SHAMPOO ANALYSIS 319 streaming potential potential traces obtained for this material show both high maximum and equilibrium values as compared to single-charge quartenary ammonium surfactants such as, for example, cetyltrimethylammonium chloride (3). Similarly to other cationic surfactants, Schercoquat DAS reduced the conductivity of the plug to below baseline value within a few rinsing cycles after the treatment. As suggested before, this shows that the fibers do not release appreciable amounts of ad(b)sorbed surfactant into the test solution, and may be indicative of the penetration or rearrangement of the initially adsorbed cationic surfactant molecules inside the bulk of the fiber (3). The flow rate data presented in Figure 2b also suggest a 6% decrease in permeability of quat-treated plug in comparison with hair after exposure to SLES-2, the difference being slightly higher than the limits of the experimental error. In contrast to cationic surfactants, cationic polymers adsorb at the hair surface in a nearly irreversible fashion (6). In the case of Jaguar C17, which is a guar gum modified by the reaction with glycidyltrimethylammonium chloride, the signs of the streaming and zeta potentials are reversed after the treatment and remain constant throughout the whole rinsing cycle. The polymer, which forms turbid dispersions rather than clear solutions in water, significantly reduces the permeability of the plug by evidently forming thick deposits on the fiber surface. Such a behavior is similar to that observed for other cationically modified guar gums, but contrasts with that noted for synthetic, water- soluble cationic polymers, which even at a considerably higher concentration (0.5%) adsorb in the form of thin layers on the fiber surface (3). Figure 3a-d presents the data obtained for amphoteric and nonionic detergents, which are frequently included in commercial cleansing products. The dynamics of the inter- action of hair with such surfactants cannot be unambiguously probed by the use of DEPA because of their uncharged nature. One can only draw conclusions from the relative variation in streaming potential and conductivity. In general, for two ampho- teric surfactants, cocamidopropyl betaine (CAPB) and cocamidopropyl hydroxysultaine (CAPHS), and three nonionic surfactants, Triton X-100, Triton X-405, and Tergitol TMN-6, the changes in electrokinetic parameters and permeability before and after the treatment are relatively small. Both amphoteric surfactants contain salt as a contami- nant, which might be responsible for an increase in plug conductivity observed imme- diately after the treatment cycles. As a result of washing with Triton X-405 and CAPHS, a small decrease in zeta potential is evident, especially after the second treat- ment cycle. Although both surfactants possess no excess charge, and thus cannot modify the surface potential by neutralization, if it plausible that they can screen the intrinsic surface charge by adsorption. This could be responsible for the observed transient reduction in zeta potential immediately after the treatment. It should also be noted that the application of the surfactant solutions results in a significant lowering of the plug conductivity, and in the case of betaine, Triton X-100, and Tergitol TMN6, an increase in the value of the streaming potential. Both phenomena may reflect the removal of loosely bound electrolytic species (including hair lipids) from the fiber by a dilute surfactant solution. NONCONDITIONING SHAMPOOS BASED ON ANIONIC SURFACTANT Figure 4a-c presents the electrokinetic and permeability traces obtained for hair treated with 1% and 10% solutions of shampoo A based on sodium C14-C16 olefin sulphonate,

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