ABSTRACT
We explore the impact of carbon black on the structure–property relationships of natural rubber (NR) during thermo-oxidative aging. NR samples containing 27% mass of carbon black were subjected to aging in air at temperatures ranging from 70 to 115 °C for up to 270 days. The aging 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 NR 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 aging regardless of whether the elastomer contains carbon black filler. These results illustrate a new strategy for studying the aging of filled elastomers.
Carbon black does not affect macromolecular network changes during the thermo-oxidative aging of natural rubber.
Coupling the Medalia equation and classical rubber elasticity theory accurately captures changes in the modulus of carbon black–filled natural rubber.
Decrease in elongation at break is effectively described by established structure–property relationships.
Filler–matrix interactions remain unaffected by oxidation.