Electrical Properties and Characterization of Chitosan Applied in Cosmetics

In this study, we extracted chitosan from shrimp shells by chemical processes of three steps, i.e., demineralization, deproteinization, and deacetylation. Chitosan was applied to improve quality of cosmetic products as a bio-adhesive to enhance electrical properties. By X-ray diffraction (XRD) measurements, crystallography of shrimp shells, chitosan and cosmetic samples were analyzed. theta/2 theta-scan XRD measurements show two distinguishable 2 theta-position peaks of d-spacing of 9.99 (A) over circle and 4.56 (A) over circle of shrimp shells and 9.59 (A) over circle and 4.63 (A) over circle of chitosan with different intensity ratios of the two 2 theta-peaks. For lipstick samples, XRD measurements show different crystal structures of titanium dioxide (TiO2) as rutile and anatase forms. From XRD measurements of all facial-powder samples, there was no significant difference in main crystalline materials of facial powders such as talcum and TiO2. By X-ray fluorescence (XRF) technique, elemental analyses of shrimp shells and chitosan were performed for Ca, P, Cl, Na, S, Mg, K, and Si. In the case of chitosan, the reductions of elemental compositions were observed. In addition, the elemental analyses of lipstick samples were investigated for Ti, S, Si, Al, P, Fe etc. To investigate electrical properties, the capacitances of pure chitosan, pure lipstick samples and chitosan-mixed lipstick samples were measured by a parallel-plate capacitor. Interpreted results from theoretical calculations indicate their dielectric constants (epsilon(r)) of 8.55 +/- 1.95, 3.84 +/- 0.99 and 7.28 +/- 1.26, respectively. For current-voltage (I-V) characteristics using 4-probe measurements, all facial-powder samples were compressed into 1-cm-disc forms by using potassium bromide (KBr) as a neutral-electrical binder. The power voltages were applied to the sample discs but the current signals flowing through the discs were too low to measure by this measurement. However, the voltage across the sample discs allowed electrical measurements. With a variation of applied voltages from 1 V to 18 V, the voltages across pure KBr discs were not detectable. In the case of chitosan discs, the voltages of the discs were measured as an average of 1.483 +/- 0.101 mV at the optimized applied voltage of 15 V. At the applied voltage of 15 V, the voltages across the facial-powder discs were measured as an average of 0.138 +/- 0.013 mV. For chitosan-mixed powder samples with a composition of chitosan of 50%, the voltages were measured as an average of 0.250 +/- 0.032 mV and an average of 0.325 +/- 0.031 mV for a chitosan composition of 70%. These results indicate to ionic/ conductive characteristics of chitosan structures to enhance the electrical properties of facial powders. In summary, the significant changes in capacitances, dielectric constants and electrical conductivities of cosmetic samples by addition of chitosan imply improved electrical properties resulting from a stronger adhesive force by more electric dipoles and stronger electrostatic effects.