Measurement and modeling of vinyl acetate polymerization kinetics to support new process development

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DuPont is developing a low temperature (<100 °C), low pressure (<100 bar) water-based miniemulsion process for the production of ethylene/vinyl acetate copolymers to replace the high temperature, high pressure (150-300 °C, 1500-3000 bar) technology used currently in industry. DuPont Canada is involved in the plans to scale-up the new process, with pilot plant design and development slated to begin in 2014. They have funded the Hutchinson group to study the underlying vinyl acetate radical polymerization mechanisms and provide accurate values of kinetic rate coefficients. The influence of head-to-head monomer insertion on polymerization propagation rate will be studied using a specialized pulsed-laser polymerization technique and NMR analysis of the resulting polymer structure, as well as measurement of the polymer molecular weight distributions. Using procedures previously developed for acrylate systems, the results will be analyzed to provide estimates for relevant propagation rate coefficients. A model of the polymerization kinetics, including degradative chain transfer and chain transfer to polymer, will be developed and verified against available literature data.