Factors influencing the emulsion polymerization of clay-platelet-assisted styrene-acrylic copolymer latexes

Controlling the particle size of solid-particle-stabilized emulsion polymers is a challenge for coating applications where high-solid-content emulsion polymers are required. Clay-particle-stabilized styrene-acrylic copolymer emulsion was prepared by a seeded semibatch emulsion polymerization process. The effect of the concentrations of clay, peptizing agent, and methacrylic acid on the processing, final particle size, and coagulum of the emulsion polymer was studied. Dynamic light scattering (DLS), dynamic mechanical analysis, differential scanning calorimetry, and field-emission-gun scanning electron microscopy techniques were employed to characterize the emulsion polymers. The kinetics of polymerization were monitored based on the percentage solid conversion, and particle size (DLS) analysis suggested a homogeneous coagulative mechanism. The zeta potential of the polymer particles indicated good stability of the emulsion. A stable, coagulum-free, low particle size (similar to 300 nm) emulsion was prepared using clay platelets, and the polymer film exhibited improved thermal and mechanical properties that will make this type of emulsion polymer of great use for coating applications.