Introduction
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. The best known brand name of PTFE-based formulas is Teflon by Chemours.
PTFE is a fluorocarbon solid, as it is a high-molecular-weight compound consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE, as fluorocarbons demonstrate mitigated London dispersion forces due to the high electronegativity of fluorine. PTFE has one of the lowest coefficients of friction of any solid.
Polymerization of PTFE
Preparation of monochlorodifluoromethane and Tetrafluoroethylene (TFE): Reaction of hydrofluoric acid with Chloroform yields monochlorodifluoromethane
CHCl3 + 2HF CHClF2 + 2HCL
Purification of TFE:
Pure monomer is required for polymerisation. If impurities are present it will affect the final product. The gas is first scrubbed to remove any hydrochloric acid and then distilled to separate other impurities.
Pure uninhibited Tetrafluoroethylene can polymerise with violence, even at temperatures initially below that of room temperature. A silver-plated reactor, quarter-filled with a solution consisting of 0.2 parts ammonium persulphate, 1.5 parts borax and 100 parts of water, and with a pH of 9.2. The reactor was closed; evacuated and 30 parts of monomer were let in. The reactor was agitated for one hour at 80°C and after cooling gave an 86% yield of polymer.
PTFE is made commercially by two major processes, one leading to the so called 'granular' polymer and the second leading to a dispersion of polymer of much finer particle size and lower molecular weight. One method of producing the latter involved the use of a 0.1°% aqueous disuccinic acid peroxide solution. The reactions were carried out at temperature up to 90°C.
Properties
PTFE properties include high molecular weight, hydrophobility, low coefficient of friction, thermoplasticity, good dielectric properties, high electronegativity, and low chemical reactivity.
Applications
The major application of PTFE such as: