Polytetrafluoroethylene (PTFE)
PTFE (Polytetrafluoroethylene) belongs to the class of thermoplastic polyhalogenolefins.
PTFE is highly inert and thermally stable up to 260°C (500°F). Even aggressive acids such as aqua regia cannot corrode PTFE; it is also extremely resistant against all bases, alcohols, ketones, fuels, oils etc.
PTFE has a very low friction coefficient. There is virtually no material that can adhere to PTFE, as its surface energy is extremely low. PTFE is very hard to wet and almost impossible to glue. Its angle of contact with water is 126°.
Due to its chemical inertness, PTFE is used as a coating for applications which include aggressive chemicals. The great variety of possible compounds and the relatively simple solutions provided by this allow for the preparation of highly specific mixtures for a wide spectrum of applications such as shaft seals, groove seals, bellows, or screw joints.
Due to its low friction properties, PTFE is relevant as a dry lubricant (solid lubricant) and as a coating for bearings and seals.
In medical applications, PTFE is used for implants, among other things. On the one hand, its remarkable chemical resistance makes for high durability and good compatibility, on the other hand its smooth surface reduces the risk of blood clotting.
Because it is extremely heat resistant, PTFE can be autoclaved at 130 °C (270 °F). There are also PTFE face implants, which are used in plastic surgery.
In high frequency technology, PTFE is a popular material e.g. for cable insulation, due to its low permittivity and its minimal losses.
In high voltage technology, PTFE is suitable as an electrical insulator due to its high partial discharge resistance and its low adhesive properties regarding surface contamination.
Expanded or elongated PTFE (ePTFE) is a specially processed form of polytetrafluoroethylene with a membrane so fine-pored that it is permeable to steam, but not to water in its liquid state. It thus lends itself to the manufacturing of waterproof, breathable foils for the clothing industry and medical technology.
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