Manufacturing Process of Woollen Yarn

Flow Chart of Woollen Yarn Manufacturing

Why Cotton Shrinks

Why Cotton Shrinks

Cotton has the property of swelling in water and this effects shrinking when drying. Also the mechanical stresses, strain and tension, during spinning and weaving etc., when released causes the fabric to shrink.

The cotton fabric, when put in water, swelling occurs and rearrangement of internal forces takes place. The fibres will become free from tensionless state. These are the resons for shrinkage.

In case of a fabric, the warp yarns are under much strain due to interlacement than the weft yarns. The warp yarn shrinkage will be more than weft.

to overcome this, the fabric is extended in widthwise to some extent in the stenter machine during the finishing process. Then it is subjected to preshrink process.

How to Improve Colorfastness in Vat Dyeing

Colorfastness Problems in Vat Dyeing- Reasons and Remedies

Causes of Poor Colorfastness in Vat Dyeing

Frequent addition of colors in the dye bath to match the shade. It disturbs the equlibrium between colors and chemicals.

- Improper oxidation

- Improper washing

- Some peculiar colors such as blue and brown also leads to this defect.

- Hardness in the water used

- Mixing of incompatible colors

- Usage of large quantities of reducing agent and alkali

- Improper temperature

- Improper wringing of the cloth

- Faults in the machine

- Not using essential chemicals such as dispersing agent or leveling agents.

- Dyeing in a finished cloth ( Resin or Silicon Finish)

- Improper preparation of the cloth or thread for dyeing ( Like not removing impurities or size)

How to improve colorfastness in Vat Dyeing

1. Dont frequently add colors during dyeing

2. Ensure proper reduction clearance

3. Ensure proper oxidation

4. Choose right colors and chemicals

5. Control Temperarue

6. Use soft water

7. Add Dispersing or levelling agent as per need

8. Dont redye finished cloths

9. Ensure proper washing after dyeing.

10. Treat the material with small amount of Ammonia and Sodium Hydrosulphite

11. Treat the cloth with large amount of reducing agent and alkali. This method can be resorted to if there is some bleeding in the colors.

The Measures of Fiber Length

The Measures of Fiber Length

1. Mean Length: Numerical Average length of fibres of given population of fibre.

2. Upper Quartile: Length for which 75% of all observed values are lower or 25% higher by weight or number

3. Modal Length: The most frequently occuring length of fiber.

4. Median Length: Length Below and above which 50% of fibres lie.

5. Half Fall Value: The fiber length higher than modal length having half the modal frequency by wt. (Group length longer than mode with frequency equal to 1/2 of mode.)

6. Effective Length: Upper quartile of numerical length distribution from which some of the shortest fibers, having length less than half of effective length are cutailed or eliminated.

7. short fiber %: It is the % of fibers having length less than 1/2 of the effective length value.

8. Uniformity Ratio: Ratio of 50% span length to 2.5 % span length.

9. Span Length: It is the distance that can be spanned by specified percentage of fibers in a test beard.

10. Irregularity: Percentage by weight fo fibers in a sample which are shorter than 3/4th of the mode.

11. Dispersion %: inter quartile range expressed as % of effective length.