Shampoos are cosmetic products which, in addition to their basic function of removing dirt and sebum from the hair and scalp, also provide conditioning properties. For practical use, they must exhibit suitable rheological properties. Thickeners play an important role in achieving these properties, as they affect the viscosity and stability of formulations. As part of our thesis, we studied the effect of different thickeners on the rheological properties of shampoos with proteins.
In the initial phase of development, we reviewed the thickeners most commonly used in shampoos and selected the most suitable ones, which we included in further practical work. The key criteria for selecting thickeners were their water solubility and cationic nature, so that they could form complexes with anionic surfactants. We used hydroxypropyl methylcellulose polyvinylpyrrolidone, polyethylene glycol glyceryl cocoate, hydroxyethyl cellulose, and laureth-2, which we added in various concentrations to the basic shampoo formulation and then optimally incorporated them into shampoos with added whey and hydrolyzed wheat and silk proteins.
We then determined the organoleptic properties, pH, and rheological properties (rotation, amplitude, frequency) of the shampoo formulations. Rheological measurements performed with a rotational rheometer showed that all formulations exhibited non-Newtonian, pseudoplastic behavior. The viscosity was significantly influenced by the type of thickener, its concentration, and the incorporated proteins. The highest viscosities were exhibited by formulations where we used hydroxypropyl methylcellulose K100M as a thickener, while proteins mostly reduced the viscosity of the formulations.
Based on the conclusion, the study provides guidelines for optimizing shampoo formulations, particularly in the selection of an appropriate thickener and its concentration, and emphasizes the need for further research that would also include an assessment of microbiological stability and long-term stability tests.
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