What is Dyeing?
The process of applying color to fiber stock , yarn or fabric is called dyeing .
There may or may not be thorough penetration of the colorant into the fibers or yarns . Dyeing is the application of color on fiber in such a manner that color is uniformly applied and material should possess some resistance to the removal of dyes by water .
The fibers should be dyed uniformly throughout their thickness . This is the ideal stage. In practice , dyeing operation is sometime stopped before distribution of dye within fiber as reached uniformity.
What is Dye?
Dyes are complex and organic compounds having substituent group i.e. Chromophore and Oxochrome.
What is Chromophore?
Presence of these groups gives rise to absorption in visible region or u.v.region .
-C = C- Ethylene
-N = N- Azo
-N = 0- Nitroso
-NO2 Nitro
-C = 0 Carbonyl
What is Oxochrome?
Provides Substantivity to substrate . They are acidic or basic functional group .
Such as -
-SO3H Sulphuric acid
-OH Phenolic group
-COOH Carboxylic group
-NH2 Tertiary amino group
-NR4+ Quaternary ammonium
Essential properties of dyes:-
1. Dye should be intense in color .
2. Dye should be soluble in water either permanently at the time of application .
3. Dye should be capable of being absorbed and retained be the fiber or chemically combined with it ( as in reactive ) .
4. They have adequate fastness properties e.g. Capable to withstand action of light , washing and many other agencies normally acting on dyes material .
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