Emulsion polymerization: On the characterization of the particle size distribution

In emulsion polymerization, the polymer particles generated exhibit a size distribution. Broadness of the distribution is usually characterized by the uniformity (Dp), a ratio of weight to number average particle sizes, and is found to decrease with reaction time despite the fact that the particle volume distribution is usually broadened. Based on the mathematical model proposed by Lichti, Gilbert, and Napper, detailed analysis using the method of moment shows that standard deviation of the particle volume distribution increases with time, while that of the particle diameter distribution decreases with time. Dp's of both volume and diameter distributions all show decreasing with reaction time. These results are in agreement with those found experimentally. The present analysis indicates that, in the characterization of the broadness of the PSD in the emulsion polymerization, one has to be aware of the difference in meanings among these parameters related to the broadness of the PSD.