Fabrication of polypropylene blends with excellent low-temperature toughness and balanced toughness-rigidity by a combination of EPR and SEEPS

To overcome serious rigidity depression of rubber-toughened plastics and fabricate a rigidity-toughness balanced thermoplastic, a combination of styrene-[ethylene-(ethylene-propylene)]-styrene block copolymer (SEEPS) and ethylene-propylene rubber (EPR) was used to toughen polypropylene. The dynamic mechanical properties, crystallization and melting behavior, and mechanical properties of polypropylene (PP)/EPR/SEEPS blends were studied in detail. The results show that the combination of SEEPS and EPR can achieve the tremendous improvement of low-temperature toughness without significant strength and rigidity loss. Dynamic mechanical properties and phase morphology results demonstrate that there is a good interfacial strength and increased loss of compound rubber phase comprised of EPR component and EP domain of SEEPS. Compared with PP/EPR binary blends, although neither glass transition temperature (T-g) of the rubber phase nor T-g of PP matrix in PP/EPR/SEEPS blends decreases, the brittle-tough transition temperature (T-bd) of PP/EPR/SEEPS blends decreases, indicating that the increased interfacial interaction between PP matrix and compound rubber phase is also an effective approach to decrease T-bd of the blends so as to improve low-temperature toughness. The balance between rigidity and toughness of PP/EPR/SEEPS blends is ascribed to the synergistic effect of EPR and SEEPS on toughening PP. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45714.