| A general kinetic model of particle formation in emulsion polymerization has been developed. This model takes into account homogeneous, micellar and monomer droplet nucleation mechanisms. Mechanisms which involve chain transfer and termination in the aqueous phase, capture of oligomer radicals by particles and coagulation of particles are also considered. The number of particles formed in batch emulsion polymerization over wide ranges of emulsifier and initiator concentration has been investigated by computer simulation with the mathematical model developed.; The critical chain length, n*, which is assumed to be the same for in-situ micellization nucleation or homogeneous nucleation, decreases with time during the very early stages in emulsifier-free systems. A two-stage model has been developed to simulate particle formation of emulsifier-free emulsion polymerization.; A new method was developed to determine the average number of radicals per particle, n, in emulsion polymerization. Solutions for n using this method have been obtained for a number of special cases and compared with other theories in the literature.; Experiments were carried out to investigate the influence of initiator concentration, monomer concentration, reaction temperature, agitator speed and chain transfer agent on the kinetic behavior of emulsifier-free emulsion polymerization of styrene using potassium persulfate as initiator. The presence of a small amount of a chain transfer agent such as carbon tetrabromide or mercaptans in the system increases the reaction rate. This unexpected behavior could be caused by a large number of precursor particles in dynamic equilibrium with the mature latex particles in the reacting system. |
