Spray Characteristics of Mist Aerosol Containing Emulsifier-free Oil-in-water Emulsions as Mist Aerosol Formulation

We examine the spray characteristics of mist aerosol containing emulsifier-free oil-in-water (EF-O/W) emulsion, which are prepared by ultrasonic emulsification of only oil and water in the absence of any emulsifiers such as surfactants, as a mist aerosol formulation. We found the unique spray characteristics of mist aerosol containing EF-O/W emulsion, which is a larger angle of mist sprayed and the resulting larger mist area, compared to the water and ethanol as a mist aerosol formulation. The unique spray characteristics observed for mist aerosol containing EF-O/W emulsion were not related to the physical properties of mist aerosol formulations, concentration of oil in EF-O/W emulsions, size of oil droplets in EF-O/W emulsions, size of droplets in mist sprayed from mist aerosol and flow rate of mist aerosol formulation in the actuator. By monitoring the liquid film sprayed from the actuator of mist aerosol, the splitting of liquid film sprayed from mist aerosol containing EF-O/W emulsion occurs at shorter distance from the actuator compared to the splitting of liquid film sprayed from mist aerosol containing water and ethanol. Namely, the earlier splitting of liquid film sprayed from mist aerosol results in the mist with larger angle and larger area of mist sprayed while the later splitting of liquid film sprayed from mist aerosol leads to the mist with smaller angle and smaller area of mist sprayed.