Regulation of trans‐1,4‐polyisoprene crystallinity and mechanical properties of styrene‐butadiene rubber/trans‐1,4‐polyisoprene vulcanizate

The effects of processing temperature and bis‐[ γ ‐(triethoxysilyl)‐propyl]‐tetrasulfide (Si69) on crystallization, morphology, and mechanical properties of styrene‐butadiene rubber (SBR)/trans‐1,4‐polyisoprene (TPI) vulcanizate are investigated. The crystallinity and crystalline melting temperature ( T m ) of TPI in the vulcanizates with TPI/silica/(Si69) pre‐mixed at 150 °C are much lower than that pre‐mixed at 80 °C. At the same pre‐mixing temperature, the presence of 1 phr Si69 leads to a decreased crystallinity and T m . The TPI domains with phase size of about 1 μm and silica are well dispersed in the vulcanizate, and TPI crystals get smaller in size and less in amount by pre‐mixing TPI, silica and Si69 at 150 °C. The vulcanizates with TPI/silica/(Si69) pre‐mixed at 150 °C have decreased tensile strength and modulus at a given extension than that pre‐mixed at 80 °C. At the same pre‐mixing temperature, the tensile strength and modulus of the vulcanizate increase with the addition of 1 phr Si69. The crystallinity of TPI component in SBR/TPI vulcanizate is effectively controlled by changing processing temperature and adding Si69, which is important for theoretical research and practical application of TPI. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44395.