Aging behaviors of trans-1, 4-poly (isoprene-co-butadiene) copolymer rubber

Trans-1, 4-poly (butadiene-co-isoprene) (TBIR) displays high trans-1, 4-configuration (>90%) and gradient multi-block chain structure with varied length of trans-1, 4-polyisoprene (TPI) blocks and is expected to be used in high-performance "green" rubber composites owing to excellent dynamic properties. However, the aging behavior of TBIR in comparison with other general rubbers are not clear. In this work, the aging behaviors of TBIR with ~20 mol% butadiene units under thermo-oxidation, thermo-shearing and complex processing conditions were investigated in comparison with that of natural rubber (NR) and cis-1, 4-polybutadiene (BR). The thermo-oxidative aging resulted in chain scissions accompanied with oxidation to form carbonyl groups. The elastic modulus (G') and complex viscosity (η*) of TBIR decreased obviously with prolonging time during thermo-shearing aging process. Furthermore, the stability of TBIR undergoing conventional sequential processing procedures including internal mixing, calendering (open mill mixing) and then compression-molding was also evaluated. In comparison with NR, TBIR presented better stability to resist thermo-shearing, thermo-oxidative and sequential processing procedures. After thermo-oxidative aging, TBIR exhibited excellent abrasion resistance and higher retention degree of mechanical properties. This work will give better understanding on the stability of TBIR with isoprene-isoprene sequences and butadiene-butadiene sequences under complex conditions as comparison with general rubber materials.