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Popularity of reactive dye The amount of salt and used depends upon the shade
to be produced.
Reactive are mostly used for dyeing cellulosic fibres. At
past cellulosic fibres were dyed with direct and vat dyes, • For light shade – 10gm/ L salt is used.
but after the introduction of reactive dyes there utility has • For medium shade – 20 gm/ L salt is used.
become limited. Reactive dyes are superior to direct dye
in the following aspects: • For dark shade – 30gm/L salt is used.

1 Ability to procedure bright shades of wide range. Alkali
2 High levelling quality. Alkali is used for the following purposes:
3 Good washing fastness. • Alkali is used to maintain proper pH in dye bath and
thus to create alkaline condition.
4 Good light fastness.
• Alkali is used as a dye-fixing agent.
Properties or characteristics of reactive dye
• Without alkali no dyeing take place.
1 Reactive dyes are anionic dyes, which are used for
dyeing cellulose, protein and polyamide fibres. • The strength of alkali used depends on the reactivity
of dyes.
2 Reactive dyes are found in power, liquid and print
paste form. • As strong alkali caustic soda is used to create pH
12.5-12.
3 During dyeing the reactive group of this dye forms
covalent bond with fibre polymer and becomes an • As medium alkali soda ash (Na2CO3) is used to
integral part of the fibre. create pH 11-12 when dye is of medium reactivity.
4 Reactive dyes are soluble in water. • As weak alkali NaHCO3 is used to create pH 10-11
when dye is highly reactive.
5 They have very good light fastness with rating about
Urea
6 The dyes have very stable electron arrangement and
can protect the degrading effect of ultra-violet ray. Urea is used in continuous method of dying. It helps to
get required shade of dye. To get dark shade more urea is
7 Textile materials dyed with reactive dyes have very used and to get light shade less amount of urea is used.
good wash fastness with rating about 4-5 due to strong
covalent bonds formed between fibre polymer and Soaping
reactive group of dye. By soaping, the extra color is removed from fibre surface.
8 Reactive dye gives brighter shades and has moderate Thus washing fastness is improved. Soaping increases
rubbing fastness. the brightness and stability of the dye.
9 Dyeing method of reactive dyes is easy. It requires Factors considered for selection of dyes
less time and low temperature for dyeing. Dye selection depends upon the following factors:

10 Reactive dyes are comparatively cheap 1 Selection of dying method: Dye selection depends
11 Reactive dyes have good perspiration fastness with on dyeing method, which may be:
rating 4-5. a Batch wise/ discontinuous method
12 Reactive dyes have good perspiration fastness. b Semi-continuous method i.e.

Assistants used for dyeing with reactive dyes • Pad – batch method
The following assistants are used in dye bath for dyeing • Pad – jig method
with reactive dyes.
• Pad – roll method
Salt
c Continuous method i.e.
As a salt NaCl is used widely. The salts do the following
things- • Pad – steam method

• Salts are used to increase the affinity of dye to fibre. • Pad – dry method
• It decreases the hydrolysis rate of dyes. • Pad – thermo fix method
• It neutralizes the electro negativity of fibre surface This dyeing method selection depends on:
when immersed in solution. 1 Speed of dye diffusion on the fibre.

• It puts extra energy to push the dye inside the fibre 2 Affinity of dye to fibre
polymer i.e. increase absorption of dye.
3 Reactivity to dye stuff.

Textile & Handloom: Shawl Weaving Artisan : (NSQF - 2024) R.T. Ex.No 1.6.55-65 85