Diethanolamine Esterquats for Hair and Skin and Other Topics: Literature Findings

By: Charles Fox, Independent Consultant

Posted: May 4, 2009, from the May 2009 issue of Cosmetics & Toiletries.

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mixturesa. Stress measurements of the individual components of the biopolymer mixture and their combinations showed a higher zero shear viscosity for the mixture than its individual components. This indicated a synergetic effect in the KX blend, which is attributed to the interaction between the two polysaccharide molecules.

Rheological measurements for the surfactant-biopolymer mixtures showed a reduction in the zero shear viscosity when compared with KX alone, indicating that the surfactants reduced the interaction between the two polysaccharides. Rheological investigations were conducted using the mixtures at various intervals of time, and the results showed high stability of the emulsions both at RT and higher temperatures. The emulsions also showed no separation or creaming as a result of the presence of a gel network in the continuous phase. However, the emulsions are shear-thinning and their viscosity reached low values at high shear rates.

Several emulsions were prepared and their sensory attributes were determined using expert panels. The results obtained were assessed using statistical analysis. The sensory attributes of several emulsions based on these surfactant/biopolymer mixtures were compared with those obtained using classical surfactants and hydrocolloids such as carbomer. Generally, the emulsions based on the emulsifier/biopolymer mixtures showed higher spreadability, higher wetness, lower firmness, lower greasiness, lower thickness and lower integrity of shape compared with the other emulsions. This was mainly due to the lower viscosity at high shear rate and the lower (but coherent) gel structure, which can be easily broken under shear. With the emulsions containing thickeners such as carbomer, a higher cohesive energy was obtained and the gel structure could not be easily broken under shear. These results indicate that, in personal care emulsions, surfactant/biopolymer mixtures provide formulating advantages.

O/W moisturizing emulsions: Carlotti et al. have published on o/w moisturizing emulsions with two saccharose esters, saccharose palmitate and saccharose stearate.¹⁴ The ability of saccharose esters to form lamellar structure in oil/water/glyceryl stearate mixtures was investigated through ternary phase diagrams. Three different oils were tested including mineral oil, C12-15 alkyl benzoate and cetearyl octanoate.

On the basis of the phase behaviors, several emulsions with liquid crystal structures were obtained and then characterized. Furthermore, the most stable emulsions were combined with one of two moisturizing actives, lauryl pyrrolidone or sodium-d,l-pyroglutamate. After the addition, the stability of the emulsions was assessed. It was observed that emulsions containing sodium-d,l-pyroglutamate were less stable compared to emulsions containing lauryl pyrrolidone.