It is attacked by halogens and strong Brønsted and Lewis acids, as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures. It is highly resistant to thermal degradation, as well as to attack by both organic and aqueous environments. The thermal conductivity increases nearly linearly with temperature between room temperature and solidus temperature. Some grades have a useful operating temperature of up to 250 ☌ (482 ☏). PEEK has a glass transition temperature of around 143 ☌ (289 ☏) and melts around 343 ☌ (662 ☏). Its Young's modulus is 3.6 GPa and its tensile strength is 90 to 100 MPa. The processing conditions used to mould PEEK can influence the crystallinity and hence the mechanical properties. PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. The reaction is conducted around 300 ☌ in polar aprotic solvents - such as diphenyl sulfone. Typical is the reaction of 4,4'-difluorobenzophenone with the disodium salt of hydroquinone, which is generated in situ by deprotonation with sodium carbonate. PEEK polymers are obtained by step-growth polymerization by the di alkylation of bis phenolate salts. The polymer was first developed in November 1978, initially being brought to the market in the early 1980s by the part of Imperial Chemical Industries (ICI) that became Victrex PLC. Polyether ether ketone ( PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family, used in engineering applications.
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