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 (E-a) of the degradation process were determined using the Flynn-Wall-Ozawa method. For conversions up to 0.10, the E-a values of the EPDM-r samples without oil decreased with an increase in the microwave exposure time. POLYM. ENG. SCI., 51:697-703,2011. (C) 2010 Society of Plastics Engineers