PTFE (also known as Teflon®) is considered the industry standard (for valves) for soft sealing components due to its almost universal chemical resistance and its low coefficient of friction. It also happens to have some fantastic characteristics:
Almost totally unaffected by chemicals encountered in commercial use.
Heat resistant – retains its properties after exposure to temperatures beyond the limit of almost all other thermoplastics & elastomers.
Low coefficient of friction
Chemically pure and inert
Low surface energy in the solid state
Retains its excellent properties even at cryogenic temperatures
Excellent chemical resistance over broad temperature range
Excellent retention of properties after a long period of time
Has light stability – does not change appearance after exposure to UV or infrared
Stable dielectric properties
Inert to microbiological and enzymic attack
Completely resistant to hydrolysis – good barrier for water permeation, even after long periods in water