A dye, which is capable of reacting chemically with a substrate to form a covalent dye substrate linkage, is known as reactive dyes.
The reactive dyes constitute the most commonly used class of dyes for dyeing cellulosic textiles, because of their good all-round properties, such as water solubility, ease of application, variety of application methods, availability of different shades, brightness of color shades, good to excellent wash and light fastness and moderate price. Reactive dyes may have poor fastness to chlorine bleach.
Here the dye contains a reactive group and this reactive group makes covalent bond with the fibre polymer and act as an integral part of fibre. This covalent bond is formed between the dye molecules and the terminal –OH (hydroxyl) group of cellulosic fibres on between the dye molecules and the terminal –NH2 (amino) group of polyamide or wool fibres.
Properties Of Reactive Dyes
- Reactive dyes are cationic dyes, which are used for dyeing cellulose, protein and polyamide fibres.
- Reactive dyes are found in power, liquid and print paste form.
- During dyeing the reactive group of this dye forms covalent bond with fibre polymer and becomes an integral parts of the fibre.
- Reactive dyes are soluble in water.
- They have very good light fastness with rating about 6. The dyes have very stable electron arrangement and can protect the degrading effect of ultra-violet ray.
- Textile materials dyed with reactive dyes have very good wash fastness with rating about 4-5 due to strong covalent bonds formed between fibre polymer and reactive group of dye.
- Reactive dye gives brighter shades and has moderate rubbing fastness.
- Dyeing method of reactive dyes is easy. It requires less time and low temperature for dyeing.
- Reactive dyes are comparatively cheap
- Reactive dyes have good perspiration fastness with rating 4-5.
- Reactive dyes have good perspiration fastness.