Devulcanization of ethylene-propylene-diene polymer residues by microwave-Influence of the presence of paraffinic oil

Vulcanized rubbers are materials commonly used in various industrial applications. In this study, scraps of ethylene‐propylene‐diene rubber (EPDM‐r) from the automotive industry were submitted to different microwave exposure times (2–5 min). Samples of recycled rubber with (as received) and without (after extraction) paraffinic oil were analyzed. The devulcanized EPDM‐r was characterized by gel content, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The gel content indicated that the presence of paraffin oil in EPDM‐r affects the devulcanization process. The DSC analysis showed significant changes in the glass transition temperature (Tg). The Tg values for EPDM‐r decreased with an increase in the microwave exposure time. Furthermore, the presence of a thermal phenomenon characteristic of uncured material was observed. Sample degradation was studied through TGA, and the values for the activation energy (Ea) of the degradation process were determined using the Flynn‐Wall‐Ozawa method. For conversions up to 0.10, the Ea values of the EPDM‐r samples without oil decreased with an increase in the microwave exposure time. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers