Oil–acrylate hybrid emulsions, mini-emulsion polymerization and characterization

Abstract

The use of oxidized triglycerides as initiators for the mini-emulsion polymerization of acrylate is described. Unsaturated triglycerides, as in, e.g. sunflower, were treated with molecular oxygen to generate fatty-acid hydroperoxide groups. Oil–acrylate hybrid emulsions were formed using the fatty-acid hydroperoxides as initiators for the mini-emulsion polymerization of acrylates in an Fe 2+/EDTA/SFS redox system. The mini-emulsion system was established with n-hexadecane as hydrophobe. The kinetics of the mini-emulsion polymerization and the characteristics of the particles were examined. Cryogenic transmission electron microscopy (cryo-TEM) analysis of the hybrid emulsions obtained by initiation with the fatty-acid hydroperoxides did not show intraparticle heterogeneity. Initiation by t-butyl hydroperoxide on the other hand resulted in the formation of heterogeneous particles as was found by cryo-TEM. This indicates that the use of fatty-acid hydroperoxides resulted in the formation of oil–acrylate copolymer which acted as a compatibilizer. It is concluded that the use of fatty-acid hydroperoxide-initiated mini-emulsion polymerization results in a promising system of combined alkyd–acrylate properties.