On the kinetics of emulsion copolymerization of methyl methacrylate and ethyl acrylate in the presence of hydrocarbons

Abstract

The emulsion copolymerization of methyl methacrylate with ethyl acrylate initiated by ammonium peroxodisulfate in the presence of a blend of anionic and non-ionic emulsifiers was investigated at 60°C. The polymerization under batch conditions was conducted to both low and high conversion. The kinetics of the emulsion copolymerization was studied in both the absence and the presence of diluents such as toluene and octane. Unexpectedly both diluents strongly reduced the rate of copolymerization. This reduction increased with increasing diluent concentration. The rate of polymerization was found to increase with increasing conversion up to high conversion. The average particle size increased very slightly with increasing concentration of the diluent. The average number of radicals per particle was found to increase with increasing conversion and to decrease with increasing diluent concentration. The decrease of the radical concentration with diluent concentration was attributed to the desorption of monomer radicals from a polymer particle and to the increase of the termination rate. It is proposed that the hydrophilicity of the monomeric radicals is the driving power of the desorption process.