Study On Organic-inorganic Hybrid Epoxy Resin Coating

Bisphenol-A epoxy resin, which has been known as a general resin, is the most frequently produced and used epoxy resin. The resin can get many advantages after cured, such as high adhesive strength, strong erosion resistance and good electric property. However, there are also many shortcomings, such as low toughness and poor weatherability, which restricts its application. These properties can be improved by organic/inorganic hybrid modification though Sol-Gel techniques.In this study, a kind of modified silica sol was synthesized by tetraethoxysilanes (TEOS) and silane coupling agent (using KH-560 in this study), using sol-gel method. The influences of different pH values, temperature and proportions of reactants on the conversion of modified silica sol were investigated. Finally, the optimal reaction condition was determined. A transparent modified silica sol with high stability was obtained when the pH value was 10 and the reaction progressed at 20℃for 2 hours and then continued at 70℃for 8 hours, with the molar ratios of reactants as follows, TEOS:KH-560:H2O:IPA=2:5:4:12. The solid content can achieve 37.98% and the gel time can reach two months or more.The modified silica sol was then added into the epoxy resin, the influences of different amounts of modified silica sol on the curing time, curing degree, hardness, adhesive force, water resistance, acid and alkali resistance and surface free energy was investigated. It was found that when the amount of the silica sol reduced, the curing time was significantly decreased from 112 minutes to 50 minutes, while the curing degree decreased at the same time. Moreover, the hardness were significantly increased. The maximum hardness was 0.90 when the molar ratio of epoxy resin and modified silica sol was 4:3. The adhesive force reached lever 3 when the molar ratio was 2:4. The material had excellent water-resistance, which made it not peel from matrixes after immersed in boiling water over 200 hours. The material had high acid-resistance but low alkali resistance. The alkali resistance had improved when the amount of epoxy resin was more than that of modified silica sol, but it worsen rapidly when the more modified silica sol was used. The surface free energy decreased gradually when the amount of the modified silica sol increased.