Polyurethane Modified Waterborne Epoxy Resin And Its Application In Anticorrosive Coatings

Metal corrosion is widespread in transportation,oceans,buildings,and daily life.The global annual loss caused by metal corrosion is serious.Epoxy resin is widely used in metal anti-corrosion coatings due to its outstanding corrosion resistance.The common powder coatings and solvent-based anti-corrosion coatings.Powder coatings are difficult to construct and costly.Solvent-type anti-corrosion coatings commonly used on the surface of metal materials will not only pollute the environment,but also endanger human health.Therefore,from the perspective of controlling volatile organic compounds,this thesis uses physical blending and chemical copolymerization to prepare polyurethane-modified waterborne epoxy resin emulsions.The synthesized emulsions are formulated into water-based anticorrosive coatings to explore the basic properties of the coatings.The first chapter mainly introduces the corrosion mechanism and coating anti-corrosion principle,and four common water-based coatings,water-based inorganic zinc-rich anti-corrosion coatings,water-based acrylic anti-corrosion coatings,water-based polyurethane anti-corrosion coatings,and water-based epoxy resin anti-corrosion coatings.Focused on the related content of the water-based epoxy resin,including the structure and performance of the epoxy resin,the synthesis method of the water-based epoxy resin,several main methods of anti-corrosion modification and their related applications in anti-corrosion coatings.In the second chapter of this paper,a polyurethane-modified waterborne epoxy resin was prepared by a physical blending method,and a waterborne polyurethane(WPU)emulsion and a waterborne epoxy resin(WEP)emulsion were synthesized separately.The emulsion stability and particle size analysis showed that when n(E-44): n(A-95)=8:1 and R=1.8,the epoxy resin emulsion has good stability,and the stability is more than 6 months.The water-based polyurethane emulsion is added to the epoxy resin emulsion for physical blending.By adjusting the mass ratio of WEP and WPU,the effect of polyurethane content on the performance of the mixture is explored.When the mass ratio of WEP to WPU is 4/6,the adhesion of the coating film can reach level 0.The pencil hardness is 3 H and the impact resistance is 50 kg·cm.The water absorption rate of the composite film is 3.74%.The strength is 22.6 MPa.The tensile section morphology of the film shows that the addition of p olyurethane significantly improves the toughness of the epoxy resin.The third chapter of this article selects the epoxy resin prepolymer and polyurethane prepolymer,with the chain extender piperazine.Used the chemical copolymerization method to connect the polyurethane and epoxy resin segments to synthesize polyurethane-epoxy Resin block copolymer.By adjusting the quality of piperazine,the influence of chain extension Rt value on composite materials was explored.And the product has been tested by infrared,particle size,stretching,thermogravimetry and so on.The results show that the emulsion stability of the modified compound obtained after adding piperazine is more than 6months.The pencil hardness of the coating film is increased to 5 H and both reach the 0 level adhesion.The maximum tensile strength of the composite film can reach 33 MPa,the water absorption rate has also decreased.The heat resistance of the film has been improved compared with the cured product of the pure water-based epoxy resin WEP3.In the fourth chapter of this paper,the polyurethane-modified waterborne epoxy resin(PUCME1)is used as the matrix resin,and then titanium dioxide,barium sulfate,kaolin,and mica powder are used as different pigments and fillers to prepare four types of polyurethane-modified waterborne epoxy resins(PUCME1).Epoxy anticorrosive coating,and tested the adhesion,impact resistance,corrosion resistance and other properties of the coating film.The results show that the pencil hardness of the four coating films is above 4 H.The adhesion is above 0 grade,and the coating films have good water resistance.PUCMET1 and PUCMET4 have better acid and alkali resistance and salt spray resistance.The Tafel curve and EIS test show that PUCMET1 has the best corrosion resistance,which also shows that the coatings with mica powder as the filler have the best anti-corrosion effect.