ZFV NBR lined butterfly valve. Seat/linbed material is NBR ( nitrile rubber ), which have good performance anti-oil, often be used for oil seal. Below are other soft material produced as valve seat/ line :

NR ( Natural rubber ) NR good elasticity, good overall performance, but poor cold and poor alkali resistance.

EPDM ( ethylene propylene diene rubber ), good insulation for wear-resistant materials or high-pressure electrical materials

Neoprene rubber. good wear resistance, for the mat Chlorosulfonated polyethylene CSM cold good

Polytetrafluoroethylene ( PTFE / TEFLON ) 

Plastic king, excellent acid and alkali resistance, can be resistant to fluoride. Uses a wide range of corrosive liquid can be used for the pipeline.