Development of an evaluation method of the frictional property of human hair - Microscopic mechanism of lowering effect of “squeaky” sensation by shampoo

In the previous study, we proposed a method to evaluate the tactile sensation of human hair during hair washing. By using this method, a sensory score of “squeaky” sensation during hair washing with shampoo was reproduced by the physical indexes obtained by the integration of the reactive force and the frequency analysis of temporal fluctuation. By clarifying the microscopic mechanism of decrease in “squeaky” sensation by using shampoo products, it becomes possible to formulate better hair-care products. In this study, the microscopic interaction between human hair and shampoo components was investigated by using sound analysis and hair surface analysis. It was shown that the “squeaky” sensation can be evaluated by the sound parameters. Furthermore, based on the microscopic observation and identification, the model of microscopic interaction by hydrophilic interaction between hair surface and coacervate was suggested.