Chemical modifications on human hair studied by means of contact angle determination

Wetting properties of a solid surface can change as a consequence of chemic al treatment. There is a relationship between the molecular structure of a surface and the macroscopic properties of this surface such as wetting and adhesion. Information on the surface energy of a solid was obtained by calc ulating polar and dispersion force contributions by means of contact angle determination. The superficial modification undergone by human hair treatme nts with or without hydrogen peroxide at alkaline pH was studied by means o f wetting force measurements. The wetting increase in treated human hair fi bers was analyzed following the Huttinger method using contact angle data, taking into account the acid-base and dispersion components of the total we tting adhesion work. The hydrogen peroxide treatment at alkaline pH leads t o a partial removal of hydrocarbon chains and to the formation of ionic gro ups (cysteic acid residues) on the outer scale cell surface. The latter phe nomenon was observed by means of an increase in the acid-base adhesion work versus water wetting liquid at alkaline pH. (C) 2001 Academic Press.