The Relevance of Multi-Injection and Temperature Profiles to Design Multi-Phase Reactive Processing of Polyolefins

For industrial-scale continuous free radical induced grafting of polyethylene, which involves the contact of a monomer- and polymer-rich phase, it is demonstrated that the functionalization selectivity and grafting density can be significantly improved (e.g., 100%) by considering multiple injection of monomer and/or a temperature profile. With parameters taken from literature, it is highlighted through simulations that step-wise addition of monomer allows to reduce the homopolymerization rate, and an increased temperature at the start of the reactive processing allows to increase the hydrogen abstraction rate, so that more potential grafting points can be generated. As this increased grafting density goes along with a lower reaction extent, a better process efficiency is obtained albeit at a lowering of the average chain length of the grafts and an increase of the crosslinking density. In any case, a broader span of polymer characteristics (e.g., ranges of grafting/crosslinking densities and functionalization yields) can be achieved by including variations in reactant addition and temperature profiles.