Simulation model for the emulsion copolymerization of acrylonitrile and styrene in azeotropic composition

A simulation model based on the “unit segment” concept which provides prediction of conversion and molecular weight of product, is proposed for the emulsion polymerization of AN and St in azeotropic composition. Effects of initiator concentration and emulsifier concentration on conversion and molecular weight were studied experimentally and theoretically. It is found that the desorption of AN radicals should be taken into account, and the number of radicals per particle is always less than 0.5. The concentration of polymer particles is proportional to the 0.58 power in respect of the emulsifier concentration and to the 0.35 power in respect of the initiator concentration. The auto‐acceleration effect becomes significant when both initial emulsifier concentration and initiator concentration decrease, which influences the average molecular weight of the products. The azeotropic composition of AN–St is 28.5:71.5 by weight for this system at 60°C reaction temperature.