Kinetics of emulsifier‐free emulsion polymerization of styrene

The influence of initiator concentration, monomer/water ratio, reaction temperature, and agitator speed on the kinetic behavior of emulsifier‐free emulsion polymerization of styrene with potassium persulfate initiator has been investigated. Polymerization rate and the particle number increased with increasing initiator concentration and reaction temperature. The particle size distribution became broader as the initiator concentration decreased. Monomer conversion, at a common time, was smaller when the initial monomer/water ratio was increased. Particle size, at the same conversion, increased with an increasing initial monomer charge. High agitator speed caused significant particle coagulation. As a result, a smaller number of larger particles with broad size distribution were produced when the agitation was intense. Reaction rate decreased with increasing agitator speed. The two‐stage model developed in this paper can describe the kinetics of emulsifier‐free emulsion polymerization of styrene when potassium persulfate is used as initiator. Values of the termination rate constant, k tp , obtained from fitting the model to the experimental data are in agreement with k tp data reported in the literature for emulsion polymerization. k tp increases with increasing agitator speed because of a reduced gel effect. The rate coefficient for particle coagulation, K f , increases with decreasing initiator concentration, with decreasing reaction temperature and with increasing agitator speed. The rate coefficient for radical capture by particles, k c , increases with increasing reaction temperature and with increasing agitator speed.