The dye which is capable of reacting chemically with a substrate to form a covalent dye-substrate linkage is known as reactive dye.

D-SO2-CH2-CH2-OSO3Na + OH-Cell →D- SO2-CH2-CH2-O-Cell + NaHSO3

Trade name:

1. Poocion
2. Cebacron
3. Remazol
4. Levafix
5. Primazin

Properties:

1. Reactive dyes are cationic dyes.
2. Found in powder or liquid form.
3. Forms covalent bond.
4. Soluble in water.
5. Very good light fastness properties.
6. Very good wash fastness properties.
7. Dyeing method of reactive dye is very easy.
8. Comparatively cheap.
9. Exhaustion & fixation occurs.

Assistant used for reactive dyes:

1. Salt:
   1. Salts are used to increase the affinity of dye to fibre.
   2. Decreases hydrolysis rate of dyes.
   3. Neutralisis electronegativity of fibre surface.
   4. Creates extra energy to push dye inside fibre polymer.
2. Alkali :
   1. Alkali is used to maintain proper pH in dye bath.
   2. It is used as a dye fixing agent.
   3. Strength of alkali depends on the reactivity of dyes.
   4. NaOH→(12.5 – 12) – Strong Alkali
   5. Na2CO3→(11 – 12) – Medium Alkali
   6. NaHCO3→(10 – 11) – Weak Alkali

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