The effects of various monomer addition methods on the emulsion copolymerization of vinyl acetate and butyl acrylate

Various monomer addition methods were applied to the emulsion co-polymerization of vinyl acetate and butyl acrylate of which polymerization reactivities are very different from each other. The grafting efficiency and homogeneity of copolymer were determined by the fractionation and measurement of dynamic viscoelasticity of emulsion polymers. As the content of the second fraction of acetone-soluble part increased and that of the third fraction decreased, then the homogeneity of the copolymer increased, In this case, only one dynamic loss peak existed near 0°C. The result showed that homogeneous copolymers were obtained by continuous monomer addition methods and heterogeneous copolymers were obtained by initial addition of total monomers or stepwise monomer addition methods. Homogeneity of copolymer had great influence on various properties, e.g., hardness and adhesive properties. Film hardness was the lowest for homogeneous copolymer and it was the highest for heterogeneous copolymer. Homogeneous copolymer was best for adhering plywood and poly(vinyl chloride). It is remarkable that copolymers of vinyl acetate and butyl acrylate with very different properties were obtained by changing only the monomer addition methods.