Reactive Dyeing of Cotton in the Lab

SohaniSharma

Theory

Reactive dyeing is the most important method for the coloration of cellulose fibers. Reactive dyes have a low utilization degree compared to other dyestuffs, since the functional group also bonds to water, creating hydrolysis. Reactive dyes react with the fabric in the presence of alkali and adhere as a part of the fiber.

The three main mechanisms of reactive dyeing are exhaustion, fixation, and finally washing off. First, exhaustion happens in the presence of electrolytes. Then fixation happened under the influence of alkali. Finally, wash off the fabric to remove unfixed dye from the material surface. Softeners can be used to soften the surface of the fabric. Thus, the total reactive dyeing process is done.

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Functions of the Chemicals Required

Wetting agent: It accelerates the wettability of material in solution, thus helping to easy penetration of the chemicals into the substrate. It reduces the surface tension of water to allow it to spread as drops on a surface, increasing the spreading abilities of a liquid.

Sequestering agent: A sequestering agent is a substance that suppresses the property or reaction of metal ions without the removal of that metal from the system.

Leveling agent: Leveling agent tends to slow down the dye uptake on the fibers, helping to produce a more uniform color in the textile fiber.

Common salt: Salt is used as an electrolyte. This electrolyte neutralizes the negative charge formed on the fiber surface and adds extra energy to increase dye absorption.

Soda ash: Soda ash creates the proper pH in the dye bath and acts as the dye-fixing agent. This helps in forming a strong covalent bond between the dye and the fabric.

Recipes

Light shade (0-0.5%)	Medium shade (0.5-1%)	Deep shade (1.1-2%)
Reactive Red = 0.20%	Reactive Red = 0.40%	Reactive Red = 0.60%
Reactive Blue = 0.10%	Reactive Blue = 0.20%	Reactive Blue = 0.40%
Reactive Yellow = 0.20%	Reactive Yellow = 0.40%	Reactive Yellow = 0.80%
Total = 0.5%	Total= 1%	Total = 1.80%
Glauber salt= 20 g/L	Glauber salt= 40 g/L	Glauber salt= 60 g/L
Soda ash= 8 g/L	Soda ash= 14 g/L	Soda ash= 20 g/L
Common Chemicals Wetting agent= 1 g/L Sequestering agent= 1g/L Leveling agent= 1 g/L M: L= 1:20 pH = 10 -11 Sample weight = 5 gm Total liquor = 100 ml Temperature ✕ Time= 60℃ ✕ 60 minutes

Recipe Calculation

Here, M: L= 1:20

Sample weight: 5 gm

Total liquor: 5 ✕ 20= 100 ml

For light shade;

Dye= (Shade% ✕ Fabric weight) / Stock solution%

Reactive Red= (0.20% ✕ 5) / 1%= 1 ml

Reactive Blue = (0.10% ✕ 5) /1% = 0.5 ml

Reactive Yellow = (0.10% ✕ 5) /1% = 0.5 ml

Chemicals= (g/L ✕ Total liquor) /1000

Glauber's salt = (20 ✕ 100) /1000= 2 gm

Soda ash = (8 ✕ 100) /1000= 0.8 gm

Wetting agent = (1 ✕ 100) /1000= 0.1 ml

Leveling agent = 0.1 ml

Sequestering agent = 0.1 gm

Total = (1+ 0.5 + 1+ 0.1 + 0.1)= 2.7 ml

Freshwater = (100 – 2.7) = 97.3 ml

For medium shade;

Dye= (Shade% ✕ Fabric weight) / Sock solution%

Reactive Red = (0.40% ✕ 5) / 1% = 2 ml

Reactive Blue = (0.20% ✕ 5) / 1% = 1 ml

Reactive Yellow = (0.40% ✕ 5) / 1%= 2 ml

Chemicals= (g/L ✕ Total liquor) / 1000

Glauber's salt= 40 ✕ 100) /1000 = 4 gm

Soda ash = (14 ✕ 100) /1000= 1.4 gm

Wetting agent = (1 ✕ 100) /1000= 0.1 ml

Leveling agent = 0.1 ml

Sequestering agent = 0.1 gm

Total = (2 + 1 + 2 + 0.1 + 0.1) = 5.2 ml

Freshwater= (100 – 5.2)= 94.8 ml

For deep shade;

Dye= (Shade% ✕ Fabric weight) / Sock solution%

Reactive red= (0.60% ✕ 5) /1%= 3 ml

Reactive blue= (0.40% ✕ 5) /1%= 2 ml

Reactive yellow = (0.80% ✕ 5) /1%= 4 ml

Chemicals= (g/L ✕ Total liquor) / 1000

Glauber's salt = (60 ✕ 100) / 1000 = 6 gm

Soda ash = (20 ✕ 100) / 1000= 2 gm

Wetting agent = (1 ✕ 100) / 1000= 0.1 ml

Leveling agent = 0.1 ml

Sequestering agent = 0.1 gm

Total = (3 + 2 + 4 + 0.1 + 0.1)= 9.2 ml

Freshwater = (100 – 9.2) = 90.8 ml

Shade Attachment

Reactive Dyed Fabric Samples

Dyeing Curve

Reactive Dyeing Curve

Conclusion

Reactive dyeing is becoming very popular for fabric coloration because of some specific properties like a wide range of shades, reproducibility, good fastness, and a simple application procedure.

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