Multifeed emulsion polymers: The effects of monomer feed sequence and the use of seed emulsion polymers

The core/shell concept of emulsion polymerization postulates particle formation during the reaction in such a way that macromolecules formed in the early stages of the reaction are in the core or center of the final particles and latter-formed macromolecules are located in a shell layer around the core. This paper describes work done on model hard/soft and soft/hard two-stage, emulsion polymer systems. Variables studied included seed levels, monomer type, monomer addition sequence, surfactant level, and initiator level. Emulsion optical densities were used as estimates of particles size. Minimum film formation temperatures (MFT) were correlated with the above variables. Ratio of seed polymer/added monomer and initiator levels were found to markedly affect MFT.