Investigation On The Preparation And Performance Of Polyurea Crosslinking Modified Acrylate Elastic Emulsion

With the increasing awareness of environmental protection and much strictly environmental regulations, the aqueous coatings which have the characteristics of low pollution and low hazard, have became the protagonist of the world's coatings market in the 21st century, and widely used in construction, furniture, vehicles, and light industry. At present, it also has a large share in our country. The aqueous coatings prepared by the polyurethane / acrylic resin emulsion have been applied quite widely. However, the performance which need to improved and better ways to obtain the special features are still problems. It is well known that, polyurethane, polyurea and acrylate polymer can be complementary to each other in performance. Although there have been many reports on the synthesis of the polyurethane modified acrylic emulsion, the synthesis of polyurea cross-linking modified acrylic emulsion were rarely involved.The thesis has a comprehensive review on emulsion polymerization theory and film flexibility principle, Acrylic elastic emulsion research progress, polyurethane (polyurea) modified acrylate elastic emulsion research progress.The preparation of the polyurea modified acrylic emulsion and many influencing factors were explored and studied in the thesis. To compare polyurea cross-linking modified acrylic latex (PUA) with acrylic emulsion (PA) in the aspect of performance. End isocyanate polyurea prepolymer is synthesized by amino-terminated polyethers with toluene diisocyanate using acetone as the solvent. Due to the reversible condensation reaction of amine and acetone, the activity of the amino groups and isocyanate groups was reduced. Thus the reaction rate could be better controlled and the ratio of adverse reactions would be decreased. The PU macromonomer which contains two double-bonds was obtained through polyurea prepolymer which was terminated by the double-bond of hydroxyethyl acrylate ester. It was further used as the cross-linking agent and combined with methyl methacrylate, butyl acrylate; finally, the acrylic latex elastic which was modified by PU was synthesized by emulsion copolymerization. The films were characterized by FTIR, DSC and TGA measurement. Furthermore, the best synthetic process, the suitable experimental conditions and many other factors were determined.This thesis show that, comparing with acrylic emulsion, the acrylate elastic emulsion, which modified by polyure, have better mechanical poperties, low temperature resistance, thermal stability and solvent resistance. In addition, in the thesis, the existing problems in the experiment were discussed and the next stage of the study are described.