Strategy for the NR/BR blends with improved thermo-oxidative resistance

The blends based on natural rubber (NR) and cis-1, 4-polybutadiene rubber (BR) are the most popular materials in rubber industry. As is well-known, the rubber blends suffer thermo-oxidative aging during the service life. However, the problems, such as immiscibility, discrepant aging behaviors, uneven distribution of fillers in different phase, resulted in unsatisfying mechanical properties of the filled NR/BR vulcanizates, especially after thermo-oxidative aging. In this work, a novel reactive compatibilizer trans-1,4-poly (isoprene-co-butadiene) (TBIR) is introduced to resolve the above problems for improved thermo-oxidative resistance of NR/BR blends. The mechanical properties of the sulfur cured NR/BR/TBIR vulcanizates with carbon black as fillers before and after thermo-oxidative aging are analyzed. The SEM, TEM and DMA are used to characterize the phase structure, filler distribution and dynamic properties of the NR/BR/TBIR blends. The NR/BR/TBIR vulcanizates exhibit better physical mechanical properties than NR/BR vulcanizate during the thermo-oxidative aging processing. The total crosslinking density and polysulfide crosslinking density increase during the aging process for all vulcanizates. The DMA results show that the Tg of NR and BR become closer with the increasing in TBIR whenever before and after aging, indicating the TBIR improves the compatibility of NR and BR. The phase morphology observation shows the improved filler dispersion level and reduced filler aggregation before and after aging process. The performance improvement mechanism of the thermo-oxidative aging of NR/BR/TBIR blends is discussed.