The design, synthesis, and study of novel vegetable oil macromonomers and their structure-property relationships in emulsion polymers
The coatings industry is continuously striving to reduction of volatile organic compounds in coatings. The Thames Research Group at The University of Southern Mississippi has devoted almost a decade to utilize vegetable oil macromonomers (VOMMs) in emulsion polymers and produce waterborne coatings that perform competitively with commercial coatings while containing very low levels of organic solvents. Soybean oil was acrylated to synthesize a monomer with an acrylate functionality of one, to avoid crosslinking during free-radical emulsion polymerization. The theoretical structure utilized a diglyceride species instead of the customary triglyceride. The diglyceride was acrylated through the hydroxyl functionality utilizing isophorone diisocyanate and 2-hydroxyethyl acrylate. The acrylation process builds a multifunctional monomer that contains one acrylate, two urethane linkages, two C-18 fatty acid chains, and an average of three double bonds per monomer unit. The entire synthetic procedure is a solvent-free process. Monomers were synthesized using four different vegetable oils, i.e., The varying concentrations of double bonds in these oils enabled the synthesis of VOMMs with different unsaturation levels. The VOMMS were copolymerized along with conventional monomers via emulsion polymerization to develop structure-property relationships necessary for optimizing the polymerization process. Property enhancements were evident with the ULiAM monomer. Upon ambient cure ULiAM-based latex polymers exhibited increases in gel content as high as 75% and increases in MEK resistance as great as 120 MEK double rubs. Oxidative crosslinking was further evidenced by the ULiAM-based latexes exhibiting Tg increases as great as 7.4°C and tan δ increases as great as 7.0°C. ULiAM-based coatings exhibited similar trends upon ambient cure with improvement in block resistance, MEK resistance, and scrub resistance. UCoAM and USfAM-based latexes exhibited limited improvements in properties with ambient cure due to the low concentrations of double bonds, while USAM exhibited moderate improvements in both latex and coatings properties.