Stability estimation of emulsions of isopropyl myristate in mixtures of water and glycerol.

Phase studies were carried out on systems consisting of isopropyl myristate, polysorbate 80, glycerol, and water. The stable oil-in-water emulsion regions were identified. An influence of the glycerol-to-water ratio on the area of existence of stable emulsions was obtained. The Coulter counter technique was used to determine the droplet size in oil-in-water emulsions. A decrease in average particle size with an increase in glycerol and polysorbate concentration was observed 24 hours after the preparation. Rheologically, the emulsions displayed Newtonian behavior. Their viscosities increased with increasing glycerol and polysorbate concentrations. The influence of glycerol and polysorbate concentrations on the cream separation of one-month-old emulsions indicated an increase in emulsion stability with the increase in glycerol and polysorbate concentrations. The use of a polysorbate 80 concentration of 5% by weight can be proposed for stable oil-in-water emulsions of isopropyl myristate in glycerol-and-water mixtures.