What is the difference between EP, EPR, and EPDM?

EPR is an abbreviation for Ethylene-propylene copolymer, while EPDM is an abbreviation for Ethylene-Propylene Terpolymer. From a functional standpoint, there are very few performance differences between EPR and EPDM. Both swell dramatically in petroleum products, and both are excellent in water, steam, and polar solvents like MEK and acetone. However, there are some notable performance differences in extremely demanding applications: EPRs or very tightly cured EPDMs are suited for the nuclear industry (E0740-75 is recommend), and for applications involving concentrated acetic acid, some EPDM compounds (like E0692-75) show superior performance to most EPRs. In other applications, the performance difference is very difficult to identify.