Abstract
The polymerization of vinyl acetate (VAc) in aqueous emulsions with an anionic emulsifying agent (Rapisol, Sodium dialkyl sulfosuccinate) and potassium persulfate (KPS) as an initiator was carried out in a water-bath (temperature range, 65-80). Time-conversion and time-temperature curves were measured, and the latter was found to consist of a plateau region and a peak. In the plateau region the polymerization proceeded under reflux of VAc-H2O azeotrope mixture. After the reflux ceased at 50-65% of monomer-conversion, the temperature in the flask rose remarkably and reached a maximum.
Assuming that the reflux occurs only in the plateau region, the temperature in the flask was calculated from the following data: heat of polymerization, polymerization rate, heat transfer from reaction system to water phase in the water-bath, rate of and latent heat of vaporization for VAc-H2O azeotrope mixture, heat capacity of the reaction system, and heating the azeotrope mixture. A satisfactory agreement of the calculated value with the observed one indicates that the effect of the reflux on time-temperature curve is significant. The influences of KPS concentration and water-bath temperature on the time-temperature curve are also discussed.
