Mathematical modeling of the catalytic degradation of polystyrene in the presence of aluminum chloride

Abstract

We model the effect of the catalyst AlCl3 on polystyrene (PS). Detailed experimental studies were previously carried out on the effect of AlCl3 on PS, as part of an effort to understand how to minimize the degradation of PS during the Friedel–Crafts alkylation performed to obtain a graft copolymer from immiscible blends of PS and a polyolefin (PO). In the present work three mathematical models for the catalytic degradation of PS are proposed, all of which consider that reaction starts with the elimination of a phenyl group from the PS chain, followed by either chain scission or a change in the chain structure. The models vary in the way they consider the strength of the main chain bonds, or the reactivity of modified PS chains. Kinetic parameters for each model are estimated. Although the three proposed models could be used to represent our own experimental data, one is more accurate. Experimental data from other authors are used to evaluate its capabilities. Based on the predictions of the better model, we discuss conditions to minimize PS scission, such as operating at low temperatures and AlCl3 concentrations, and using short processing times.