Preparation of Cotton Fabric by Scouring

Name of the experiment: Preparation of cotton fabric by scouring

Introduction:
Scouring is a process by which all natural and adventitious impurities such as oil, wax fat etc are removed to produced hydrophilic and clean textile material specially cotton. Scouring is a preparatory process of cotton fabric for dyeing and finishing. These impurities hinder the penetration of dyes and chemicals to the interior of the fibres, so that the wastages of dyes and chemicals are increased and improper scouring creates the uneven dyeing. It is the vital process of wet processing.

Principle:

1. To remove non-cellulosic substance in the case of cotton.
2. To increase the absorbency of the fabric or textile materials without undergoing physical and chemical damage.
3. To make the fabric highly hydrophilic.
4. To produced a clean material by adding alkali.
5. To remove impurities such as oils, waxes, gum, husks as completely as possible.
6. To make the fabric ready for the next process.

Theory:
Scouring method of cotton is classified into main two groups; one is kier boiling process and other is scouring in J or L box.

In our laboratory we apply batch process. By this process the natural impurities of cellulosic fibres are normally removed by boiling off in a strong alkali solution. Alkali (caustic & soda ash) treatment with auxiliaries at high temperature removes the inherent and added impurities from cotton and other cellulosic fibres such as hemp, ramie, kenaf, linen, jute. Although all cellulosic fibres treatments are  Similar but the concentration of the alkalis and process parameter should be adjusted according to composing amount and structure of impurities. Due to removal of these impurities including oils and waxes the goods become more absorbent.

Parameter: 

• pH range: 10.5-11
• Duration of the treatment:1.30 hour
• Temparature: 65-90ºC
• M:L> 1:50

Recipe:

• NaOH: 3%
• Na₂CO₃: 3%
• Wetting agent: 1%
• Sequestering agent: 1%
• Detergent: 1%

Recipe calculation:

1. Weight of the fabric: 30 gm
2. Weight of the liquid: 30*50gm = 1500gm ≈ 1500cc
3. Wetting agent: (1*1500)\1000gm =1.50gm ≈ 1.50cc
4. Sequestering agent: (1*1500)\1000gm = 1.50 gm ≈ 1.50cc
5. Detergent: (1*1500)\1000gm = 1.50 gm ≈ 1.50cc
6. NaOH: (3*1500)\1000gm = 4.50 gm ≈ 4.50cc
7. Na₂CO₃: (3*1500)\1000gm = 4.50 gm

These values are calculated on the basis of the weight of the liquid.

Chemicals and its function:

Apparatus:

1. Beaker
2. Glass rod
3. Measuring Flasks
4. Bowl
5. pH meter
6. Burner
7. Thermometer

Procedure:

1. Set the bath substrate at room temperature with wetting agent, sequestering agent and detergent.
2. Add Alkali and raise the temperature to 90-95⁰C.
3. Run the bath for 1.30 hours
4. Cool down the bath temperature
5. Rinse twice with hot and cold water.
6. Neutralize with acetic acid (if needed) and carried for the next process.

Confirmation test:
Successful scouring ensures the better dye absorption into cotton fiber. It can be assessed in different ways. In practice, estimation of scouring effect can be carried out one of the following tests: measurements of weight lost, absorbency test, measurements of methylene blue absorption, measurements of copper number, measurements of protein content, and measurements of wax content.

In our laboratory we apply the measurements of weight lost process for the confirmation test.

Test: %weight loss of the sample = {(sample weight before scouring-sample weight after scouring) / sample weight before scouring}*100

Results:
The standard weight loss scoured cotton fabric is 4-8%. If the percentage is less than 4% it mentioned that it is not well scoured on the hand if it is up to 8%, it said the fabric is damaged due to over scoured. Both results are not accepted. In our laboratory the weight loss percentages is about            %.

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