NEW APPROACH FOR THE ESTIMATION OF KINETIC-PARAMETERS IN EMULSION POLYMERIZATION SYSTEMS .2. HOMOPOLYMERIZATION UNDER CONDITIONS WHERE (N)BAR GREATER-THAN 0.5

A new approach for the estimation of kinetic parameters in emulsion polymerization systems in which the average number of radicals per particle exceeds 0.5 is presented. The approach uses the time evolution of the conversion in chemically initiated systems and is based on a model that includes fundamental parameters such as the propagation rate constant, k(p), the termination rate constant in the polymer particles, k(t), the rate coefficient for initiator decomposition, k(I), and the entry, k(a), and exit, k(d), rate coefficients. It was found that k(p), k(t), k(I), k(a), and, under some circumstances, k(d) can be accurately estimated provided that termination in the aqueous phase is significant. When the extent of the aqueous phase termination is negligible, only k(p), k(t), and k(I) can be estimated. The effect of both the experimental noise level and the run-to-run irreproducibility on the accuracy of the estimates was studied. In addition, it was found that significant inaccuracies resulted from the poor determination of the exact time when polymerization begins. A method to circumvent this problem was proposed.