Control of multilayered core–shell dispersed particles in HPP/EPR/EbP blends and its influences on crystallization and dynamic mechanical behavior

According to a two-step preparation technique consisting of temperature-gradient extraction fractionation (TGEF) and subsequent solution-mixing, a series of polypropylene/ethylene-propylene random copolymer/ethylene-propylene block copolymer (HPP/EPR/EbP) blends containing multilayered core–shell dispersed particle with bridges were prepared to explore the influences of dispersed phase on crystallization and dynamic mechanical behavior. The inner core of the core–shell dispersed particles was mainly composed of EbP with long ethylene chain segment, and the intermediate layer was EPR and outer layer was EbP with long propylene chain segment. The size and layer thickness of the core–shell dispersed particle could be regulated by varying the ratio of EPR/EbP. With the decrease of EbP content, the outer interfacial thickness of core–shell structure decreases and the blends presented elevated melting points, which might be ascribed to enhanced nucleation ability. Meanwhile, the special simultaneous depression of glass-transition temperatures (Tg) of HPP and EPR was observed in all HPP/EPR/EbP blends compared with the Tgs of neat components, which was attributed to the enlarging free volume by imperfect co-crystals and infiltration of long ethylene chain segments of EbP component at interface.