Sizing is called the heart of weaving. Sizing is the process by which a protective adhesive coating is applies on a yarn surface. It increases the efficiency of weaving process.
Types of sizing: Sizing process is classified as follow:
- Pure Sizing: Application of size ingredients up to 10%.
- Light Sizing: Application of size ingredients 11% to 15%.
- Medium Sizing: Application of size ingredients 16% to 20%.
- Heavy Sizing: Application of size ingredients above 40%.
Types of sizing application methods or techniques: There are different application processes by which size materials are applied on yarn surface. Followings are the application methods.
- Hot melting sizing
- Solvent sizing
- Foam sizing
- High pressure sizing
- Electrostatic sizing
- Emulsion sizing
- Combined sizing
- Slasher sizing
Drying system: After application of size materials on yarn surface, it needs to dry to fix the size on the yarn. Following are the drying system.
- Two cylinder drying
- Multi cylinder drying
- Hot air drying
- Infrared drying
- Combined drying
Technical changes due to sizing: After application of size ingredients on the yarn surface, following changes are occurred. They are:
- Increase in breaking strength.
- Increase stiffness.
- Increase abrasion resistance.
- Increase elasticity.
- Increase smoothness.
- Increase actual diameter, but decrease apparent diameter.
- Decrease in hairiness.
- Decrease in extension.
- Decrease elastistatic charge.
Sizing is done during beam preparation. If sizing is done perfectly then it is possible to get a good qualified woven fabric.
So, we should be careful about the application of the sizing and its drying system.
Sizing is important for weaving but if the process does not done with proper accuracy then every things will be hampered. For this reason a textile engineer should be very careful during sizing operation. Sizing is done for grey or stripped fabric production. In denim; sizing is done after scouring, bleaching and dyeing process.
Requirements of sizing: A sizing process should fulfill the following requirements, which is important for fabric production.
- Sized warp must be sufficiently strong, smooth and elastic.
- The sizing process must ensure the application of the required amount of size on the yarn or the required size regain.
- The tension of warp yarn at sizing must be regular and constant all the time of warp unwinding from warp beam.
- Yarn strength and loss in elongation should be admitted limits.
- The package, i.e. the weavers beam produced must have cylindrical shape, necessary winding density and yarn strength.
- The sizing process must be efficient, economical and must ensure the production of high quality sized warp.
Choice of size ingredients: Different size ingredients have different characteristics which I have given in one of my blog. Choice of size ingredients are given below:
- The recipe should give the fewest breakage during weaving.
- It should give least amount of exfoliation.
- It should permit easy size removal in later operation.
- It should give good fabric characteristics.
- The recipe should be compatible with the machinery.
- The recipe should not cause any health hazard.
- The recipe should not cause any degradation of textile materials.
- It should be cheap but not necessarily.
- PH should lie between 7 to 7.4.
So, that’s all about requirements of sizing and choice of size ingredients.
Sizing is called heart of weaving. The materials which are used for sizing that is called size ingredients. A gelatinous film forming substance in solution or dispersion applied normally used for warp yarn but sometimes used for weft yarn before weaving is called size.
Size ingredients and their functions: Different types of sized ingredients are used for sizing. Followings are the main size ingredients used for sizing.
- Adhesive: Generally starch of maize, corn, rice, potato and CMC, PVC are used as adhesive. Tamarine is used as adhesive on jute yarn, the adhesive is in granule form that is mixed with water and heated to form a paste which ultimately becomes viscose fluid.
- To increase strength.
- To impart adhesion making the yarn less hairy.
- To increase abrasion resistance.
- To increase smoothness.
- To increase elasticity a stiffness.
- To reduce extensibility.
- Lubricants/Softener: Japan wax, Tallow, Mineral waxes, Vegetable waxes, Animal fats, Mineral oils and Vegetables are used as lubricants.
- It makes the yarn soft and slippery.
- It reduces stiffness.
- It increases yarn smoothness.
- It increases elasticity.
- Anti septic or anti mildew agent: Salicylic acid, Carbolic acid, Zinc chloride, Phenol is used as anti septic agent.
- It prevents mildew formation.
- To preserve size materials for a long time.
- It helps to store the yarn for a long time.
- To protect yarn from bacteria or fungus.
- Deliquescent or hydroscopic agent: Glycerin, Calcium chloride are used as deliquescent agent. Deliquescent agent is those substances which absorb moisture from air.
- It prevents excess drying of yarn.
- It helps to absorb moisture from air.
- To prevent the brittleness of size.
- Weighting agent: China clay, Sodium phosphate are used as weighting agent. These are used especially for those fabric or yarn that is to be solid or grey state.
- It increases the weight of yarn.
- To impart fullness and fell to the fabric.
- Anti foaming agent: Pyridine, Benzene are used as anti foaming agent.
Function: To prevent foam formation.
- Tinting agent: Blue is used as tinting agent.
Function: To increase lusture or brightness.
- Wetting agent: Sulphanol A, soap, avirol, magnesium chloride are used as wetting agent. The drawback of these substances is their high foaming ability and the foam is very stable.
- It increases size exhaust.
- To obtain a uniform distribution of sizing solution on yarn surface.
- It helps to wet yarn instantly.
So, when we will choose size ingredient for sizing we should remember the functions of size ingredients. Various dyes and chemicals manufacturing companies produce size ingredients, choose your favorite one from there.