Introduction:
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.
Why reactive dye is so called?
Reactive dyes are so called because this is the only type of dye, which has reactive group, and that reactive group reacts chemically with fibre polymer molecules and form covalent bond. This covalent bond is formed between the reactive group and terminal-OH (Hydroxyl) group of cellulosic fibre and wool fiber or between reactive group and terminal -NH2 (Amino) group of polyamide polymer. The strength of this covalent bond is more than ionic bond, hydrogen bond and Vander Waal’s force of attraction. Thus the reactive group becomes an integral part of the fibre.
Fibres dyed:
By reactive dyes the following fibres can be dyed successfully:
1.Cotton, rayon, flax and other cellulosic fibres.
2.Polyamide and wool fibres.
3.Silk and acetate fibres.
It covers a wide range of color spectrum and includes shades varying from bright to heavy dark like,Violet、Blue、Green、Red、Black、Yellow CTC.
Popularity of reactive dye:
Reactive are mostly used for dyeing cellulosic fibres. At past cellulosic fibres were dyed with direct and vat dyes, but after the introduction of reactive dyes there utility has become limited. Reactive dyes are superior to direct dye in the following aspects:
1.Ability to procedure bright shades of wide range.
2.High leveling quality.
3.Good washing fastness.
4.Good light fastness.
And it is superior to vat dyes in the following aspects:
1.Simple dyeing method therefore one stage dyeing.
2.Low temperature dyeing (below 100℃).
3.Lower cost, i.e. cheaper.
Source：Textile Learner
