Different kinds of silicone oil emulsions, such as O/W, W/O, O/W/O, were prepared by homogenization, ultrasonic and mechanical stirring methods. However, due to their high inertia, they have poor compatibility with many emulsifiers or surfactants, making it difficult to prepare stable emulsions.
Factors affecting the stability of silicone oil emulsion
Silicone oil viscosity
The size of oil droplet increases with the increase of viscosity, indicating that the silicon oil with higher viscosity is not easy to decompose into small size oil droplet. Therefore, silicone oil with higher viscosity will form emulsion with larger particle size and wider particle size distribution, which further leads to poor stability of emulsion.
Emulsifier concentration
With the increase of the concentration of emulsifier, the particle size of the emulsion decreases, the uniformity of the emulsion improves, and the stability of the emulsion further improves.
Emulsification time
When the emulsifying time is too short, the oil phase cannot be well dispersed, resulting in a wide particle size distribution.
With the prolonging of mixing time, the droplet size decreases, the volume fraction of emulsion increases, and the viscosity increases. The appropriate increase of emulsion viscosity leads to the decrease of droplet motion, which is beneficial to the stability of the emulsion. On the other hand, when the emulsification time is too long, the viscosity of the emulsion increases, leading to the increase of the droplet volume fraction. The overcrowded environment leads to droplet condensation and poor stability. Therefore, emulsification time should be optimized according to different systems in order to improve the stability of emulsion.