Dyeing of 100% Cotton Knitted Fabric with Direct Dye.

Experiment Name:  Dyeing of 100% cotton knitted fabric with direct dye.

Theory:  Direct Dye is a class of dyestuff that is 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. 

1. Direct dyes give bright shades but exhibit poor wash fastness. 

2. Various after treatments are used to improve the wash fastness of direct dyes.  

3. Direct Dyes are molecules that adhere to the fabric molecules without help from other chemicals. 

4. Direct dyes are defined as anionic dyes with substantively for cellulosic fibers, 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/ Order:

Collection of 100% cotton pre-treated sample

⇩

Dyeing with direct dye at 100deg C for 20 Minutes

⇩

After Treatment

⇩

cold rinsing

⇩

hot wash

⇩

cold rinsing

⇩

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%)
Leveling Agent	1g/L (Stock Solution - 1%)
Sequestering Agent	1g/L (Stock Solution - 1%)

Parameters:

1. Temperature:100deg C
2. Time: 20 minutes
3. Fabric Weight: 5gm
4. M:L =  1:30
5. ph=7-8

Calculation:

Total Liquor required

Fabric Weight = 5gm

M: L = 1:30

Required amount of liquor = 5 X 30

= 150mL

Direct Dye :

= (5X1%) / (1%)

= 5ml

Salt : 1g/L

= (150X1g/L) / (1%x1000)

= 15ml

Soda ash: 1g/L

= (150X1g/L) / (1%x1000)

= 15ml

Wetting Agent : 1g/L

= (150X1g/L) / (1%x1000)

= 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 used to color the fabric.

NaCl: This common salt is 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 Maintains suitable pH for direct dyeing.

Wetting Agent:

A wetting agent is a substance that reduces 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:

Sample Attachment and  Observation:

Fig: Sample Before Dyed

Fig: Sample After Dyed

Observation & Comments:

The pre-treated Fabric absorbed direct dye.

Pre-cautions:

• All chemical measures are taken properly.
• Temperature maintains properly.
• Burner used very carefully.
• Time is maintained according to recipe.