A Study of Microwave Radiation Effect in Devulcanization of Ethylene Propylene Diene Rubber Waste

The precise tuning of microwaves’ parameters during devulcanization of ethylene propylene diene (EPDM) waste can selectively break crosslinked network chains without degrading main chain. In this study, EPDM waste was pulverized into powder before being devulcanized to microwave radiation for 3 minutes at different power level (180, 300, 450, and 600 W). A Swelling test was conducted to measure soluble fractions and crosslink density to evaluate the degree of EPDM waste devulcanization. To elucidate the devulcanization quality, the Horikx theory approach was used, and Fourier transform infrared (FTIR) and thermogravimetric analyzes (TGA) were performed to study the devulcanized EPDM waste chemical interaction and degradation. Results reveal that the focus peak for the FTIR spectrum of the devulcanized EPDM (D-EPDM) was at S–S (556 cm−1), as exposure to microwave shows that the S–S bond intensity slightly increases. Moreover, D-EPDM 3 min/450 W shows low gel content % and crosslink density but a high in sol fraction. An increase in microwave radiation to 600 W results in a decrease in crosslink density and gel content but a high sol fraction where the random scission takes place, which shows a high degree of devulcanization percentage. Moreover, the thermal stability is lower for D-EPDM 3 min/450 W compared to grind EPDM (GEPDM sample (436.0 °C).