Project report on effect of Oxidizing Agents on Dyeing Cotton Fabrics with Vat Dye

Abstract

The word vat means, ‘Vessel’. The dyes take their name from vatting. The vat dyes are naturally coloring matter and kept in wooden vat and make solubilize vat dyes by the process of fermentation – so it is called vat dyes. Vat dyes are different from reactive dyes, disperse dyes, basic dyes, acid dyes or azoic color but its application process is near similar as sulphur dyes. Vat dyes are used for coloring cellulosic fiber specially cotton fiber. It is widely used for run the dyeing process of cotton yarns which is used for producing jeans or denim product. Vat dyes provide textile material with the best color fastness of all the dyes in common used for cotton fabric. Most vat dyes are found in insoluble oxidized form. The first operation therefore, it requires a reducing agent to solubilize them. This reducing agent converts the dye to its "leuco" form that is soluble. This process commonly referred to as vatting. Once attached to the fabric, the leuco dye is then oxidized to the insoluble state. Two types of oxidation may be done, physical oxidation which is done with atmospheric oxygen and another is chemical oxidation which is carried out with different types of oxidizing agents. Different oxidizing agent gives different color fastness properties. But, the problem is that if the oxidation is done well, the sample will show a bad colorfastness property. We have done a research and it is entitled as" Effect of Oxidizing Agents on Dyeing Cotton Fabric with Vat Dye”. During research, we have applied two types of oxidation physical as well as chemical on cotton fabric dyed with vat dye. We have used hydrogen peroxide and sodium per borate as chemical oxidizing agent to analyze the effect on colorfastness properties of eight types of 100% cotton fabric sample like single jersey-140 GSM, single jersey-280 GSM, 2×2 rib, single lacoste, fleece, interlock, slub single jersey which are dyed with vat dye. Then we have gone through some tests like colorfastness to rubbing for dry and wet condition and colorfastness to wash. Finally, we have come to a decision that the colorfastness properties of the samples which are oxidized with chemical oxidation is better than that are oxidized with physical oxidation. Again, among the chemically oxidized samples, the colorfastness properties of the samples which are oxidized with sodium perborate are better than that are oxidized with hydrogen peroxide.