Polyether ether ketone (PEEK)
Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family, used in engineering applications. The polymer was first developed in November 1978, later being introduced to the market by Victrex PLC, then Imperial Chemical Industries (ICI) in the early 1980s
Polyaryletherketones (PAEKs) are a class of semi-crystalline high performance engineering thermoplastics having a unique combination of thermal stability, chemical resistance, and excellent mechanical properties over a wide temperature range. This class of polymers has also good resistance to combustion and good electrical performance.
The high thermal stability is provided by the diphenylene ketone groups which impart high strength and high resistance to oxidation, but make the polymer rigid. Flexibility in the polymer backbone is provided by ether linkages which also add to the thermal stability. Some types, like PEEK1, are extremely tough and have very high impact strength. Due to the semi-crystalline nature of these polymers, a high degree of mechanical properties is retained close to their melting temperature. They also have very low tendency to creep and good sliding and wear properties. These properties are retained over a wide temperature range.
Polyetherketones are known for their excellent chemical resistance to many organic and inorganic chemicals and exceptionallly good resistance to hydrolysis in hot water. However, they exhibit poor or only moderate resistance to weathering due to damage caused by UV radiation2, whereas resistance to beta, gamma and X-rays is good.
Some grades of PAEKs show good resistance to combustion, and when they burn, they produce fewer toxic and corrosive gases than many other high performance polymers.
Most grades can be fabricated by conventional thermoplastic processing methods, such as extrusion and compression molding. PEKs can be also used as matrix resins for high performance reinforced composites.