Latex stability in semibatch surfactant-free seeded emulsion polymerization of butyl acrylate

The seeded technique was used to study particle growth mechanisms involved in semibatch surfactant-free emulsion polymerization of butyl acrylate (BA) in ordr to avoid complicated effects by particle nucleation. The data show that limited flocculation, often observed in the polymerization system containing no seed particles, did not occur in this work. This is attributed to the extensive formation of coagulum during polymerization. Agitation speed is the most important variable in determining the amount of total scrap produced, followed by initiator concentration, monomer feed rate, and then buffer concentration. A carboxylic seed latex was prepared to further study particle growth mechanisms. The level of coagulum for these runs using a carboxylic seed latex is much lower than that for the runs using an ordinary poly(butyl acrylate) seed latex. Limited flocculation was not observed during the reaction. In this case, nucleation of a second crop of primary particles during monomer addition was confirmed.