Polychlorotrifluoroethylene (PCTFE or PTFCE) is a thermoplastic chlorofluoropolymer with the molecular formula , where n is the number of monomer units in the polymer molecule. It is similar to polytetrafluoroethene (PTFE), except that it is a homopolymer of the monomer chlorotrifluoroethylene (CTFE) instead of tetrafluoroethene. It has the lowest water vapor transmission rate of any plastic. History It was discovered in 1934 by Fritz Schloffer and Otto Scherer who worked at IG Farben Company, Germany. Trade names After World War II, PCTFE was commercialized under the trade name of Kel-F 81 by M. W. Kellogg Company in early 1950s. The name "Kel-F" was derived from "Kellogg" and "fluoropolymer", which also represents other fluoropolymers like the copolymer poly(chlorotrifluoroethylene-co-vinylidene fluoride) (Kel-F 800). These were acquired by 3M Company in 1957. But 3M discontinued manufacturing of Kel-F by 1996. PCTFE resin is now manufactured in different trade names such as Neoflon PCTFE from Daikin, Voltalef from Arkema or Aclon from Allied Signal. PCTFE films are sold under the tradename Aclar by Allied Signal. Tradenames of PCTFE in other manufacturing companies include Hostaflon C2 from Hoechst, Fluon from ICI, Aclar from Honeywell, Plaskon from Allied Chemical Corporation, Halon from Ausimont USA, and Ftoroplast-3 in USSR and Russian Federation. Synthesis PCTFE is an addition homopolymer. It is prepared by the free-radical polymerization of chlorotrifluoroethylene (CTFE) and can be carried out by solution, bulk, suspension and emulsion polymerization. Properties PCTFE has high tensile strength and good thermal characteristics. It is nonflammable and the heat resistance is up to 175 °C. It has a low coefficient of thermal expansion. The glass transition temperature (Tg) is around 45 °C. PCTFE has one of the highest limiting oxygen index (LOI). It has good chemical resistance. It also exhibits properties like zero moisture absorption and non wetting. It does not absorb visible light. When subjected to high-energy radiation, it undergoes degradation like PTFE. It can be used as a transparent film. The presence of a chlorine atom, having greater atomic radius than that of fluorine, hinders the close packing possible in PTFE. This results in having a relatively lower melting point among fluoropolymers, around 210–215 °C. PCTFE is resistant to the attack by most chemicals and oxidizing agents, a property exhibited due to the presence of high fluorine content. However, it swells slightly in halocarbon compounds, ethers, esters and aromatic compounds. PCTFE is resistant to oxidation because it does not