Study On Synthesis And Properties Of Siloxane-modified Grafted Water-borne Epoxy

This paper aims at developing a kind of epoxy aqueous dispersion with excellent stability and good chemical resistance.In this paper, according to the molecule design, a kind of modified resin which had both epoxy groups and hydrophilic groups was synthesized. In the radical graft copolymerization, the epoxy resin was used as matrix, and methyl acrylic, methyl methacrylate and styrene were used as graft monomers.Although epoxy-styrene-acrylic copolymer aqueous dispersion has some good properties, storage stability couldn't meet the performance requirements of industry application, because it has a lot of epoxy groups. Therefore, epoxy-styrene-acrylic system was modified by silioxane, by which epoxy groups can be decreased and Si-O- covalent bonds were introduced, the modified aqueous dispersion has excellent stability and self-cured performance. Because of formation of Si-O-Si bonds, the chemical resistance of the copolymer membrane was improved greatly.In order to find out the optimum reaction conditions, the effects of reaction conditions such as initiators, initiators concentration, the amount of monomers for grafting, the mass ratio of hydrophilicmonomer, the temperature of grafting, and neutralization reagent were studied. The particle size and distribution of dispersion were measured by dynamic light scattering, The particle morphology of dispersion was observed by TEM. The results showed that when the ratio of monomer/epoxy was 10:7.95 with 22.2% of MAA and 2% of siloxane, the epoxy aqueous dispersion with the most stable and the minimal particle size would be obtained. And the particle had a shape of anomalous spherical. FTIR, SEM and TGA were used to characterize the structure and property of the product. The results showed that it was by chemical reaction that the epoxy was modified with styrene-acyrlic and γ-aminopropyl methyl diethoxysilone(A-2100). Its microphase structure was formed before curing, The membrane had a fine microphase structure, and the size of microphase region was 0.2-0.5μm. At the same time it had a similar thermal stability to epoxy-styrene-acrylic copolymer, and the massloss was 5% at 181°C. And it had good chemical resistance. The viscosity of the dispersion had not been changed greatly after 180d. The storage time is longer than one year.