by Pete Spanos, Raffaele Bernardo and Montse Alvarez Grima, Arlanxeo
As the number one non-tire rubber by volume, ethylene propylene diene rubber (EPDM) based manufactured parts (e.g., seals, gaskets, grommets, hoses) are ubiquitously present in everyday life. EPDM is a non-polar polymer, which, due to its saturated backbone, features excellent resistance at high temperatures against oxidation, ozone and UV radiation. For this reason, it is the natural choice for all applications facing harsh environments, e.g., outdoor sealing, roofing and coolant hoses, to name a few. Depending on the monomer composition and relative ratios, the polymer can be either amorphous or semi-crystalline.
Some characteristics of EPDM are reported in table 1, in comparison with other common rubbers. The low EPDM polarity, while providing resistance to polar media, grants high compatibility with plasticizers like mineral oils and nonpolar fillers. Additionally, the low unsaturation ensures high chain flexibility (as seen by its highest entanglement density), allowing for high loading levels in the final rubber compounds. A sensible balance can be struck between compound cost and product properties.