Home · Materials · PEEK
Engineering Plastic

PEEK

PEEK is a high-performance semi-crystalline engineering plastic combining a 250 C service temperature, 100 MPa tensile strength, top-rated chemical resistance, and biocompatibility. At 1.32 g/cm3 it is light yet strong, but at the highest cost tier it is reserved for parts where metals are too heavy or conventional plastics cannot survive the environment.

How PEEK machines

PEEK machines reasonably well at 3/5 with sharp carbide tools, but it builds internal stress during cutting. Stock and finished parts should be annealed to relieve residual stress and prevent cracking or warping, especially on thin sections and tight tolerances. Its abrasiveness and high cost reward careful, proven toolpaths over aggressive material removal.

Manufacturing & processing

PEEK is CNC machined from rod and plate or injection molded for production volumes. Annealing is the critical processing step: stress-relieve raw stock before machining and again after rough cuts to stabilize dimensions. It tolerates steam, autoclave, and aggressive chemicals, so it suits parts requiring repeated sterilization.

Typical applications

PEEK serves medical implants and instruments, semiconductor handling, aerospace brackets, downhole oil and gas seals, high-temperature bearings, valve seats, and chemical pump components. Its strength, chemical inertness, and 250 C rating let it replace metal in lightweight, corrosion-critical, and electrically insulating assemblies.

When to choose it

Choose PEEK when service temperature, chemical attack, or sterilization defeats cheaper plastics and weight rules out metal. If you only need temperatures to 170 C, Ultem PEI costs less; for non-structural high-temp insulation PTFE may suffice. Avoid PEEK's premium cost when a commodity engineering plastic meets the requirements.

Suitable surface finishes

Common finishes for PEEK: bead blasting, powder coating. Use the finish selector →

FAQ

Why must PEEK be annealed?
Machining and molding lock residual stress into PEEK. Without annealing, parts can crack, craze, or distort over time and during use. A controlled heat soak relieves this stress and stabilizes the crystalline structure, which is essential for tight tolerances, thin walls, and reliable high-temperature service.
Can PEEK really replace metal?
In the right roles, yes. At 100 MPa tensile and 250 C service, PEEK substitutes for metal in lightweight, corrosion-resistant, electrically insulating, and non-magnetic parts. It will not match steel or titanium strength or stiffness, so it suits moderate-load components, not heavily stressed structural members.
Why is PEEK so expensive?
PEEK sits at the top cost tier because the base polymer is costly to synthesize, stock is expensive, and machining demands annealing and careful tooling. Reserve it for parts where temperature, chemical, biocompatibility, or weight requirements genuinely rule out lower-cost plastics or metals.

Property values are typical/nominal for early guidance and vary by temper, grade, supplier and heat treatment. Confirm critical specs against a certified datasheet or with an mfgiq engineer.