Modification Of Waterborne Epoxy Resin Emulsion By Silica Sol

Epoxy resin has excellent mechanical properties,strong bonding properties,and is widely used in coatings,adhesives,engineering plastics and other fields.Epoxy resin is insoluble in water and can only be dissolved in organic solvents such as ketones and aromatic hydrocarbons.Organic solvents are not only flammable,explosive,toxic,but also volatile,which pollutes the environment.Nowadays,the society has paid more attention to the environmental protection problem,and the pollution of the solvent epoxy resin to the environment has aroused the attention of the people,the development of environmental-friendly waterborne epoxy resin has become a trend.After curing,the coating of waterborne epoxy resin has the disadvantages of brittleness,poor flexibility and poor impact resistance,which limits the application of waterborne epoxy resin.The modification of waterborne epoxy resin by silica sol was studied in this paper.The mechanical properties,water resistance and corrosion resistance of waterborne epoxy resin were improved to some extent.First,silica sol was prepared by silicon powder method,the effects of reaction time,reaction temperature and amount of catalyst on the average particle size of silica sol were investigated.The optimum technological condition was determined.In the presence of 0.8 g sodium hydroxide catalyst,20 g silica powder was used to react with 200mL distilled water at 900C for 5 h,the average particle size of the prepared silica sol was 18 nm,the content of silica was 15%.Then the silica sol was modified and the effect of KH560 dosage on the oil-lipophilic effect of silica sol was investigated.The results showed that the modification effect is the best when KH560 content was 7%.Secondly,grafting reaction method were used to modify epoxy resin,the effects of polymerization time,polymerization temperature,BPO content,methacrylic acid content,and neutralization degree on the acid value of the system or the stability of the emulsion were examined to determine the optimum conditions for the preparation of the aqueous emulsion.The silica sol was added into waterborne epoxy resin to prepare compound emulsions.The effect of nano-SiO2 content on emulsion stability and coating properties were studied.With the increase of nano-SiO2 content,the stability of emulsion,the mechanical properties,water resistance,acid and alkali resistance and corrosion resistance of the coating were increased first and then decreased.When the content of nano-silica was 6%,the modified waterborne epoxy emulsion has good stability,excellent mechanical properties,water resistance and corrosion resistance.