Kinetics and Polymer Microstructure of the Seeded Semibatch Emulsion Copolymerization of n-Butyl Acrylate and Styrene

The seeded semibatch emulsion polymerization of n-butyl acrylate, n-BA, with varying amounts of styrene as comonomer was investigated using potassium persulfate as initiator at 75 °C. The kinetics, the gel fraction, the molecular weight distribution, MWD, and the level of branches were determined. It was observed that the instantaneous conversion, the fraction of gel, the average molecular weights, and the level of branches were affected by the amount of styrene in the recipe. In particular, the fraction of gel decreased from 55% to almosnt nil and the level of branches decreased from 14 to 5 branches per 1000 carbons of the backbone when the amount of styrene increased from 0 to 10%. These results have technological implications because the amount of gel and the level of branches can be controlled; this is something that was not possible when initiator concentration or monomer feed rates were used as control variables. A mathematical model for predicting the kinetics, the fraction of gel, the level of branches and the MWD was used to analyze the effect of styrene on the seeded semibatch emulsion polymerization of n-BA. In addition, it is shown that the adhesive properties of these latexes can be modified by adding small amounts of styrene.