PEEK (polyether etherketone), PEK (polyether ketone), and PAEK (polyaryl etherketone) are a family of partially crystalline engineering thermoplastics (plastic polymers) that can be used at high temperatures. These resins have excellent chemical resistance. Their high thermal stability comes from rigid ketone and phenyl groups, while their high strength and thermoplastic state below the decomposition temperatures come from the ether groups.

These compounds can have melting temperatures in excess of 650 degrees Fahrenheit, with mechanical properties retained to about 500 degrees Fahrenheit.

Tensile properties are comparable to most engineering thermoplastics. Creep resistance is outstanding and may sustain large stresses over a useful service life without measurable strain.

Wear rates and friction are becoming increasingly important against metals. Corrosion protection, too, is often an integral part. For these reasons, PEEK (and related polymers) are becoming increasingly important, as demands on them for their structural properties grow, particularly at elevated temperature.

Friction from composites of thermoplastic vary in a unique way from metals in that their asperities (surface irregularity) will deform much more under load. Consequently, friction between a thermoplastic and metal surface is typically characterized by adhesion deformation disproportionally lower to load. The primary mechanism is adhesive wear, which is characterized by fine particles of polymer removed from the surface. This is a good illustration that the surfaces are wearing properly. (Large gouges or corrugations in a polymer surface would suggest not adhesion wear, but abrasion wear or the material’s pressure velocity limit was violated.

Wear factors of PEEK plastics, PEK or PAEK appear much less affected by load and speed components, independent of PV. Wear performance seems to be better at low pressures and high speeds, rather than high pressures and intermediate speeds. All display excellent resistance to wear over wide ranges of pressure, velocity, temperature, and counterface roughness.

Properties of some of the PEEK coating or PEEK plastic plastic are now characteristic of PTFE (polytetrafluoroethylene). The advantage is in markets requiring dry lubrication, low friction or non stick properties, where improved resistance to abrasion is key.