Investigation of stabilization and kinetics in the semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate using carboxylic monomers

This work investigates the influence of carboxylic monomers such as acrylic acid (AA) and methacrylic acid (MAA) on the reaction rate and the colloidal stability during semicontinuous vinyl acetate (VA) and butyl acrylate (BA) emulsion copolymerizations. A number of copolymerization runs was carried out under different reaction temperatures and concentrations of AA and MAA. Samples were collected for off-line analysis of particle size and conversion, allowing calculations of particle number values giving an indication of the particle stability. Additionally, partitioning analysis using conductometric and potentiometric titrations were performed in order to assess the distribution of carboxylic monomers among the main phases of the latex. Results showed that for both carboxylic monomers the increasing of the reaction temperature produces an increase in the coalescence rate and that the increasing of the concentration of these monomers leads to the increase in the amount of adsorbed COOH groups on the particle surface, which enhances latex stability. Nevertheless, when the concentration of methacrylic acid was increased a strong reduction of the polymerization rate was observed with a greater incorporation of acid groups buried in the particles.