Experimental study of the rheological properties and stability of highly-concentrated oil-based emulsions

This study presents a systematic investigation of viscosity and rheological properties of several dozen emulsions and nanoemulsions. The concentration by volume of the oil in emulsions varied from 20% to 80%. Low-viscosity mineral oils were used for emulsion formation and an aqueous solution of calcium chloride was used as the second medium. The volumetric concentration of emulsifiers varied from 1.5% to 4.5%. Three types of mineral oil, as well as various emulsifiers, are considered. The effect of the volumetric content and base oil type, the emulsifier type and concentration and the ultrasonic treatment duration on colloidal stability, rheological properties and droplet size of the resulting emulsion has been studied. It is shown that emulsions are considered to be non-Newtonian fluids with apparent elastic properties at oil concentration less than 35 vol%. All other things being equal, the average droplet size in the emulsion increases with an increase in the base oil viscosity. The use of ultrasonic treatment makes it possible to reduce the average droplet size in the emulsion by 4.5 times and to reduce its viscosity by 1.5 times.