KINETIC-STUDY OF THE MINI-EMULSION POLYMERIZATION OF STYRENE

A broad particle-szie distribution in mini-emulsion polymerization is generally attributed to the long induction period and homogeneous nucl eation in the aqueous phase. In this study, the high dissociation rate of the interfacial redox initiator system cumene hydroperoxide/ferrou s ion/ethylenediaminetetraacetic acid/sodium formaldehyde sulfoxylate (CHP-Fe2+-EDTA-SFS), which could produce hydrophobic radicals and decr ease homogeneous nucleation in the aqueous phase, was used to prepare the mini-emulsion polymerization. Polystyrene particles of narrow size distribution were obtained, and their molecular weights were also ver y narrow (polydispersity index = 1.5-2.0). The effects of the initiato r concentration, the ratio of surfactant/cosurfactant (sodium lauryl s ulfate/cetyl alcohol, SLS/CA), the styrene concentration and the react ion temperature in the mini-emulsion polymerization of styrene were al so investigated. When higher or higher reaction temperature were used in the mini-emulsion polymerization, the polymerization rate and conve rsion became higher. The order of SLS:CA ratios for preparing polymer particles of high stability was 1:3 > 1:10 > 1:1 > 1:6 > 1:0. (C) 1996 Elsevier Science Ltd.