There are many factors influencing the preparation of waterborne epoxy resin emulsions by the reverse conversion technique, such as the amount of emulsifier, emulsification temperature, emulsification time, and co-solvent dosage. In this paper, epoxy resin E-51 is used to prepare waterborne epoxy emulsion, and the effects of emulsifier dosage and emulsification time on the performance of epoxy emulsion and coating film are discussed.
Epoxy E-51 emulsions with different emulsifier content were prepared by the reverse rotation method at an emulsification temperature of 65°C and an emulsification time of 1.25h. Impact,
As the amount of emulsifier increases, the particle size of the emulsion becomes smaller; when the amount of emulsifier is greater than 10%, the particle size of the epoxy emulsion does not change much. This phenomenon can be explained by the reverse mechanism: as the amount of emulsifier increases, when deionized water is slowly added in the process of preparing the epoxy emulsion, there are enough emulsifier molecules to diffuse to the surface of the newly formed water droplet in time. Coating, thereby forming an interface film with a certain surface tension, can ensure that the water droplets have a constant size, at this time the repulsive force between the water droplets is greater than the attractive force. As the amount of water further increases, the surface tension of the water droplets decreases, and the water droplets dispersed in the epoxy resin change from the dispersed phase W/O type (water-in-oil type) to the continuous phase O/W type (oil-in-water type). On the contrary, the prepared epoxy emulsion has a relatively small particle size.
Effect of emulsifier dosage on emulsion viscosity and dilution stability
Using different emulsifier dosages, the viscosity and dilution stability of the epoxy emulsion were investigated. The results are shown in Figure 2.
As the amount of emulsifier increases, the viscosity of the epoxy emulsion increases and the dilution stability becomes better. The effect of the amount of emulsifier on the viscosity and dilution stability of the emulsion may be related to the critical micelle concentration. When the amount of emulsifier is lower than the critical micelle concentration, the viscosity of the emulsion increases rapidly with the increase of the amount of emulsifier, and the dilution stability of the emulsion also becomes better; when the amount of emulsifier is higher than the critical micelle concentration, the The oxygen emulsion system has been completely reversed, the excess emulsifier molecules cannot re-emulsify the emulsified epoxy resin particles, and the emulsion viscosity and dilution stability have not changed much.