Study On Light Fastness Finishing Of Natural Plant Colorant By Natural Antioxidants

Natural dyes are very friendly for environment and human body and its colouration is particular and gentle. Some dyes have function of natural health maintenance. It is tendency to develop and use natural dye and pay more attention to the old theme of using natural dyes, but natural dye also has its limits. Besides some dyes, natural dyes generally have problems of bad dyed fastness, especially light and washing fastness. Eventhough the fastness of most dye is not up to standard by using mordant. Because these, the generalization and application of natural dye are impeded.Light fastness treatment of natural was discussed in this test. In this test, materials and drugs were viridis, and chose berberine and sapanwood as study objects and natural antioxidants L-Ascorbic acid and gallic acid as liaght fastness treatment agents. The natural antioxidants were treated on cotton and silk fabric by the menthod of finishing, pretreatment and one bath dyed process. The light fastness function of antioxidants was studied by changing concentrations. The compatibility between natural antioxidants and dyes were discussed. Because the aqueous solution of L-Ascorbic acid and gallic acid was acor, over-strain experient was carried on the cotton fabric treated by the different concentrations of antioxidants.The results showed that treated by L-Ascorbic acid and gallic acid, discolorous speed of berberine and sapanwood on fabrics were slow down. While increasing the concentration of antioxidants, chromatic aberration of fabric diminished and the light fastness function was better. The improvement of light fastness due to antioxidant action of antioxidants to colorant, and under the administer radiation of light, dyes can formed free radical themself. The antioxidants can scavenge the free radical and preserve the dye without being decomposed or change of constitutional formula. Otherwise, oxygen can also form the free radical by the menthod of overshoot or photochemical reaction and oxyradical had fortis oxidation function. If oxyradical was not scavenged in time, the dye would be decomposed. Absorption curves of mix liquid of natural dye and antioxidants and pure dye were consonance and did not emerge the new absorption peak or peak value excursion, which showed that compatibility of dye and antioxidants was good and it did not affect the natural dyes to using antioxidants as light fastness agent. Compared the colouration and light fastness of cotton with silk fabric treated by different treatments, it showed that the treatment effected on the light fastness of fabric and the effect relation of treatment was sorted. The over-strain experiment of cotton fabric showed that increaing concentration of antioxidants, acor of liquid became stronger. When concentration of L-Ascorbic acid was 25g/L, the over-strain of cotton fabric decrease 9% and pH of liquid was 1. When concentration of gallic acid was 10g/L, the over-strain of cotton fabric decrease 10% and pH of liquid was 2.L-Ascorbic acid and Gallic acid can relieve the color fading of natural dye, but the light fastness was not good enough. However, it is needed to make clear that much more researches are necessary to propose an exact mechanism for this study.