Sulphur Dyeing Process in the Lab

In this article, we are going to know about the dyeing process of cotton fabric with sulphur dye. Sulphur is insoluble in water. So the process is different from other dyeing processes. We have done this procedure in the chemical lab live and described here the whole process. So let's get started.

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Theory

Sulphur dye is a water-insoluble dye. It needs to be water-soluble before a reducing agent is used to make it soluble for dyeing. In the final stage, the fabric needs to be insoluble again through the chemical oxidation process. Generally, potassium or sodium dichromate is used for oxidation. Then the fabric is washed off with detergent to remove the unfixed dyes.

Recipe

Dyeing
Sulphur red8% (owf)
Na2S8 g/L
Glauber salt10 g/L
Soda ash3 g/L
Wetting agent1 g/L
Leveling agent1 g/L
Sequestering agent1 g/L
Temp ✕ Time85℃ ✕ 50 mins
pH10
M:L1:40
Sample weight10 gm
Oxidation
K2Cr2O72 g/L
Temp ✕ Time50℃ ✕ 10 mins
Neutralization
Acetic acid1 g/L
Temp ✕ Time50℃ ✕ 10 mins
Soaping
Detergent1 g/L
Temp ✕ Time70℃ ✕ 10 mins

Functions of the Chemicals Required

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

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

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

Reducing agent: The chemical compound which losses electrons during the chemical reaction. It reduces other substrates chemically.

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

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

Oxidizing agent: An oxidizing agent is a substance that has the ability to oxidize other substances. It undergoes a chemical reaction in which it gains or accepts one or more electrons.

Acetic acid: Its function is to control pH in the process.

Detergent: For emulsifying fats, oils, and waxes. Removes the unfixed dyes from the surface of the fabric.

Recipe Calculation

Here, M: L= 1:40 
Sample weight: 10 gm

Total liquor: (10✕40)= 400 ml

Chemicals= (g/L ✕ Total liquor)/1000

Na2S= (8✕400)/1000= 3.2 gm
Soda ash= (3✕400)/1000= 1.2 gm
Glauber salt= (10✕400)/1000= 4 gm
Wetting agent= (1✕400)/1000= 0.4 ml
Leveling agent= 0.4 ml
Sequestering agent= 0.4 gm

Total= (0.4+0.4)= 0.8 ml

Shade Attachment

Sulfur Dyed Cotton Sample
Sulphur Dyed Cotton Sample

©Textile Pad


Dyeing Curve

Sulfur Dyeing Curve
Sulphur Dyeing Curve

©Textile Pad


Conclusion

Sulphur dyes are inexpensive, generally have good wash-fastness, and are easy to apply. They are predominantly black, brown, and dark. Recent advances in dyeing technologies have allowed the substitution of toxic sulfide-reducing agents. Future developments in the field of reducing dye levels by means of electrochemical processes are promising.

Bijoy

Studied In Textile Engineering. Likes writing and reading articles on the internet. Likes to take on new challenges and is interested in learning new machinery items.facebooklinkedin

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