EFFECT OF BLEACHING AGENTS ON NATURALLY COLOURED COTTON YARNS
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Date
1999-09-09
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
The present study entitled effect of bleaching agents
on naturally coloured cotton yarns was carried out during
1997-98 at Dharwad with the objective to study the effect of
scouring, bleaching, mercerisation on naturally coloured cotton
yarns. Three brown coloured namely Dharwad light brown
hirsutuni (DLBH-95-1), Dharwad medium brown hirsutum (DMBH-
95-1), Dharwad dark brown hirsutum (DDBH-95-1) and one
Dharwad green hirsutum (DGH-95-1) were selected for the
study. The experiment was carried out at yarn stage included
treating the yarns with scouring agents namely soda ash (Sj),
a mild alkali and a mixture of soda ash and caustic soda (S2), u
strong alkali. Bleaching was carried out for Sj and S2 scoured
genotypes with calcium hypochlorite, hydrogen peroxide, sodium
hydrosulphite and sunlight separately. On scouring, bleaching
and mercerisation the single yarn strength and colour change
was assessed using computer colour matching system under
daylight, tungsten, tubelight-83 and tubelight-84 illuminations.
Scouring increased the single yarn strength and colour of all
the genotypes. However, higher improvement in the single
yarn strength was evident on 83 scouring where as maximumimprovement on colour was on Sj scouring when assessed
under all the light illuminations. Sunlight bleaching increased
the single yarn strength of all the brown genotypes and
reduced the strength of green genotype. Bleaching resulted in
the fading of colour of all the genotypes however, they
appeared darker than the control. All the selected naturally
coloured cotton genotypes bleached unevenly with calcium
hypochlorite and further it reduced hue intensity of coloured
cottons. There was minimal fading of the colour on sodium
hydrosulphite bleaching and was moderate with hydrogen
peroxide and sunlight bleaching. Mercerisation did increase
the single yarn strength and colour of all the selected
naturally coloured cotton genotypes.
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