In situ reactive compatibilization of polypropylene/trans-1,4-poly(isoprene-co-butadiene) rubber (TBIR) blends with balanced toughness and stiffness via dynamic vulcanization

Toughening polypropylene (PP) with the good balance of toughness and stiffness was achieved via dynamic vulcanization technology by blending with trans-1,4-poly(isoprene-co-butadiene) rubber (TBIR), a novel copolymer containing trans-polyisoprene blocks with glass transition temperature (Tg) around -70 degrees C and melting temperature (Tm) around 25-45 degrees C. Dynamically vulcanized PP/TBIR blends (PP/TBIR DV blends) using sulfur as crosslinking agent was prepared and the phase morphology, glass transition temperature (Tg), crystalline behaviors and mechanical properties of the PP/TBIR DV blends were investigated in details. The PP/TBIR DV blends with 20-25phr TBIR incorporation presented outstanding notched Izod impact strength (12 times higher than that of pure PP) and a high-level tensile strength (about 24 MPa). The TBIR rubber phase was dispersed uniformly in the PP/TBIR DV blends with domain size around 500 nm, and was showed little change with an increase of TBIR content. DMA results demonstrated that the dynamic vulcanization crosslinking enhanced the interface compatibility between PP and TBIR through the increased Tg of both TBIR and PP domains, in which TBIR domains presented more influence. WAXD results showed that the crystallinity of PP decreased slightly, while the crystallinity of TBIR was reduced by 50%. The evolution of morphology and compatibility of the PP/TBIR DV blends were investigated and discussed in detail. Dynamic vulcanization under the optimum curing reaction time definitely hindered the coalescent of the TBIR particle due to the decreased particle adhesion. The co-crosslinking of TBIR and PP caused by dynamic vulcanization improved the compatibility between PP and TBIR obviously.