RESUMEN
Torsional analysis of single human hairs is especially suited to determine the properties of the cuticle and its changes through cosmetic processing. The two primary parameters, which are obtained by free torsional oscillation using the torsional pendulum method, are storage (G') and loss modulus (Gâ³). Based on previous work on G', the current investigation focuses on Gâ³. The results show an increase of Gâ³ with a drop of G' and vice versa, as is expected for a viscoelastic material well below its glass transition. The overall power of Gâ³ to discriminate between samples is quite low. This is attributed to the systematic decrease of the parameter values with increasing fiber diameter, with a pronounced correlation between Gâ³ and G'. Analyzing this effect on the basis of a core/shell model for the cortex/cuticle structure of hair by nonlinear regression leads to estimates for the loss moduli of cortex (Gâ³co) and cuticle (Gâ³cu). Although the values for Gâ³co turn out to be physically not plausible, due to limitations of the applied model, those for Gâ³cu are considered as generally realistic against relevant literature values. Significant differences between the loss moduli of the cuticle for the different samples provide insight into changes of the torsional energy loss due to the cosmetic processes and products, contributing toward a consistent view of torsional energy storage and loss, namely, in the cuticle of hair.
Asunto(s)
Preparaciones para el Cabello/química , Cabello/química , Fenómenos Biomecánicos , Elasticidad , Humanos , Modelos Teóricos , ViscosidadRESUMEN
Through measurements of three different hair samples (virgin and treated) by the torsional pendulum method (22°C, 22% RH) a systematic decrease of the torsional storage modulus G' with increasing fiber diameter, i.e., polar moment of inertia, is observed. G' is therefore not a material constant for hair. This change of G' implies a systematic component of data variance, which significantly contributes to the limitations of the torsional method for cosmetic claim support. Fitting the data on the basis of a core/shell model for cortex and cuticle enables to separate this systematic component of variance and to greatly enhance the discriminative power of the test. The fitting procedure also provides values for the torsional storage moduli of the morphological components, confirming that the cuticle modulus is substantially higher than that of the cortex. The results give consistent insight into the changes imparted to the morphological components by the cosmetic treatments.
Asunto(s)
Cabello/química , Cabello/fisiología , Fenómenos Biomecánicos/fisiología , Cabello/efectos de los fármacos , Preparaciones para el Cabello/farmacología , HumanosRESUMEN
A system to determine the efficacy of hair treatments in terms of anti-breakage and split end prevention was developed which involves the repeated combing of hair strands. The device allows ten hair strands to be combed simultaneously. First, the influences of chemical hair treatments like bleaching on hair breakage were examined. In a next step, the protective effects of benchmark products from the market were studied. Since nearly all commercial products with anti-breakage claims contain silicones combined with cationic polymers, alternative actives were searched. In a test series with different waxes in shampoo formulations with a variable number of parameters, the particle size was found to be the factor with the strongest influence on the amount of wax deposited on the shampooed hair. Therefore, a targeted development was started, resulting in a combination of several ethers dispersed in sodium laureth sulfate. Excellent conditioning, anti-breakage and split ends protection properties of the compound were found, showing also a dosage dependency. The latter could be explained by analyzing the amounts of waxes applied on treated hair. In these experiments, a dependency on the concentration in the shampoo was found.
Asunto(s)
Fenómenos Biomecánicos , Diseño de Equipo , Preparaciones para el Cabello/farmacología , Cabello/química , Cabello/ultraestructura , Preparaciones para el Cabello/química , Preparaciones para el Cabello/normas , Humanos , Resistencia a la Tracción , Agua/química , Ceras/análisisRESUMEN
The determination of silicones and hydrogenated didecenes deposited on human hair from shampoo applications is described. For silicones, induced coupled plasma optical emission spectroscopy (ICP-OES) of extracts and X-ray fluorescence analysis (XRF) of hair strands without any further sample preparation have been applied. Three shampoos from the European and Asian markets have been investigated at repeated shampoo applications followed by the determination of the removability with sodium laureth sulfate. Hydrogenated didecenes have been quantified by GC-MS of extracts. A transparent shampoo containing 1.8% of hydrogenated didecenes delivered via a nanoemulsion was examined in the same way as the commercial shampoos. Finally, the substantivity data were compared with performance data from combability determination and hair volume measurements. Good correlations of analytical data and performance profiles have been obtained.