Abstract

This study explores the impact of carbon black on the structure-property relationships of natural rubber during thermo-oxidative ageing. Natural rubber samples containing 27% mass of carbon black were subjected to ageing in air at temperatures ranging from 70 °C to 115 °C for up to 270 days. The ageing process was monitored in terms of oxygen consumption, swelling, and tensile testing. Results revealed a substantial reduction in crosslink density, highlighting chain scission as the dominant process. Tensile properties were significantly affected, showing decreases in modulus, elongation at break, and stress at break. A comparison with previous studies on unfilled natural rubber shed light on the role of carbon black during oxidation. Our findings suggest that carbon black plays a minor role in macromolecular network modifications for similar exposure conditions. More specifically, we analyze the validity of structure–property relationships between the average crosslink density and mechanical properties during thermo-oxidative ageing regardless of whether the elastomer contains carbon black filler. These results illustrate a new strategy for studying the aging of filled elastomers.