SURFACTANT EFFECTS IN THE EMULSION POLYMERIZATION OF VINYL-ACETATE

Continuous vinyl acetate emulsion polymerization was carried out by using a mixed surfactant system of “Aerosol” OT (AOT) and sodium dodecyl sulfate (SDS). It is well known that the AOT reduces surface tension considerably and has stronger monomer solubilization power than SDS. In this work, particular attention is given to observe the effects of the mixed surfactant on the molecular weights and polydispersities. In comparison with experiments using only SDS, the particle size appears similar, in the range of 190–280 nm. The conversion increased substantially to the 70% range from the 50% level observed with only SDS. All experiments were conducted at 60°C with a mean residence time of 30 min. The total surfactant concentration was maintained at 0.03 mol/L water for all experiments. It was found that once some AOT was included in the surfactant, the behavior was very similar to that observed with only AOT. The number average molecular weights were found to decrease substantially while the polydispersity increases dramatically to about 12. It is believed that AOT may act as a significant chain transfer agent in the polymerization. Copyright © 1990 John Wiley & Sons, Inc.