Polyetherketone (PEK) - Polyetherketone, also known as polyaryletherketone, is an advanced thermoplastic resin having both ether and ketone linkages in its chains. PEK materials are semicrystalline aromatic polyesters with excellent mechanical and dielectric properties. Polyetherketone is also highly fire-resistant, has good chemical resistance, and can be used for high temperature applications. Polyetheretherketone (PEEK) is the most common and widely sold member of the polyetherketone family.