Modeling Emulsion Polymerization of Vinyl Acetate: Redox Initiation Kinetics and Rigorous Phase Equilibrium Calculations with the PC-SAFT Equation of State

The behavior of oligoradicals, monomer partitioning, and aqueous phase kinetics still pose a significant challenge in emulsion polymerization modeling, due to their low experimental accessibility. On the other hand, mechanistic modeling can lead to an improved understanding of the aforementioned processes. In this work a kinetic polymerization model in the Predici (Polyreaction Distributions by Countable System Integration) software (Wulkow, M. PREDICI─A Software Package for Real-life Polymerisation Kinetics. In Progress in Industrial Mathematics at ECMI 94, Neunzert, H., Eds.; Vieweg+Teubner Verlag: Wiesbaden, 1996; pp. 166–175) is coupled with a PC-SAFT model to calculate phase equilibrium concentrations between kinetic time steps considering the aqueous, particle, droplet, and gaseous phases. The predicted system compositions are compared to the commonly utilized constant partition coefficients. Based on experimental data and literature research, a redox scheme for the system potassium persulfate (KPS), ascorbic acid (AsAc), and ferrous ammonium sulfate (FAS) is developed and utilized for kinetic simulations. To compare different approaches of chain-length- and solids-content-dependent termination rate and oligoradical diffusion modeling, the sensitivity of 2,2′-Azobis(isobutylamidine)dihydrochloride (AIBA)- and KPS-initiated emulsion polymerizations toward the aqueous phase is assessed. Subsequently, the ability to predict the experimental data of the developed redox scheme is compared to simplified schemes utilized in literature.