Evolution of crosslinking networks structure and thermo-oxidative aging behavior of unfilled NR/BR blends with TBIR as extra functional compatibilizer

As the most popular rubber blends in rubber industry, the aging behaviors of NR/BR vulcanizates have been a major challenge in science and industry. Our previous work reported the substitution of trans-1,4-poly (isoprene-co-butadiene) (TBIR) for BR in filled NR/BR vulcanizates for improved thermo-oxidative resistance. However, the effect of microstructure, especially the evolution of crosslinking networks structure on aging mechanism of unfilled NR/BR blends with extra TBIR has not been studied cleanly so far. Herein, the relationship between the crosslinking structure and mechanical or dynamic properties for unfilled NR/BR blends with extra TBIR are showed, and the microstructure evolution before and after thermo-oxidative aging also has been discussed. The evolution of crosslinking network, compatibility and phase morphology are systematically investigated. The results show that the polysulfide bond content and density decreased with the increased thermo-oxidative aging time and increased with the TBIR content. The increased polysulfide bonds give NR/BR/TBIR blends excellent fatigue properties. The chemical structure and thermo-oxidative aging mechanism of NR/BR/TBIR vulcanizates are also been discussed.