Bleaching
After
the removal of the waxes and other hydrophobic type of
impurities from gray fabric by the desizing and scouring the fabric is now in a
more absorbent state. But still have the pale appearance due to the presence of
natural colouring materials like pigments etc. these pigments can not be removed
the only way to tackle these pigments is to decolourise them using suitable
oxidising agents. This will make the fabric in a super white form. This process
of decolouration of natural pigments is called the bleaching. The process of
bleaching gives a sparkling whiteness to the fabric and hence makes it suitable
for further processing.
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| Bleching |
Methods of
Bleaching
The various chemicals employed to carry out
bleaching process are:
1.
Dilute
hypochlorite solution preferably Sodium Hypochlorite (NaOCl)
2.
Hydrogen
Peroxide (H2O2) solution
3.
Sodium
Chlorite (NaClO3) solution
4.
Certain
peroxy compounds like peracetic acid
5.
Potassium
Permanganate (KMnO4) solution
Now we
discuss the effect of different bleaching agents under various conditions of
concentration, pH, temperature, time and activators. So that we can choose
optimum conditions of bleaching with a particular bleaching agent.
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