Mechanochemical devulcanization ofEPDMrubber waste. Correlation of process parameters with sol–gel analyses and revulcanization properties

Abstract

AbstractEthylene–propylene–diene rubber (EPDM) scrap was devulcanized in an internal mixer with varying amounts of dibenzamido diphenyl disulfide (DBD) at temperatures below 200°C. The devulcanization effect and sol–gel analyses of the devulcanizates, and the mechanical properties of the sulfur‐cured revulcanizates were studied. Residual DBD was still present in the sol at 160°C and degraded DBD at 200°C. DBD affects the curing leading to poor properties. So, the temperature must be adjusted according to the DBD concentration to obtain a superior recyclate for sealing systems. At 0.4 wt% DBD, the degradation reaction was already complete at 120°C, but only 52% and 61% of the tensile strengthσand strain at breakεof the virgin material were achieved. At 160°C and 2 wt%, the degradation reaction was complete, and the DBD effect on properties was small; 65% and 86% ofσandεwere recovered, respectively. To prevent property degradation, 200°C was required at 3.9 wt% DBD, resulting in 97% and 95% ofσandε, but only 70% of hardness.