Evolution of the partition coefficients of peroxide initiators during the synthesis of high-impact polystyrene

Abstract

The partition coefficient K of commercially available peroxide initiators between polystyrene (PS) and polybutadiene (PB) phases during the synthesis of high-impact PS is investigated with model systems. Influences of styrene conversion and peroxide initiator concentration on K are studied for two different PBs. It is shown that K varies linearly with conversion, exhibits a logarithmic behaviour according to the peroxide initiator concentration, and is influenced by the microstructure of PB. Nevertheless, these effects are weak. For any peroxide initiator family studied, i.e., percarbonate, perester, and perdiketal, the values of K are close to 1, showing that peroxide initiators are evenly distributed between the PS and PB phases, before the phase inversion.