The 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.
α‐Gel, as a specific lamellar liquid crystal structure, presents unique parameters and attracts broad interest. However, conventional formation of α‐gel involves surfactants that have a long alkyl chain (more than 14 carbons), resulted in limited application into personal care products due to their low Krafft temperature. In this study, a simple way to generate α‐gel was developed using sodium lauroyl sarcosinate, an amino‐acid‐based surfactant containing an alkyl chain with less than 12 carbons. The desired structure was analyzed and discussed. The method, when extended to other amino acid‐based surfactants, gave positive results.
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