Melt grafting of maleic anhydride onto an ethylene–propylene–diene terpolymer (EPDM)

Peroxide-initiated melt grafting of maleic anhydride (MAH) onto an ethylene–propylene–diene terpolymer (EPDM) of high ethylene content (=74 wt%) has been studied using a Brabender Plasticoder. The grafting efficiency and crosslinking degree (gel content) of the grafted EPDM rubber (EPDM-g-MAH) were determined by FTIR spectroscopy and xylene extraction, respectively. It was established that both grafting and crosslinking reactions are mostly influenced by the dosage of the MAH and peroxide (2,5-dimethyl-2,5-di-(t-butylperoxy)hexane), respectively. The targeted relative high MAH grafting at low gel content was reached at low concentrations of both MAH (<5 wt%) and peroxide (<0.2 wt%). Processing variables, as mixing temperature and time, rotor speed and filling grade of the mixing chamber, showed only a marginal effect on the competing grafting and crosslinking reactions.