| Because of the special properties, such as excellent bonding, electrical insulation, mechanical properties, corrosion resistance, etc, epoxy resin has been applied in many important fields. However, due to the poor heat and impact resistances, the application scope is largely limited. In order to improve its properties, the epoxy resin could be modified by chemical methods, especially the modification of thermal stability and water solubility. With the advantages of innocuity, insipidity and pollution free, the waterborne paint, as an environment-friendly coating product has been applied widely and developed greatly.Epoxy resin E-44 was modified with silica sol. By introducing silicon sol into the epoxy resin E-44 molecules, a cross-linked with the appropriate network system was formed, and this could reduce the internal stress and increase the other properties, such as tenacity and heat resistance. Silica sol was prepared from TEOS hydrolysis and both orthogonal experiment and single-factor experiment were used. From the experiments, the optimized modified conditions of the preparation of silicon sol were as follows:the mole ratios of water and TEOS, EtOH and TEOS, and Hydrochloric acid and TEOS were 3:1,6:1, and 0.07:1, respectively; and the process was first hydrolyzed at 30℃for 1 h, and then kept the temperature at 50℃for 40 minutes. The optimized conditions of the modification were as follows:the mass ration of silica sol and epoxy resin E-44 was 5:3, the amount of catalyst was 2.5%, and the reaction was carried out at 65℃for 2 h.The zinc-rich anti-corrosion coating was prepared by the modified epoxy resin-based material. Coating properties were studied, and electrochemical impedance spectroscopy (EIS) was employed to investigate the corrosion regulations of modified epoxy coatings on carbon steel in 3.5 mass% NaCl solution. The following results were obtained.1) The silica sol could improve the anti-corrosion performance of the coatings effectively, and the optimal condition was that the mass ration of silica sol and epoxy resin E-44 was 5:3. The coating showed excellent mechanical properties, heat resistance and weatherability resistance.2) According to the EIS characteristics, the entire deterioration processes could be divided into three main stages:water seepage, base metal corrosion, coating failure and the corrosion of the base metal. As the coating resistance decreased with time, the protective function reduced with the coating degradation.3) The reaction between Silicon sol and epoxy resin E-44 could increase the chemical and physical crosslinking points in the modified products. Besides, during the process, part of the micro-pores on coating could be filled, and then the coating density and hydrophobic properties were improved.In order to investigate the properties of waterborne epoxy resin, the epoxy resin was modified by a chemical method. First, hydrophilic groups were introduced to the epoxy resin by diethanolameine to obtain a rational balance point between the hydrophilic property and the reaction activity. Then, acetic acid salt was added in order to disperse the E-44 epoxy resin to form a stable aqueous system. The influences of reaction temperature, reaction time, reactants amount ratio and water amount on epoxy resin aqueous system were studied. The following results were obtained.1) The appropriate modified conditions were as follows:with ethyl acetate as the solvent, the mass ration of diethanol amine and epoxy resin E-44 was 1:4, and the reaction was carried out at 80℃for 3 h.2) With various ratios of water, the modified E-44 epoxy resin could be in the form of aqueous solution and water emulsion. The color of the modified E-44 epoxy resin became deeper with time, so it is with the viscosity.3) In the zinc-rich water-based epoxy coatings, while the adding amount of waterborne epoxy resin was 40%, the coating possessed a good overall performance. However, comparing with the solvent-based epoxy zinc-rich coatings, there are still many improvements need to do. |
PDF Full Text Request