Simultaneous cross-linking as a way to control physical growth of random ethylene-propylene copolymer during formation of high-impact polypropylene

Abstract

An effective chemistry for controlling the physical growth of random ethylene-propylene copolymer (EPR) during formation of high-impact polypropylene (hiPP), i.e., PP/EPR in-reactor alloy, is proposed, by prompting EPR chains to be simultaneously cross-linked right during its polymerization. A sufficient degree of cross-linking in EPR effectively prevents its fleeing away from the catalyst fragments and into the pore network of pre-formed PP particles during the late E/P copolymerization of hiPP process, thus transforming EPR's dispersion morphology in PP particles from segregated droplet aggregates with mobility to catalyst fragment-adhered discrete particles with stability. This research not only contributes to the understanding of particle growth mechanism of hiPP but also provides a promising strategy for continuing innovating as well as expanding the scope of the industrially important in-reactor alloy technology.