PEEK is a semicrystalline thermoplastic material with excellent mechanical and chemical resistance properties that are retained to high temperatures. The Young’s modulus is 3.6 GPa and its tensile strength 90 to 100 MPa. PEEK has a Tg around 143 °C and melts around 343 °C. The thermal conductivity increases nearly linearly versus temperature between room temperature and solidus temperature. It is highly resistant to thermal degradation as well as attack by both organic and aqueous environments. It is attacked by halogens and strong acids as well as some halogenated compounds and aromatic hydrocarbons at high temperatures. It dissolves completely in concentrated sulfuric acid at room temperature.
Because of its robustness, PEEK is used to fabricate items used in demanding applications, including bearings, piston parts, pump components, HPLC and compressor valve plates. It is one of the few plastics compatible with ultrahigh vacuüm applications.
It is extensively used in the aerospace, automotive, teletronic, and chemical process industries.