DYES IN CHEMISTRY Submitted To : Submitted By : Dr. Ramesh Thakur (Subject Incharge) Submitted By : Jagmeet Kaur B.Sc (Hons) Biotechnology R280 A 13

INTRODUCTION The process of dyeing involves the immersion of a fabric in a solution of a dyestuff in water. The first dye made was ‘Indigo’ but Blue dyes displaced it because it was faster to light and washing. The most important of the colorants are collectively known as ‘Vat’ dyes. The Fibre – Reactive dyes were designed for cellulose fibres. It has 4 different components – Chromogen, Bridging group, Fibre – Reactive group and Water Solublising group

TYPES OF DYES Natural Dyes – Indigo and madder – used in Japan and Turkey. Synthetic Dyes – In 1856, William Henry Perkin invented these dyes in London from coal tar. The first synthetic dye was Picric Acid.Today these dyes are used in the field of textiles, Medicine, Chemistry, etc. Mordant Dyes - These dyes can be applied only with a mordant and are used for wool. Alizarin is an example. Azo Dyes – These contain an azo group, -N=N- and are used in foods and textiles. These dyes can give a complete rainbow of colors. These dyes are very cheap to produce, are much more stable in whole pH range, are heat stable and not soluble in oils.

Vat Dyes – These dyes are obtained through oxidation, are very bright and hold up better when bleached. These are called ‘Vat Dyes’ because they are originally insoluble in water, they undergo special preparation in large vats before the cloth is introduced. Hair and Food Dyes – Hair dyeing is achieved with a synthetic dye applied with hydrogen peroxide that first bleaches the natural pigment melanin. Dyes and synthetic colorants are used in food. Many food dyes are banned because they cause cancer.Food Additives are added in it. Disperse Dyes – These are used for dyeing of cellulose acetate,polysters,nylon and acrylic fibres. Sulphur Dyes – These dyes are used to dye cotton with dark colors. Sulphur Black 1 is the largest selling dye. Direct Dyes – These dyes are used on cotton, paper, leather,wool,silk and nylon and are used as pH indicators.

Digital Textile Printing The process of directly printing the textile dyes onto the pre treated fabric is called Digital Textile Printing. It is far better than Traditional Printing methods in terms of flexibility, time, purposes, applications and variety of designs. The Dye Inks which are commonly used for this printing are Acid dye inks, Reactive dye inks and Disperse dye inks.

These are Switchable dye molecules for Non – Linear Optics. The chemical known as Aniline consists of a benzene ring substituting on an ammonia molecule. To make the dyes, the manufacturers take aniline and stick it with compounds with alternating double and single bonds. The idea is that these compounds extract the colors from white light to appear red, blue, etc. When these compounds are exposed to intense UV light, it breaks apart the double bonds, causing the color to dissipate. That’s why Aniline dyes get fade. These are Switchable dye molecules for Non – Linear Optics.

REFERNCES THANK YOU www.Yahoo.com www.Wikipedia.com Pradeep’s Chemistry Book of XII class. THANK YOU