Co-Curing of EPDM and Diene Rubbers by Grafting Accelerators Onto EPDM

Abstract

Abstract The object of this work was to find ways to co-cure blends of EPDM and diene rubbers for improved properties. We found that by grafting accelerators onto EPDM we obtain excellent cure compatibility between EPDM and natural rubber. The modified EPDM rubbers were obtained by reacting a benzene solution of EPDM with either 4,4′-dithiobismorpholine or 2-mereaptobenzothiazole (MBT). A method which grafts MBT onto EPDM in the presence of tert-butyl hypochlorite or other halogen donors is more versatile, and can be used for various EPDM rubbers regardless of the nature of the termonomers. We have proposed possible mechanisms by which the modified EPDM rubbers co-cure with natural rubber or other diene rubbers. In these mechanisms we point out the importance of the presence or the in situ formation of reactive sites in modified EPDM rubbers.