Free Radical Polymerization studies of vinyl ester monomers using Pulsed-Lased Polymerization with Size Exclusion Chromatography (PLP-SEC)
MetadataShow full item record
Polyvinyl acetate and other polyvinyl esters, and their copolymers are used in coatings, adhesives and plastics, and hence fundamental understanding of the mechanisms and polymerization kinetics is vital for process development, and production of existing and new polymer grades in an effective and safe manner. The propagation kinetics of radical homopolymerization (bulk) of vinyl acetate (VAc), vinyl pivalate (VPi) and vinyl benzoate (VBz) was studied using Pulsed-Laser Polymerization coupled with Size Exclusion Chromatography (PLP-SEC) at laser pulse repetition rate (prr) between 2 and 500 Hz, and the temperature range of 25 - 90 °C. The propagation rate coefficient, kp, determined for VAc and VPi increases significantly with prr (20 % between 200 and 500 Hz prr), with the kp value for VPi ~50 % higher than that of VAc. This significant increase in kp with prr has been explained by the head-to-head addition defects that occur during vinyl ester polymerizations. For VBz, no kp value was reported due to lack of PLP-structure, likely due to resonance stabilization of the radical. Solution polymerization of VAc and VPi was also studied by PLP-SEC using ethyl acetate (EAc) and heptane (50 % by volume) at 50 °C, with the kp values having no substantial solvent effect. The polymerization kinetics of these vinyl ester monomers were also investigated using small-scale batch polymerization at 60 °C both in bulk and in solution (using EAc). The monomer conversion profiles obtained showed the same pattern in both bulk and solution, with the rate of conversion faster for VAc than VBz, and VPi even faster, trends consistent with the kp values determined using PLP-SEC. Kinetic models were implemented in the Predici software package, and are shown to fit the experimental batch polymerization data reasonably well.