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. These were acquired by 3M Company in 1957. 3M discontinued manufacturing of Kel-F by 1996.
PCTFE resin is now manufactured under different trade names such as Neoflon PCTFE from Daikin, Voltalef from Arkema, and Aclon from Honeywell. PCTFE films are sold under the tradename Aclar by Honeywell. Other current and former trade names of PCTFE include Hostaflon C2 from Hoechst, Fluon from ICI, Plaskon from Allied Chemical Corporation, Halon from Ausimont USA, and Ftoroplast-3 in the 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 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.
PCTFE exhibits a permanent dipole moment due to the asymmetry of its repeating unit. This dipole moment is perpendicular to the carbon-chain axis.
Differences from PTFE
PCTFE is a homopolymer of chlorotrifluoroethylene (CTFE), whereas PTFE is a homopolymer of tetrafluoroethylene. The monomers of the former differs from that of latter structurally by having a chlorine atom replacing one of the fluorine atoms. Hence each repeating unit of PCTFE have a chlorine atom in place of a fluorine atom. This accounts for PCTFE to have less flexibility of chain and hence higher glass transition temperature. PTFE has a higher melting point and is more crystalline than PCTFE, but the latter is stronger and stiffer. Though PCTFE has excellent chemical resistance, it is still less than that of PTFE. PCTFE has lower viscosity, higher tensile strength and creep resistance than PTFE.