Black Pearls Dyed By Quinone Imines And Research On Resist Against The Effect Of Environment

Pearls are used as decoration, drugs and cosmetic, and it's quit popular in China too. Pearls have five kinds of colors, such like white, yellow, red, dark and mottle. The person of the different nation, different race may have their distinct favor of different color of pearl. But no matter crude pearls or cultured pearls, the color, the luster or the saturation of the pearls are below satisfied. So people invent many methods to prepare the dyed pearls. In the mean time the color of the dyed pearls is not stable under the exposure of the sunshine, and pearls are damaged by the sweat, grease and alcohol. It's quit important to research on the mechanism of the color fading and fide some new method to dye the pearls.In this work, the preparation of black chemical colored freshwater cultured pearl dyed by Quinone imines and the mechanism of color fading of pearl dyed by azo dyes are investigated; the preparation of golden pearls dyed by mixed dye was discussed; nanosized TiO₂ particle-polymer co-modified method was applied to the golden pearl to protect it from the ultraviolet radiation and the sweat successfully. The color fading behavior is researched comparing the color fading phenomena of the azo dyed pearls under the UV and sweat. The investigation on the infection of nanosized TiO₂ particle-polymer co-modified prepare condition to the performance is discussed.In the first part of the paper, freshwater cultured pearl was colored by quinone imines intermediate. The reflectivity and the luster of the pearls are measured by visible spectrophotometer and Raman spectroscopic analysis. Then the color fading of dyed pearls under the UV was discussed. The results indicated that pearls dyed by quinone imines are stable under the UV. This result gives a feasible way to prepare anti-color fading pearls. The technology of mixed dye is tested, and the golden pearls are produced. The stability of the golden color is tested.Secondly, the color fading behavior is researched considering the color fading phenomena of the azo dyed pearls under the UV and sweat. The results indicated that the maximum absorption wavelength of azo dye used to dye the pearls changes because of the structure changing from azo to quinone imines and the degradationreaction which causes the color fading. The dye molecule attaches to the protein fiber of the pearls, and the electron group slow down the color fading. The speed of color fading is different according to the structure. The acidity of sweat damages the pearls itself and the dye inside the pearls. The sweat erodes the horn face and the organic matter, and filter into the pearls to solve the dye. This behavior causes the color fading and luster falling. The speed of damage to the pearls is different according to the alkalescence of dyes.Finally the nanosized TiO₂ particle-polymer co-modified technology is applied to the cultured pearls, and the investigation on the infection of nanosized TiO₂ particle-polymer co-modified prepare condition to the performance is discussed. The quality of the co-modified pearls from different prepare conditions are analyzed by visible reflectance spectra. The results indicated that the co-modified pearls are light yellow, which is the color of nanosized TiO₂ film. With the irradiation of UV, the nanosized TiO₂ film turns to blue, the opposite color of yellow. According to the tricolor theory, if yellow and blue mix together, it's white. At the same time co-modified pearls are as bright as the cultured pearls. The polymer film is tend to be smooth with the effect of the sweat. Compared with the diathesis of the pearls the prepare condition is not a influencing factor to the performance of the co-modified pearls.