Chemistry Project Report on “Dyeing of Fabrics”
I, ____________ student of ___________________ is doing project report entitled “Dyeing of Fabrics” being submitted to ___________________is an original piece of work done by me.
Dyeing of Fabrics are coloured compounds used for imparting colour to the textiles, silk, wool, food stuffs, etc. A dye is an organic compound which can absorb some band of the light falling on it. The rest of the light is reflected. The reflected light will eventually have colour complementary to that of the absorbed. A dye may absorb all visible light except one band that may be reflected. The dye will then have colour of the reflected band.
Classification of Dyes Based on Application
1. Acid Dyes : Acid media is required for application of this dye. The substantivity of this dye is maximum to wool and least to cellulosic fibre. The acid causes adverse effect on silk in terms of appearance. The dye has good fastness to light. These dyes, which are sodium salts of organic acids just as sulphuric acid, have poor washing fastness property.
2. Basic Dyes : These dyes are the salts of the coloured basic groups containing amino group ( --NH2 or - NR2 ). Modified nylon and polyesters can be dyed with these dyes.
e.g. Aniline Yellow and Malachite Green
3. Direct Dyeing of Fabrics : These are the Dyes which can be applied directly to the fabrics from an aqueous solution. These are most useful for fabrics which can form hydrogen bonds with the Dyeing of Fabrics. Thus they are used for dyeing cotton, wool, silk, rayon, nylon.
e.g. Congo red and Martius yellow
4. Insoluble Dyeing of Fabrics : These are Insoluble Dyeing of Fabrics compounds produced in site on the surface of the fabric i.e. why they are also called as ingrain Dyeing of Fabrics. The reaction involves the coupling between napthal absorbed on the surface of the fabric with the diazonium salt. As there is only surface absorption, the colour is not very fast. These Dyeing of Fabrics are generally used for dyeing cotton, silk, nylon, polyester etc.
e.g. Orange - 1
5. Vat Dyeing of Fabrics : These are insoluble Dyeing of Fabrics which are first reduced to a colourless form in a large vat with a reducing agent such as alkaline sodium hypo-sulphite and then applied to the fabrics.
6. Fibre Reactive Dyeing of Fabrics : These are the Dyeing of Fabrics which contain a reactive group which combines directly with the hydroxyl or the amino group of the fibre. Because of the chemical reaction the colour is fast and has a very long life. Cotton, wool or silk can be dyed with this type of Dyeing of Fabrics.
7. Disperse Dyeing of Fabrics : These Dyes are water soluble Dyeing of Fabrics which are dispersed in suitable reagents before application to the synthetic fibres. These Dyeing of Fabrics Dyeing of Fabrics are used for dyeing nylon and polyester.
8. Mordant Dyeing of Fabrics : These Dyeing of Fabrics do not dye the fabric directly but require a binding agent known as mordant. The mordant acts as a binding agent between the fibre and the dye. These are used to dye wool.
e.g. Alizarin (Turkey Red).