Sizing is a process to applying a protective adhesive coating upon the surface of yarns which is known as Sizing.
Objectives of Sizing:
1. For improving the yarn weave ability.
2. To maintain good fabric quality.
3. To increase yarn elasticity.
4. To increase the yarn weight.
5. To increase the frictional resistance.
6. To reduce the fibers projection.
7. To increase the breaking strength.
8. To increase stiffness.
9. To control irregularity of yarn.
10. To reduce electrostatic charge.
11. To make the weak or less strength yarn suitable for weaving.
Requirements of sizing: The requirements of sizing are given below which is ensured good technological properties of sized warps,
1. Sized warp must be sufficiently smooth, strong and elastic.
2. The application of the required amount of size on the yarn must be ensured by sizing process.
3. Admitted limits should be within the yarn loss and stretch in elongation.
4. Weavers beam must be cylindrical shaped and also produced necessary winding density and the yarn length.
5. High quality sized warp production must be ensured.
6. Sizing process must be economical and efficient.
Technological changes due to Sizing: The technological changes due to sizing is given below,
1. Increasing in breaking strength: Up to 20-40% breaking strength increased due to inter fiber bonding system.
2. Increase abrasion resistance: The gaps between fibers are filled with coating and size on the outer surface after sizing.
3. Increase in stiffness: Stiffness of yarn is increased in sizing process.
4. Increase in elasticity: Extensibility of sized yarn decreased due to sizing and there applied more force to extent the yarn. Hence elasticity increased.
5. Decrease in extension: The gap between the fiber is filled by the size material ager sizing hence the slippage between the fibers does not take place that’s why extension is decreased.
6. Decrease in electrostatic charge: Electrostatic charge is formed due to friction between yarn and roller. But electrostatic charge is decreased due to application of size material.
7. Decrease yarn irregularity: Projecting fiber to adhere together are makes by sizing process. Hence yarn irregularity decreases.
Effects of sizing on yarn properties: The following properties of yarn are affected by sizing,
1. Yarn strength.
2. Flexibility of yarn.
3. Yarn elasticity.
4. Irregularity of yarn.
5. Yarn weight.
6. Yarn diameter.
7. Hairiness of yarn.
8. Smoothness of yarn.
Factors Considered before the selection of size ingredients: The factors considered before the selection of size ingredients are given below,
1. To the yarn its must be non-degrading.
2. It must be compatibility with equipment.
3. If necessary, it must be easily removal.
4. If not removed, its provides good fabric characteristics.
5. Least amount of dusting-off during weaving.
6. Cost of the ingredients must be less.
7. It should not modify the tone of colored warps.
8. Easily prepared.
9. Lack of odor.
10. No beam blocking.
11. Compatible with other ingredients.
12. No skimming tendency.
13. Neutral pH.
14. Insensitive to high heat.
15. Rapid drying.
Natural Sizing agents:
1. Natural substances and their derivatives the natural sizing agents are based on.
2. Starch and starch derivatives: degradation starch, native starch and chemical modified starch products.
3. Cellulosic derivatives: Oxyethyl cellulose, CMC and methyl cellulose.
4. Protein –based starch: Gelatin, albumen and glue.
Synthetic sizing agents:
1. Modified polyester.
2. Styrol or maleic acid copolymers.
3. Polyacrylates.
4. Polyvinyl alcohols.