Study of hair surface energy and conditioning

Synopsis A new test method has been developed to determine surface energy of hair fi bers through measurements of contact angles at two hair/liquid interfaces. By measuring changes in surface energy of the same hair fi ber before and after a cosmetic treatment, effects of active ingredients and the performance of tested formulations can be evaluated. The establishment of the method is based on Fowkes theory (1,2) described with two components, a dispersive and a non-dispersive component. The non-polar liquid used in this study was diiodomethane, and the polar liquid was benzyl alcohol. A Kruss 100 Tensiometer was used to measure contact angles of hair fi bers. Virgin dark brown and regular bleached hairs were treated with selected conditioner formulations. Reductions in combing forces of hair tresses before and after respective treatments were correlated with decreases in average surface energy of hair fi bers obtained from the corresponding tresses. Experimental results indicate that the average surface energy of hair fi bers treated with conditioners decreases and the hydrophobicity of the hair surface increases, the results correlate well with the reduction in combing forces after respective treatments. This research work provides a new methodology to evaluate/screen conditioning performance of hair care ingredients and formulations for development of better products.