| Epoxy resin possesses strong adhesion and good chemical resistance due to its special molecular structure,as reasult of which it is widely used in coating field.Solvent of the traditional epoxy resin coating is so much that it pollutes environment and does harm to people’s health.Waterborne epoxy coating is green and convenient for construction.Thus waterborne epoxy coating has become a research hotspot.However waterborne epoxy coating is brittle and poorer than solvent-based epoxy coating in corrosion resistance.So it is necessary to modify waterborne epoxy to obtain composite coatings with excellent mechanical and anti-corrosion properties.The hydrophilic carboxyl groups（—COOH）were grafted to the macromolecular chain of epoxy resin to prepare waterborne epoxy emulsion through radical polymerization using bisphenol A epoxy resin E-20,methacrylic acid（MAA）,butyl acrylate（BA）and styrene（St）as raw materials.The synthetic resin was characterized and the effects of temperature,time,the dosage of monomer and initiator on the properties of modified resin and aqueous emulsion were discussed.The technological parameters and formula were determined.When the temperature was 100℃,the reaction time was 6h,the amount of methacrylic acid was 20%of the reactant mass,that of butyl acrylate was 10%,that of styrene was 7%,and the amount of initiator was 7%of the graft monomer,the waterborne epoxy emulsion had the best comprehensive performance.The silane coupling agent KH560 can enhance the compatibility between the fillers and the resin and make fillers disperse more evenly.The phosphoric hydroxyl of phosphoric acid can form strong chelating cooperation with the substrate and adhere to the surface of metal matrix in the form of covalent bond.In this paper,nanosilicon dioxide and graphene oxide were selected as modified fillers,and the nanoparticles were treated with KH560 and phosphoric acid to obtain modified nanosilicon dioxide and graphene oxide.Finally,the modified nanosilicon dioxide and graphene oxide were blended with the self-made waterborne epoxy emulsion,respectively,to study the influence of the content change of modified particles on the properties of the film,and the waterborne epoxy film with the addition of the untreated filler was compared.The study found that the modified filler had better dispersion in waterborne epoxy resin.,and it had certain resistance of water.When the solid content of waterborne epoxy emulsion is 50%,modified nanosilicon dioxide content was 2%of the waterborne epoxy emulsion,modified graphene oxide content was 1.5%,the composite film had the best comprehensive performance.In order to further improve the performance of waterborne epoxy coating,two kinds of fillers were mixed together to prepare the modified nanosilicon dioxide/modified graphene oxide/waterborne epoxy composite coating.The effects of the mixed fillers with different proportions and contents on the properties of the composite coating film were studied.The effects of the mixed fillers on the adhesion,hardness,impact toughness,water resistance,acid and alkaline resistance of the coating film were discussed.The research results showed that when the modified mixed filler content was 1%and the ratio was 1:1,high performance composite coating could be obtained.The adhesion of the coating film was grade 0,the hardness was up to 4H,the impact toughness was up to 60cm,the water resistance and acid and alkaline resistance was good,the electrochemical corrosion potential was 0.55V,the corrosion current was 5.12×10-10A which was smaller than the pure waterborne coating film by two orders of magnitude.The coating had better toughness and corrosion resistance than the waterborne coating modified by one kind of filler. |
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