Early stages of thermo-oxidative aging of EPDM composites: Effect of aging temperature

The increasing generation of post-consumer rubber waste highlights the need to better understand aging mechanisms to develop more durable composites with extended service life. This study investigates the early stages of thermo-oxidative aging of ethylene-propylene-diene monomer (EPDM) composites and evaluates the effect of temperature on their mechanical, physicochemical, morphological, and thermal properties. EPDM composites with 40 phr of carbon black were processed on a two-roll mill and vulcanized at 160°C. Aging was conducted in an air-circulating oven at 70, 100, and 130°C for 168 h. Results indicate that crosslinking was the dominant mechanism at all temperatures, increasing molecular stiffness and reducing mechanical performance, with elongation at break decreasing by approximately 60%. Morphological analysis revealed degradation features such as cavities and microcracks. In contrast, thermal properties remained relatively stable, with glass transition temperature (Tg), onset degradation temperature (Tonset), and maximum degradation temperature (Tmax) ranging from −45 to −50°C, 435 to 452°C, and 456 to 473°C, respectively. FTIR analysis did not show the formation of typical degradation products, such as carbonyl groups. These findings demonstrate that significant degradation can occur even at 70°C within 168 h.