| With the increasing awareness of environmental protection,the importance of environmental protection in various countries,and the restrictions on volatile organic compounds(VOC)emissions by relevant laws and regulations,environmentally friendly coatings have developed rapidly.Water-based epoxy coatings are becoming more and more popular due to that they are safe,environmentally friendly,and low VOC.As the core component of waterborne epoxy coatings,the performance of waterborne epoxy emulsions is directly related to the performance of waterborne epoxy coating products.However,the current waterborne epoxy emulsions on the market still have the disadvantages of poor storage stability and water resistance.Improving their performance is an urgent need in the market.Modification of waterborne epoxy emulsions to eliminate their defects and further improve their performance to reach or approach the level of solvent-based epoxy resins is an important research direction of waterborne epoxy resin modification.In this paper,we provided two strategies to achieve the modification of waterborne epoxy emulsion in order to obtain high performance waterborne epoxy emulsion.The first strategy is to improve the storage stability of waterborne epoxy emulsion by adding thickeners on the basis of the existing reverse conversion process.The second strategy is to introduce nano-scale graphene oxide to improve the stability and corrosion resistance during the preparation of waterborne epoxy emulsion.This method stabilizes the epoxy emulsion which is in thermodynamics unstable state through the introduction of nano-materials.With the assistance of these two strategies,we found the appropriate addition amount,which greatly improved the stability and corrosion resistance of waterborne epoxy emulsion,and improved the comprehensive properties of waterborne epoxy emulsion.The main research contents and conclusions are as follows:(1)Waterborne epoxy resin emulsion was prepared by the phase inversion method of emulsifier.The effects of the content and proportion of the compound emulsifier,the reaction temperature and the stirring speed on the stability of waterborne epoxy emulsion were investigated.The optimum technological conditions for the preparation of waterborne epoxy emulsion were optimized by orthogonal test:the emulsifier content was 9%,the emulsifier ratio was 1:13,the reaction temperature was 70?,and the stirring speed was 600 r/min.(2)The performance of the freshly prepared and expired waterborne epoxy resin emulsion was tested and characterized.The stability of the freshly prepared and expired waterborne epoxy resin emulsion and the anticorrosive properties of the coating were compared.It was found that both of the stability of the expired waterborne epoxy emulsion and the dielectric resistance of the coating decreased.(3)Waterborne epoxy emulsion was modified by inorganic thickening agent magnesium silicate lithium(Li2Mg2O9Si3)and organic polyurethane thickening agent RM-8W.The effects of these two thickeners on the properties of waterborne epoxy emulsion were compared.It was found that the addition of 3.3wt%thickener RM-8W can maximize the stability of waterborne epoxy resin emulsions,and also improve the dielectric resistance of waterborne epoxy coatings to a certain extent.At the same time,other properties of waterborne epoxy coating remain unchanged.(4)Graphene oxide(GO)was used to further modify waterborne epoxy emulsion.The effect of GO on the properties of waterborne epoxy emulsion was studied.It is found that the addition of 3.0wt%GO can not only improve the corrosion resistance of waterborne epoxy coating,but also improve the mechanical properties of waterborne epoxy coating.Therefore,the comprehensive performance of waterborne epoxy coating is improved effectively by the introduction of GO. |
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