]. Cosmet. Sci.! 59, 105-115 (March/April 2008) Influence of cellulose polymers on the semipermanent dyestuff process for yak hair: An analytical investigation B. BALLARIN, S. GALLI, and M. MORIGI, Department of Physical and Inorganic Chemistry! Universita di Bologna! V. le Risorgimento, 4 40136 Bologna (B.B.), and Ilios snc, v. L. Basso 170, 47023 Cesena (S.G., M.M.), Italy. Accepted for publication November 28, 2007. Synopsis The aim of this study was to investigate the effect of some cellulose polymers mixed in a semipermanent dyestuff on the dye uptake of yak hair fiber and color fading after repeated washing cycles. Two different classes of commercial polymers were tested: non-ionic and cationic. Formulations based on a mixture of HC and basic dyes, with different molecular sizes, were employed as representative dyestuffs. UV-Vis spectros- copy and colorimetric measurements were used to analyze the extracted dyes from the yak hair cuticle and cortex. The results obtained indicate that the presence of cationic polymers in the dye bath improves both the quality of the dyeing process and the anti-fading effect during the first washing cycles. INTRODUCTION In the past few decades, polymers have become increasingly important components of cosmetics as primary ingredients or additives in shampoos, conditioning and styling products, and hairspray. Generally, they have been used in hair cosmetics as conditioning agents to improve combing, manageability, and body or as components to increase emulsion stability (1). As the main function of the polymers is to be adsorbed reversibly onto the hair surface (2), three types of bond can occur within the hair: primary valence bonds (ionic and covalent bond), polar interactions (primarily hydrogen bonds), and dispersion forces (Van der Waals attractions) (1). Although the interaction of polymers on keratinous surfaces has been described in detail in the literature (1,3-5), very few data are available regarding their influence on the mechanism involving molecule adsorption and desorption on the hair fibers, as, for example, in the hair dyestuff process (6,7). The latter essentially consists of two steps (8): the transport of dye from a dyebath into the fiber and then the subsequent uniform distribution of dye molecules over the available dye-binding sites. Moreover, the transport itself is assumed to be divided into three steps with regard to the transfer of the dye from the bulk of the solution to the fiber surface, Address all correspondence to B. Ballarin. 105

106 JOURNAL OF COSMETIC SCIENCE the sorption of the dye on the surface, and finally the penetration of the dye into the surface (9). Dependent upon the operative conditions chosen, one or another of these steps can assume a prevalent role in determining the outcome of the dyeing process and the quality of the final product. Different parameters can be used for controlling the dyeing conditions (pH, temperature, solvent, etc), the relative contribution of each step can be enhanced or diminished, and thus the course of the overall process can be regulated. In this paper we investigate the effect of two different kinds of cellulose polymers (i.e., cationic and non-ionic), directly incorporated into semipermanent hair dyestuff, on the hair dyeing process. The dyes chosen were a mixture of HC (character- ized by a low size) and basic dyes, the relevant formulas of which are reported in Table I (10-12). The cellulose polymers studied are two quaternary nitrogen-containing cellulose ether polymers: Polyquaternium 10 (30M) and Polyquaternium 67 (SL-60), which differ in the number of cationic charges (one or two positive charges for glucose units, respec- tively) and the degree of hydrophobic substitution (i.e., the presence of dimethyldodecyl ammonium groups). These polymers give predominantly ionic interactions with hair (2) and can be strongly adsorbed and/or diffused into the hair dependently via their ionic HC Yellow 2 HC Blue2 Basic Red 51 Table I Dye Formulas