Experiment Name: Dyeing of 100% cotton knitted fabric with direct dye.
Theory: Direct Dye is a class of dyestuff that are applied directly to the substrate in a neutral or alkaline bath. They produce full shades on cotton and linen without mordanting and can also be applied to rayon, silk, and wool. Direct dyes give bright shades but exhibit poor wash fastness. Various after treatments are used to improve the wash fastness of direct dyes. Direct Dyes are molecules that adhere to the fabric molecules without help from other chemicals. Direct dyes are defined as anionic dyes with substantively for cellulosic fibres, normally applied from an aqueous dye bath containing an electrolyte, either sodium chloride (NaCl) or sodium sulphate (Na2SO4).
Nature of Sample : 100% cotton pre-treated knit fabric.
Apparatus Required :
1. Beakers.
2. Glass Rod.
3. Pipette.
4. Measuring Cylinder.
5. Digital Balance.
6. Tri-pod Stand.
7. Gas burner.
8. Thermometer.'
9. Pot.
Process Sequence:
Collection of 100% cotton pre treated sample
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Dyeing with direct dye at 100deg C for 20 Minutes
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After Treatment
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cold rinsing
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hot wash
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cold rinsing
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drying
Recipe:
Direct Dye: 1% Owf (Stock Solution - 1%)
Wetting Agent: 1 g/L (Stock Solution - 1%)
Salt: 2 g/L (Stock Solution - 2%)
Soda Ash :1 g/L (Stock Solution - 1%)
Temperature:100deg C
Time: 20 minutes
Fabric Weight: 5gm
M:L = 1:30
Calculation:
Total Liquor required
Fabric Weight = 5gm
M: L = 1:30
Required amount of liquor = 5 X 30
= 150mL
Direct Dye :
= (5 X 1%) / (1%)
= 5ml
Salt : 1g/L
= (150 X 1g/L) / (1% x 1000)
= 15ml
Soda ash: 1g/L
= (150 X 1g/L) / (1% x 1000)
= 15ml
Wetting Agent : 1g/L
= (150 X 1g/L) / (1% x 1000)
= 15ml
Initial Water required = Total liquor - Chemicals
= 150 - (15+5+15+15)
= 150-50 mL
= 100 mL
Function of Chemicals:
Direct Dye: the primary chemical substance use to color the fabric.
NaCl: This common slat used as electrolyte. We know that direct dye is anionic dye and cotton fibre assume a negative charge when immersed in water. Electrolyte reduce or extinguish the charge on the fibre, to color the fabric.
Soda Ash:
It Maintain suitable pH for direct dyeing.
Wetting Agent:
wetting agent is substances that reduce the surface tension of water to allow it to spread drops onto a surface, increasing the spreading abilities of a liquid. Lowering the surface tension lowers the energy required to spread drops onto a film.
Process Curve:
Fig: Sample Before Dyed
Fig: Sample After Dyed
Comments:
The pre-treated Fabric absorbed direct dye.
Pre-cautions:
- All chemicals measure are taken properly.
- Temperature maintain properly.
- Burner used very carefully.
- Time maintain according to recipe.
Conclusion:.....................................
