Effect of Polyhydric Alcohols, Surfactants, Emollients and Emulsifiers on Phase Behaviors of Ternary Fatty Acid Soap Solutions

Abstract

AbstractThe effects of polyhydric alcohols (glycerol, propylene glycol), surfactants (SLES, CAPB, APG), emollients (stearic acid, IPM, Cetiol CC, Cetiol HE) and emulsifiers (Simusol 165, S1170) on the phase behavior of fatty acid soaps prepared with lauric acid, myristic acid and stearic acid mixtures (25% total fatty acids) were studied. Phase behaviors were analyzed by pH, viscosity, turbidity, clarity, polarization optical microscopy and X‐ray diffraction. The results show that the composition of ternary fatty acid mixtures plays a decisive role in the phase behavior of soap solutions. An increase in the level of steric acid promotes the formation of the Liq + Crystal phase. Polyhydric alcohols made the liquid‐phase (liquid micelle phase) region larger. Surfactants also increased the liquid‐phase region by solubilizing insoluble fatty acid soaps. Liquid‐phase soap systems were stable for at least 2 months. Emollients were solubilized by fatty acid soap micelles leading to the formation of the Cub + Hex and Liq + Lam phases. Emulsifiers showed excellent solubilizing properties in the system of fatty acid soaps and emollients. The liquid‐phase region became larger, reducing the Cub + Hex phase region and keeping the Liq + Crystal phase more compact and stable. The Cub + Hex phase and Liq + Lam phase were metastable with the system eventually separating into multiple phases over time.