Some Factors Affecting the Molecular Weight Distribution (MWD) in Low Density Polyethylene Multizone Autoclave Polymerization Reactors

Abstract

Due to its complexity, free-radical polymerization of ethylene at high pressure still remains to be fully understood. This paper investigates factors that contribute to shape the MWD, one of the main features of LDPE, such as the structure of primary chains and the reactor operation in one/two phases. Using plant data and different models, it is found that chain transfer to small species is the controlling chain termination step and it is explained why one-phase operation leads to more branched polymer. Simulations with the Polyred software package provide a set of kinetic parameters that reproduce the observed trends in number average molecular weight and MWD dispersity in the reactor.