| Epoxy resins are widely used in anti-corrosion coatings and other products due to their excellent physical and chemical properties.However,because of lipophilic and hydrophobic properties,they can only be dissolved or dispersed in organic solvents.A large amount of volatile solvents will cause environmental pollution and influence human body health,so it is particularly important to develop water-based epoxy resin.However,in the process of water-based epoxy coatings which used in metal anti-corrosion,there are still many problems to be settled in terms of performance and coating.Therefore,research and modification of the anti-corrosion performance of water-based epoxy resins have important practical significance and industrial application prospects.In this study,MHHPA,PEG-2000 and EP-44 are used as raw materials.First,MHHPA and PEG-2000 are subjected to an esterification chain extension at a molar ratio of 2:1 to form prepolymer A,and put in 2 times its molar EP-44.The two undergo ring-opening reaction of epoxy groups to generate water-based epoxy emulsifier,the HLB value is measured to be about15,which meets the requirements of the emulsifier for water-based epoxy resin prepared by the reverse conversion method.EP-44 was emulsified with synthetic water-based epoxy emulsifier and reverse conversion technology to prepare water-based epoxy resin.The effect of the process conditions of the emulsification process on the particle size and stability of the emulsion was studied and optimized.When the content is 16%,the temperature is 60?65?,the stirring rate is 3500 r/min,the time is controlled at 35min,the prepared aqueous epoxy resin has a solid content of 50%,a viscosity of 5668 m Pa s,a particle size of 326 nm,and excellent stability,p H7 and epoxy equivalent of about 782 g·mol-1.The curing agent BANCO 905 was cured and cross-linked with it.The resulting epoxy coating had a hardness of 2 H,flexibility of 1 mm,adhesion of 0 grade,60°gloss of 102.8,impact strength of 86 cm,good acid and alkali resistance and water resistance.Glass transition temperature 65.3?,contact angle 85.6°.Using EP-44 and H3PO4 as monomers,the epoxy ring-opening reaction is carried out according to the ratio of epoxy group to hydroxyl group 3:2,to generate water-based epoxy phosphate,which is neutralized with weak base to prepare milky white water-based epoxy phosphate Lotion.Using the?-?interaction between its molecular structure and graphene,a stable and uniform graphene dispersion was prepared.The effect of solid content and graphene content on dispersion stability was studied.When the graphene content is 3.5 mg/m L,the viscosity of the prepared graphene dispersion?25??is 1672 m Pa s,the centrifugal stability can reach level 4,it can be stored stably for more than 1 month at room temperature,the p H is 7,graphene can exist stably in a few layers.The prepared graphene dispersion is mixed with water-based epoxy resin,and other additives are added to prepare an anti-corrosion coating.Using the electrochemical polarization curve as a characterization method,the effect of graphene content on the corrosion resistance of the composite coating was studied.When the graphene content is 0.5%,the graphene modified composite coating has improved salt spray resistance compared with the epoxy coating 16.7%,the corrosion resistance efficiency increased by 7.6%,and the mechanism of graphene to improve the corrosion resistance of epoxy coatings was analyzed and discussed by the perspective of microstructure and interface chemistry.In addition,the thermal stability of the composite coating has also improved,with the glass transition temperature increased by11.3%and the thermal decomposition temperature increased by 7.7%. |
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