PEEK
A very high-performance engineering polymer
Typical values for the temper in the title
PEEK is a semi-crystalline polymer of the PAEK family, considered the "king" of engineering plastics. It combines high strength and stiffness, continuous service up to about 250–260 °C, very broad chemical resistance, wear and radiation resistance, and low flammability.
Thanks to this combination it replaces metals in lightweight parts: aerospace, oil and gas, medical implants (medical grade per ASTM F2026), electronics, and parts running hot and in sliding. It is very expensive, so it is chosen only when a cheaper material is not enough.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 100 MPa | |
| Elongation A | 50% | |
| Modulus of elasticity E | 3.6 GPa | |
| Density ρ | 1.32 g/cm³ | |
| Max continuous service temperature | 260°C | |
| Heat deflection temperature (HDT) | 160°C | |
| Machinability | 55% | relative rating in the site database |
Structure and family
| Feature | Value | Meaning |
|---|---|---|
| Type | semi-crystalline thermoplastic | strength and chemical resistance |
| Family | PAEK (polyaryl ether ketone) | |
| Tg glass transition | about 143 °C | stiffness drops above it |
| Tm melting | about 343 °C |
Typical values per producer data sheets.
Grades and versions
In engineering polymers, the choice is between an unfilled grade, filled grades (glass or carbon fiber) and special grades (bearing, medical, food). Filler strongly changes strength, stiffness and expansion.
| Version | Properties | When to choose it |
|---|---|---|
| Unfilled | ductile, maximum chemical resistance | general use, medical |
| Glass-fiber filled (GF30) | stiffer and stronger | structural parts |
| Carbon-fiber filled (CF30) | very strong and stiff, light | metal replacement |
| Bearing grade (CF/PTFE/graphite) | low friction and wear | bearings and rings |
Applications
- Aerospace and space parts
- Seals and rings in oil and gas
- Medical implants and instruments
- Bearings and gears at temperature
- Electronic components
Fabrication
Machining
Use very sharp tools, a feed that does not overheat the material, and good support (the material is flexible and deforms under clamping). For precision parts, stress-relief annealing before final machining is sometimes performed.
Joining
Ultrasonic or laser welding, bonding after surface treatment, and mechanical assembly.
Thermal expansion
The expansion coefficient of an unfilled polymer is several times that of a metal. In a precision part or an assembly with metal, design clearances accordingly.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| PEEK CF30 | 212 MPa | — | PEEK with 30% carbon fiber · material page |
| PEI (Ultem) | 105 MPa | Ultrasonic | PEI: amorphous, cheaper, less chemically resistant · material page |
| 6061-T6 | 310 / 276 MPa | Good — ER4043 | aluminum: stronger and stiffer, twice as heavy · material page |
Common mistakes
Designing to room-temperature strength for hot use
Above about 143 °C (Tg) stiffness drops. Design to producer data at temperature.
Choosing PEEK where POM or PA is enough
The price difference is very large.
Machining a precision part without annealing
Internal stresses release and distort the part.
Equivalents, standards and supply
| ISO | PEEK |
|---|---|
| ASTM | D8033 |
| Standards | ASTM D8033 / ASTM F2026 (medical) |
| Forms | plate · rod · pellets · pipe |
| Producers | Victrex PEEK · Solvay KetaSpire · Evonik Vestakeep |
Learn more
Values are typical for an unfilled grade (unless stated otherwise) and for comparison only. In polymers, properties depend on grade, filler, temperature, moisture and load duration. For design, rely on the producer data sheet for the specific grade. Sources: ASTM classification standards (D8033, D5205, D5204, D6394, D4067 and others), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026