Controlling the emulsion stability of cosmetics through shear mixing process

초록

The manipulation of emulsion stability for kinetically sustainable cosmetic emulsions is an important technology in cosmetic industry, however the relationship between emulsifying process and long-term emulsion stability has not been elucidated. Herein, the effect of shear mixing process on the stability of oil-in-water cosmetic emulsions is investigated by varying the shear mixing rate, emulsification time, and water phase temperature. The analysis on droplet size distribution and shear viscosity revealed that the strong viscous forces at optimal shear mixing rate of 4000 rpm afforded the fine and uniform droplets for cosmetic emulsions, leading to the improvement of long-term emulsion stability. Moreover, since the prolonged shear mixing induced the destabilization of emulsion droplets through droplet coalescence, optimal shear mixing time of 3 min could improve the kinetic stability of cosmetic emulsions. The dependence of long-term emulsion stability on emulsification temperature was relatively low. The theoretical analysis using the Derjaguin-Landau-Verwey-Overbeek theory demonstrated that the shear mixing rate played a major role in sustaining fine and uniform cosmetic emulsions with long-term stability. The present study can greatly contribute to the fabrication of functional cosmetic emulsions with long-term stability by controlling the shear mixing parameters in simple emulsification process.

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