Study On Preparation Of Waterborne Epoxy Emulsion And Characterization

The waterborne epoxy resin can be prepared and used with very little or without volatile organic compounds(VOC), therefore, it is environment-friendly and very attractive in many application fields. In recent years, much more attention has been paid to the preparation and applications of the waterborne epoxy resins.In this paper, for the preparation of water-based epoxy resin emulsion, MAA was used as functional monomer. The emulsion was neutralized by alkali, and dispersed in water to form very stable waterborne epoxy resin dispersion. The reaction temperature, reaction solvent, neutralizer and other processing conditions on the polymerization reaction were discussed respectively.The results showed that when the reaction temperature was about110℃, using environmentally-friendly solvent propylene glycol methyl ether and n-butanol, triethylamine for the neutralizer, the emulsion was stabile with good performance. Infrared spectroscopy and chemical titration were used to proof epoxy groups in system. With increasing amount of MAA, the particle size of modified emulsion was reduced, the conversion rate increased, and the viscosity increased. When MAA reached the maximum amount of25%, the viscosity achieved the peak value, and then decreased. When the amount of initiator BPO increased, the particle size was between200-300nm, monodisperse index was small, and the viscosity decreased. The stability characterization of the emulsion showed that the epoxy emulsion has good stability, especially the storage stability. After storage at room temperature for6months, the solid content of the epoxy emulsion decreased less than1%. When MAA reached the amount of23%, the epoxy emulsion has particle size around the220nm, and narrow particle size distribution. The pure epoxy emulsion paint was synthesized under different conditions, when the temperature was80℃, the amount of curing agent was15%, the overall performance obtained in the film was very good, smooth, no bubbles, adhesion to4, and impact resistance is25kg.cm.In the second step, the water-borne epoxy resin emulsion was modified by silica sol which particle size was about10nm. The effects of different processes and content on the emulsion and film properties have been discussed. The results showed that with the same process conditions, when the silicon content increased, the modified emulsion particle size decreased. Electron micrograph showed that when the silicon content increased, the uneven of the emulsion film surface increased. The increasing of the silicon elemental content in the surface is accord with increasing of water resistance of latex film. At the same time, the heat resistance of the emulsion film increased nearly100℃. The overall performances of the film were better than the pure epoxy emulsion film. With the silicon content increased, the adhesion and impact resistance were increased too.