FFKM consists of TFE (trifluoroethanol as the main chain), PMVE (perfluoromethyl vinyl ether as the branch) and bridge. It not only has excellent heat-resistance and great chemical resistance (having resistance to more than 1600 chemicals) as PTFE (polytetrafluoroethylene), but also has high elasticity of rubber, which only has 50% deformation when pressed at the temperature of 300℃. FFKM can still maintain its elasticity and resilience when emerged in or in direct contact with corrosive liquid. In fact, the thermostability of FFKM is usually much better than those liquids. FFKM also have excellent air tightness (its vacuum resistance can be up to 1.33*10 -7pa~1.33*10 -8pa), high cleanliness and ionic resistance. Such characteristics are also widely used in the semi-conductor industry. FFKM is often used in the chemical industry and in highly corrosive media and places of high temperature.