where moisture swelling is acceptable.

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Frequently Asked Questions

What is PEEK used for?: PEEK is used where metal-like stiffness is needed at temperatures or chemical exposures that destroy cheaper plastics — bushings and bearings running unlubricated, pump wear rings, compressor valve plates, semiconductor wafer handling parts, aircraft interior components, and spinal and dental implants. It is one of the few polymers approved for repeated steam and gamma sterilisation.
What is the maximum temperature for PEEK?: Melting point is 343 °C (649 °F) and the maximum continuous service temperature in air is 250 °C (482 °F), with short-term excursions to about 300 °C. The practical limit for a load-bearing part is lower than the service temperature — the deflection temperature under load (HDT) is 152 °C at 1.8 MPa. Size the part for the temperature at which it must still carry load, not the melting point.
Is PEEK better than PTFE?: They solve different problems. PEEK is far stronger and stiffer (100 MPa vs 20–35 MPa tensile) and holds properties to 250 °C, but has a higher coefficient of friction (0.34 vs 0.04–0.10). PTFE is softer and weaker but has the lowest friction of any solid and is almost universally chemically inert. Choose PEEK for load and temperature; PTFE for friction and chemical resistance.
Is PEEK food safe?: Several unfilled PEEK grades carry FDA food-contact and EU 10/2011 compliance, and PEEK is widely used in medical implants. Food-contact status is grade-specific — confirm the specific grade's regulatory listing before specifying it for food or medical use.
Can PEEK be machined?: Yes, but it is more demanding than Delrin. PEEK is abrasive, generates significant heat, and can stress-crack if overheated or over-clamped. Use sharp carbide tooling, high positive rake, generous coolant, and light finishing passes. For tight-tolerance work, stress-relieve the stock by annealing before final machining.
Why is PEEK so expensive?: The monomer (difluorobenzophenone and hydroquinone) is costly and the polymerisation is a high-temperature condensation reaction, so raw polymer costs many times more than commodity engineering plastics. Typical relative cost is 8–12× Delrin and 2–3× PTFE. For parts that do not actually need its temperature or chemical performance, a cheaper material is normally the better engineering choice.

Value Sources

Each data column on this page is tied to the source it came from. The numbers in square brackets correspond to the table headers above.

#	Source	Type	Revision / method
[1]	Unfilled PEEK (450G class) published data sheets	standard	supplier data sheets, retrieved 2026-09

Data Sources

Standard	Revision	What it covers on this page
ASTM D6262 — Standard Specification for Extruded PEEK Shapes	ASTM D6262-16	specification basis for unfilled PEEK shapes and properties
Individual ASTM test methods	current revisions as of 2024 (methods cited per property)	each mechanical, thermal and electrical property value

Cross-checked against:

Supplier-published unfilled PEEK (450G class) data sheets — values consistent across at least three suppliers

Values are typical published figures for the grade stated. Property data for filled or modified grades differs substantially — use the specific grade data sheet for design work.

Accuracy and use. The values on this page are compiled from the published standards and cross-checked sources listed above. Where values are derived, the derivation is stated. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Every value on this page is traceable to the sources listed above. If you use the data in a document, paper or report, cite it as:

Plain text

Engineering Reference. "PEEK Properties." https://refmanual.com/materials/peek/ (accessed 2026-09-29). Data from ASTM D6262 — Standard Specification for Extruded PEEK Shapes, ASTM D6262-16.

BibTeX

@misc{peek,
  title        = {PEEK Properties},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/materials/peek/}},
  note         = {Accessed: 2026-09-29},
  source       = {ASTM D6262 — Standard Specification for Extruded PEEK Shapes, ASTM D6262-16}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - PEEK Properties
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/materials/peek/
PY  - 2026
DA  - 2026-09-29
N1  - Source: ASTM D6262 — Standard Specification for Extruded PEEK Shapes, ASTM D6262-16
ER  -

Each row in the tables above also has a permanent link — hover a row and use the # link to cite a single value rather than the whole page.