Teflon O-rings are made from a hard, rigid plastic with high temperature and outdoor element resistance. The mechanical properties of Teflon are low compared to those of O-ring rubber, because it is a rigid material and won't seal well, but O-rings made of Teflon are perfect for a few applications, including paint guns and automotive steering systems.
The Teflon material occasionally used to produce o-rings often contains additives such as glass, carbon, graphite and bronze, which provide enhanced mechanical strength, stability and wear resistance. Using metal as filler for rubber o-rings is also utilized in reverse, since many metal o-rings have plastic elements to fill their shape out too. This practice ensures that o-rings will seal the space between two parts of a machine or pipe system to the very best of its ability. When additives are used, Teflon o-rings are valuable in a number of different applications within the automotive, medical pharmaceutical, electrical appliance and aerospace industries. Specific applications can include brake systems, hydraulic cylinders, pistons, heat exchangers and various water pumps. Although not as flexible as other types of rubber o-rings such as silicone and Viton, Teflon o-rings are still employed.
Teflon O-Rings - Allied Metrics Seals & Fasteners, Inc.