Buna is designed to have a resistance to oil, hydrocarbons and chemicals. It is readily used in the brewing world, as well as in the crude oil and petrochemical industries. At -40 to 212 Fahrenheit, Buna has less range of temperature than EPDM.
EPDM (ethylene-propylene-diene-monomer) is a synthetic rubber designed for water applications, is rated for -70 to 300 degrees Fahrenheit and has a high resistance to damage caused by heat, pressure, UV rays, acetone, alkalis and ozone.
Viton is designed to handle strong acids, petroleum products, solvents and oils. It is not recommended for use with hydrocarbons, ketones and steam. Viton has a temperature rating of +5 to +400 Fahrenheit.