PTFE O-rings are used mainly in the chemical, pharmaceutics and in medical engineering industry as static seals in flange connections, caps, etc. Due their good chemical resistance they are compatible with most liquids and chemicals. Extremely low temperatures will cause most rubber compounds to harden to the point where any elastomeric properties are no longer present in the material. This combined with contraction of the material can mean it will no longer function effectively as a seal. PTFE O-ring will be an ideal substitute material.