Preparation Of Nonionic Waterborne Epoxy Curing Agent And Study On The Anticorrosive Performance Of Paint Film

With the rapid development of my country’s industrial field,the anti-corrosion and safety issues of various steel structures have attracted increasing attention.In addition,with the intensification of environmental problems,solvent-based coatings with high pollution and high energy consumption have been banned,while water-based coatings use water as a diluent and low VOC content,which can effectively reduce environmental pollution and improve the safety of coating transportation and use.At present,the water-based epoxy resin technology is very mature,but the supporting epoxy curing agent water-based technology still needs to be improved.In this thesis,bisphenol A epoxy resin and hydrogenated bisphenol A epoxy resin were used as raw materials and modified by hydrophilization,hydrophilic groups and polyamine segments were introduced,and the modified epoxy resin was capped with a monoepoxy compound to obtain two curing agents.A certain amount of graphene oxide is added to the bisphenol A epoxy resin curing agent to increase its corrosion resistance,and then the corrosion resistance and mechanical properties of the paint film prepared with the water-based epoxy curing agent are tested.In the synthesis of corrosion-resistant bisphenol A waterborne epoxy resin curing agent,the epoxy resin is firstly hydrophilized and modified.The influence of the molecular weight of the epoxy resin,the molecular weight of polyethylene glycol（PEG）,the reaction time,the amount of catalyst and the method of joining catalyst were explored.It was found that epoxy resin E51 had better performance as a curing agent synthesized as a raw material,and the molecular weight of PEG was determined to be 600,and 0.15 wt%of boron trifluoride-ether was added in a dropwise manner to catalyze the reaction for 70-80 min to obtain modified epoxy resin.Subsequently,the influence of the amount of TETA,the amount of propylene glycol methyl ether,the type of capping agent and the capping rate on the performance of the curing agent were considered,and the effect of the amount of graphene oxide added on the performance of the curing agent was investigated.The optimal molar ratio of E51,PEG600,TETA and BGE was 1:0.5:1.2:1.12,and the end capping ratio was 80%.The optimum amount of BF₃-ether catalyst and PM co-solvent and reaction stabilizer were 0.15wt.%and40wt.%of epoxy resin respectively.The reaction was a pale yellow liquid with a moderate viscosity of 7210 m Pa·s and an amine value of 157 mg KOH/g.The optimal mass ratio of epoxy emulsion and curing agent was 1.8:1.The cured coating showed a pencil hardness of 3H,impact strength greater than 50 Kg·cm,flexibility of 1 mm and adhesion of 1 grade.It can be seen from the AC impedance spectroscopy that with the increase of the content of graphene oxide,the corrosion resistance of the paint film showed a trend of first strengthening and then weakening.When the amount of graphene oxide added was 0.02 wt.%,the corrosion resistance of the paint film was the best,and its impedance modulus was 1.5 orders of magnitude higher than that of the paint film without graphene oxide,and the corrosion resistance was significantly enhanced.In the synthesis process of the corrosion-resistant hydrogenated bisphenol A water-based epoxy resin curing agent,similarly,the epoxy resin was firstly modified to be hydrophilic,and the effect of process conditions such as reaction temperature,reaction time and catalyst dosage on the performance of the curing agent was explored.Furthermore,the effects of the amount of TETA,the structure of the blocking agent,the blocking ratio and the mass ratio of the mixture with the epoxy emulsion on the performance of the curing agent were investigated.The study found that when the molar ratio of hydrogenated bisphenol A epoxy resin EP4080E,PEG,TETA and blocking agent BGE is 1:0.5:1.2:1.12,and the amount of PM is 60 wt.%,the reaction was a pale yellow liquid with a moderate viscosity of 6543 m Pa·s and an amine value of 143 mg KOH/g.The optimal mass ratio of epoxy emulsion and curing agent was 4:1.The cured coating showed a pencil hardness of 2 H,impact strength greater than 50 Kg·cm,flexibility of 1 mm and adhesion of 2 grade.Compared with bisphenol A epoxy resin curing agent,it had better corrosion resistance,and the impedance modulus was increased by 1.5orders of magnitude.In order to further improve the hardness of the paint film of the hydrogenated bisphenol A epoxy resin curing agent and enhance the adhesion of the paint film,a blend of bisphenol A and hydrogenated bisphenol A epoxy resins was used in the paper.The study found that when the molar ratio of EP4080E to E51 was 3:1,the three-step modification reaction temperature and time were 35^oC,70 ^oC,70 ^oC and 50 min,2 h,1 h,and the amount of catalyst was 0.15wt.%.The cured coating showed a pencil hardness of 4 H,impact strength greater than 50Kg·cm,flexibility of 1 mm and adhesion of 2 grade,the impedance modulus was increased by 1.5 orders of magnitude and it had excellent corrosion resistance.This research will provide an important research foundation for the industrial application of waterborne epoxy coating curing agents.