Particle Size Distributions

Abstract

Particle sizes and particle size distributions are of both technical and scientific importance in emulsion polymerization systems On the technical side, particle sizes and particle size distributions are major determinants of a number of properties of a polymer latex, such as its viscoelastic behavior. Scientifically, experimental PSDs can furnish sensitive tests of mechanistic assumptions. Given the basic mechanisms and component rate parameters, particle size distributions (PSDs) can be predicted (as discussed in section 2 of this article). The problem is to find the values of those rate parameters. The major unknowns are those involved in particle formation, and for this reason part of this chapter examines the effect of nucleation on the PSD both experimentally and theoretically. While physically reasonable parameter values can be found which can reproduce experiment (e.g., the dependence of the particle number on initiator and surfactant concentrations, and the PSD during Interval I), such models are not yet reliably predictive. For cases where these rate coefficients have been established independently, calculations of the PSD in the absence of new particle formation give good accord with experiment. Moreover, appropriate comparison between theory and experimental PSDs can be used to infer kinetic information such as the size dependence of the entry rate coefficient.