In the present work we develop a mathematical model for the coagulation of polymer particles in emulsion polymerization systems. The model considers a Brownian coagulation kernel and assumes that interactions between particles can be described through the DLVO theory, where the presence of a Stern layer is accounted for. The model is then compared with experimental data for the coagulation of monomer swollen polyvinyl acetate particles, carried on with three different seeds at various operating conditions, showing in all cases a satisfactory agreement.