PTFE O-rings and seals

PTFE (Polytetrafluoroethylene, Teflon®)

PTFE is a flexible, chemical and thermal resistant material which is also non-stick and electrically resistant. It is a tough polymer possessing an impressive working temperature range.

PTFE seals are used where many other materials and elastomers are unsuitable for the application conditions, i.e. friction, chemical resistance and temperature. It is used for a wide range of applications in many industries, including aerospace, food and drink, pharmaceuticals, telecommunications and semi-con. It is flexible, chemical resistant, non-stick and electrically resistant and is superior to most other materials in these conditions. Hardness is measured using the Shore D scale and is usually 54 – 57° (this equates to approx. 98° on the Shore A scale).

PTFE is the most chemically inert of the sealing materials. It is resistant to most chemicals including acids, bases, oils, and steam. PTFE is a very tough material, offering outstanding tear resistance and abrasion resistance. This material’s slippery surface properties make it advantageous for sealing in moving systems such as mass spectrometer probes and valves.

It is worth noting that this material is not easily compressed, and therefore may not seal as easily as some of the other polymers.

Common fillers for PTFE materials are glass fibre, carbon graphite and molybdenum disulphide.

Special care is to be taken during installation of PTFE seals.

Thermal properties

PTFE has a high melting point of 342°C which allow parts to be manufactured to provide a wide operating temperature of -185°C to + 260°C. Above this temperature the material properties decrease causing degradation.

PTFE is used in cryogenic temperatures to seal media such as liquid hydrogen, nitrogen and helium.