Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene.
The most well-known brand name is Teflon by DuPont.
PTFE is an extremely inert material and is unaffected by virtually every known chemical including most acids, alkalis and solvents. The exceptions are molten alkali metals, fluorine gas, and elemental fluorine
PTFE has one of the lowest coefficients of friction against any solid.
The lack of elasticity is often a disadvantage in PTFE O-rings.
It has no “memory” and is subject to creep. This is advantageous when used as a seal, because the material creeps a small amount to conform to the mating surface. However, to keep the seal from creeping too much, fillers are used, which can also improve wear resistance and reduce friction.
Often, metal springs are used to apply continuous force to PTFE seals to give good contact, while permitting a beneficially low percentage of creep.
PTFE is hydrophobic: neither water nor water-containing substances wet PTFE.