BUTYL ACRYLATE VINYL ACETATE COPOLYMER CATER SYNTHESIS USING ULTRASOUND AS AN INITIATOR/

The polymerization of oil-in-water (o/w) emulsions of monomeric specie s has been performed at 30 degrees C (+/- 5 degrees C) under ultrasoni c irradiation, in the absence of any added chemical initiators. Emulsi ons of butyl acrylate and vinyl acetate as well as emulsified mixtures of the two monomers have been reacted in this way, In all cases, the radicals formed as a result of the ultrasonic cavitation were sufficie nt to cause polymerization. Stable blue-white or white dispersions of polymer latex particles were obtained, The kinetics of the copolymeriz ation process were monitored. The data obtained here show that the pol ymerization rate depends strongly upon the monomer concentration disso lved in the aqueous phase and on its vapor pressure, The more volatile of the monomers examined, vinyl acetate, was seen to have a markedly lower polymerization rate at equivalent monomer concentrations when co mpared to the butyl acrylate. This was attributed to monomer evaporati on into the cavities formed by the ultrasound, causing a dampening of the cavitation process and hence a lower radical density, Data of part icle sizes and polymer molecular weights for the latex samples support this hypothesis. (C) 1996 Academic Press, Inc.