EPDM
EPDM is the abbreviated name for Ethylene Propylene Diene Monomer.Ingeneral industry,one may see other abbreviations or trade names used in lieu of EPDM such as EPT.Nordel or EPR.All of these are the members of EPDM family.
EPDM is a general seat material of resilient-seated butterfly.It is a terpolymerof ethylene,propylene and the third unsatur ated component tp be sulfurated.It features very excellent heat,weather and ozone resistance,processibility and electrical properties.

BUNA-N
BUNA-N isa copolymer of butadiene and acrylonitrile.It is produced in different ratios varying from 25:75 to 75:25.It has been excellent resistance to oils and solvents.(resistance to oils is proportional to acrylonitrile content) and fair resistance to ozone and UV,but not resistance to strong oxidizing chemicals.

VITON
VITON is a fluoroelastomer copolymer of vinyldiene fluoride and hexafluoropropylene.It was well know for its chemical resistance,heat resistance,oxidation resistance and good resistance to fuels containing up to 30% aromatics,but is mostly poor resistance in solvents.

Neoprene
Neoprene is a polymer of chloroprene and it was the world's  first synthetic elastomer,with oil resistance that stii make it a top performer today.It offers a good resistance to aging and attack by ozone, sunlight and moderately elevated temperature.It may resis various oils,gasoline and some aromatic or halogenated solvents.