Polyether ether ketone (PEEK) is a colourless organic polymer thermoplastic in the polyaryletherketone (PAEK) family, used in engineering applications.

Synthesis [edit]

PEEK polymers are obtained by step-growth polymerization by the dialkylation of bisphenolate salts. Typical is the reaction of 4,4'-difluorobenzophenone with the disodium salt of hydroquinone, which is generated in situ by deprotonation with sodium carbonate. The reaction is conducted around 300 °C in polar aprotic solvents - such as diphenyl sulphone.^[2][3]

Properties [edit]

PEEK is a semicrystalline thermoplastic 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.^[4] PEEK has a glass transition temperature at around 143 °C (289 °F) and melts around 343 °C (662 °F). The thermal conductivity increases nearly linearly versus temperature between room temperature and solidus temperature.^[5] It is highly resistant to thermal degradation as well as attack by both organic and aqueous environments. It is attacked by halogens and strong Bronsted and Lewis acids as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures. It dissolves completely in concentrated sulfuric acid at room temperature.

Applications [edit]

Because of its robustness, PEEK is used to fabricate items used in demanding applications, including bearings, piston parts, pumps, HPLC columns, compressor plate valves, and cable insulation. It is one of the few plastics compatible with ultra-high vacuum applications. PEEK is considered an advanced biomaterial used in medical implants. It is extensively used in the aerospace, automotive, teletronic,^{[clarification needed]} and chemical process industries.^[6] PEEK's mechanical properties at elevated temperatures have led to it being used in at least two varieties of Reprap extruder as thermal insulation. This means the main mechanical structure of the extruder can be made of the same material that is being extruded, provided that the PEEK insulator prevents heat from traveling beyond the intended melt zone. A disadvantage is the high price, which limits its application to high value items.

Shape memory PEEK in biomechanical applications [edit]

PEEK is not traditionally a shape memory polymer; however, recent advances in processing have allowed shape memory behavior in PEEK with mechanical activation. This technology has expanded to applications in orthopedic surgery.^[7]

References [edit]

1. ^ A.K. van der Vegt & L.E. Govaert, Polymeren, van keten tot kunstof, ISBN 90-407-2388-5
2. ^ David Parker, Jan Bussink, Hendrik T. van de Grampe, Gary W. Wheatley, Ernst-Ulrich Dorf, Edgar Ostlinning, Klaus Reinking (15 April 2012). "Polymers, High-Temperature". Ullmann's Encyclopedia of Industrial Chemistry (online version). Wiley-VCH, Weinheim,. doi:10.1002/14356007.a21_449.pub3.  (subscription required)
3. ^ David Kemmish "Update on the Technology and Applications of PolyArylEtherKetones" 2010. ISBN 978-1-84735-408-2.
4. ^ Material Properties Data: Polyetheretherketone (PEEK), www.makeitfrom.com
5. ^ J. Blumm, A. Lindemann, A. Schopper, "Influence of the CNT content on the thermophysical properties of PEEK-CNT composites", Proceedings of The 29th Japan Symposium on Thermophysical Properties, October 8–10, 2008, Tokyo
6. ^ Lauzon, Michael (May 4, 2012). "Diversified Plastics Inc., PEEK playing role in space probe". PlasticsNews.com. Crain Communications Inc. Retrieved May 6 2012. 
7. ^ Anonymous. "Surgical Technologies; MedShape Solutions, Inc. Announces First FDA-cleared Shape Memory PEEK Device; Closing of $10M Equity Offering". Medical Letter on the CDC & FDA.