Microemulsion polymerization of butyl acrylate under ultrasound irradiation

Abstract

The microemulsion polymerization (MEP) of butyl acrylate (BA) stabilized by ionic emulsifier and initiated by oil-soluble dibenzoyl peroxide (DBP) or lauroyl peroxide (LPO) initiators have been studied under conventional (without ultrasound irradiation, CMEP) and ultrasonic (NMEP) conditions. The polymerization rate vs. conversion curve of the microemulsion polymerization of BA initiated by DBP was described by two nonstationary rate intervals. Four nonstationary rate intervals with two rate maxima appear in the microemulsion polymerization of BA initiated by LPO. The maximal rate of polymerization increases with temperature and the increase is much more pronounced under the conventional conditions. The overall activation energy is much larger under the conventional conditions (= 84 kJ·mol-1) than under the ultrasound (= 20 kJ·mol-1) conditions. The exit (desorption) rate constants k′des (cm2 s-1) and k des (s-1) (Ugelstadt/O'Tool approach. Nomura model and Gilbert model) as a function of temperature and the initiator type and concentration for the CMEP and NMEP were evaluated. Generally, the k′,des (cm2 s-1) slightly increase with increasing the reaction temperature (except for the highest and lowest temperatures estimated by Tmodel). The values of kdes (s-1) and k′des (cm2 s-1) are larger under the ultrasound conditions. The increased degradation of micellar aggregates by ultrasound irradiation is in favour of the desorption of monomeric radicals.