Kinetics of semibatch emulsion polymerization of butyl acrylate stabilized by a reactive surfactant

The monomer feed rate (R-a) is the predominant parameter for controlling the rate of polymerization (R-p) in the semibatch emulsion polymerization of butyl acrylate (BA) stabilized by a reactive surfactant, sodium dodecyl allyl sulfosuccinate (SDAS). An induction period or even a complete inhibition of the polymer reaction observed for the experiments with relatively high SDAS concentration ([SDAS]) or low initiator concentration ([I]) is attributed to intensive chain transfer of the BA radicals to SDAS. R-p increases with increasing [I], whereas, it is relatively insensitive to changes in [SDAS]. The chain transfer agent, dodecyl mercaptan (DM) or carbon bromotrichloride (CBTC), was incorporated into the monomer feed to enhance the chain transfer reaction. The consumption of DM is diffusion limited because the relatively water-insoluble DM molecules have difficulties to diffuse from the monomer droplets to the reaction loci (latex particles) and, hence, it does not show a significant effect on the reaction kinetics. On the other hand, addition of CBTC with a higher water solubility to the reaction mixture reduces R-p significantly. When R-a decreases from 6.24 to 1.04 g/min, even the reaction kinetics of the system containing CBTC becomes monomer feed rate-controlled.