GREY FABRICS

Question 1

1. Which one is better bleaching process – hypochlorite or peroxide? Why?

Answer 1

• Peroxide is better bleaching
• Because of more whiteness, less damage, less time and combine scouring and bleaching process is possible.

Question 2

2. Why is grey cotton material hydrophobic?

Answer 2

Grey cotton fabric consists natural impurities like oils, wax, etc. and added impurities like starch so that grey cotton materials are hydrophobic.

Question 3

3. Write the properties of mercerized yarn.

Answer 3

• Improve Luster.
• Increase ability to absorb dye.
• Improve reaction with a verity of chemicals.
• Improve stability of form.
• Improve strength/elongation.
• Improve smoothness.

Question 4

4. State the objectives of scouring

Answer 4

• To make the fabric highly hydrophilic.
• To remove impurities such as oils, waxes, gum, husks as nearly as possible.
• To increase absorbency of fabric or textile materials without physical and chemical damage.
• To produce a clean material by adding alkali.
• To make the fabric ready for next process.
• To remove non-cellulosic substance in case of cotton

Question 5

5. Mention the advantages of enzyme desizing.

Answer 5

Advantages
* Time required for the desizing process is less.
* It is continuous process, so greater production can be achieved.

Disadvantages
* If the conditions of temperature, pH and time are not properly maintained, the desizing activity of the enzymes is destroyed.

Question 6

6. Which beaching agent is called as universal bleaching agents? Why it is called so?

Answer 6

• Hydrogen peroxide is called as universal bleaching agents.
• Because it is suitable for all kind of fibres

Question 7

7. A fabric is having traces of peroxide after bleaching. How to solve this problem?

Answer 7

• Using Peroxide killer treatment.
• To remove the traces of the peroxide content in bleached fabric using vigorous rinsing or using inorganic reducing agents

Question 8

8. Mention the change take place in cotton during scouring process.

Answer 8

. fatty acids are converted into soaps.
* Pectins and pectoses are converted into soluble salts of pectic acid.
* Proteins are degraded to simple soluble amino acids or ammonia.
* Additive dirts are removed.

Question 9

9. Why the bleaching agents used in textile industry are oxidizing agents and not used for reducing agents?

Answer 9

Oxidizing bleaching agents provide the permanent whiteness compare to reducing bleaching agents.

Question 10

10. What is the role of sodium silicate in scouring and bleaching?

Answer 10

In scouring: * To prevent the formation of iron stains in scoured fabric
In bleaching
* Act as stabilizer
* To maintain the pH during scouring and bleaching process

Question 11

11. Write the chemical used in scouring process.

Answer 11

Caustic soda
Surfactants
Detergents
Chelating agent
Sodium silicate
Soda ash

Question 12

12. List the objectives of Singeing

Answer 12

• To remove the projecting/protruding fibres coming out from the fabric/yarn structure.
• To obtain a clean a smooth surface.
• To increase the lustre of the fabric
  . to ready for printing process

Question 13

13. What are the objectives of Bleaching cotton fabric?

Answer 13

• To remove the natural and added colouring matters
• To make white