Mechanism And Characterization Of Dye-free Coloration For Protein Fiber By Adding Tryptophan

Clothing, as an integral part of people’s daily necessities, has been widespread concerned. With the improvement of people’s living standards and the promote of green chemistry, green, eco-friendly textiles received more and more people’s attention. Dye free technologies, one of eco-dyeing, came into being with the philosophy of green and low-carbon.Dye-free makes the use of the combination of tryptophan in protein fiber and benzaldehydes, increasing the length of conjugated double bonds in substance, resulting that material has a specific absorption in the visible region, so that the protein fabric exhibits a certain color. However, content of tryptophan in protein fabric is limited, affecting the color yield and depth. The additional tryptophan was used to improve the content and purity of Trp in fabric, in order to improve the depth and saturation of dye- free colored fabric. The experimental results demonstrated the feasibility of this method.The E of colored tussah used two-step method of tryptophan added got a increase of 4.43 compared to the tussah dyed-free directly. Tryptophan, which had uniform properties, added more uniform distributed in surface of fabric than those native. Thus, the uniform of the color of dyed- free fabric had been improved(standard deviation changed from 0.185 to 0.165). Color fastnesses of the fabric were excellent, which all were up to 4-5 or above.Detailed experiment concert on conditions for the oxidation was carried o ut, which have a significant impact on the chromogenic method with one-bath. The results showed that hydrogen peroxide was more suitable as the oxidant to dye-free. What’s more, a deeper uniform green can be got by adding 10%(o.w.f.) of hydrogen peroxide at 90℃ for 10 min when using 15g/L of tryptophan and 5%(o.w.f.) of dimethylaminobenzaldehyde in dye-free for tussah silk.Dye free techniques cannot be used in dyeing for protein fabric, but also printing of the protein. Hydroxyethyl cellulose, a strong acid resistance thickener, was used in formulating printing paste, which was consist by tryptophan mass fraction of 7.5%, PHBA of 8%, HC l of 15%, HEC of 2.5%, and H2O2 of 2%. The tussah silk fabric squeegee performed twice and then dried at 80℃ for 30 min showed best printing result. Its printing pattern and outline were clear, and it had deep and uniform color. Meanwhile, the breaking strength of the fabric, color fastness and breathability, softness performs were well. What’s more, a short process was used, which it’s more environment-friendly and more economical.As can be seen from colored fabric treated by different processes and chromogenic reagent, the color of fabric treated by nitric acid had much larger E than hydrochloric acid and sulfuric acid, which basically presented golden yellow; The color of fabric in one-bath was much higher than the fabric in any other craft, showing more brown, but the brightness of the fabric(L*) decreased the most.Added tryptophan method of dye- free technology used in tussah fabric showed that this method can be applied in coloring protein fabric. Dye free fabrics showed exhibit excellent performance, meeting the requirements of environmental protection and needs of people’s living for low-carbon eco-textiles, which is the future trend of dyeing and finishing, and which has a vast market prospects.