The process of applying a protective adhesive coating on the surface of the yarn
is called sizing.

  1. Increase in Breaking Strength:
    • Sizing creates bonds between fibers, boosting yarn strength by 20 to 40%.
  2. Increase in Abrasion Resistance:
    • The gap between fibers is filled with sizing material, forming a protective coating on the yarn’s outer surface, enhancing abrasion resistance.
  3. Increase in Stiffness:
    • Sizing reduces yarn flexibility, making it less pliable and increasing stiffness.
  4. Increase in Elasticity:
    • Sized yarns are less extensible, requiring more force for stretching, resulting in increased elasticity.
  5. Increase in Frictional Resistance:
    • Applying sizing materials smoothens the outer surface, reducing friction between yarns.
  6. Increase in Yarn Diameter:
    • Sizing involves coating the outer surface, leading to an increase in yarn diameter.
  7. Decrease in Extension:
    • Sizing fills gaps between fibers, preventing easy slippage and decreasing yarn extension.
  8. Decrease in Electrostatic Charge:
    • Sizing materials contain moisture, reducing static friction and minimizing the formation of electrostatic charges.
  9. Decrease in Hairiness:
    • Sizing fixes protruding fibers to the yarn, reducing hairiness

The ingredients used in sizing and their functions in simple terms:

  1. Adhesive:
    • Types: Natural (from maize, corn, potato) or Synthetic (CMC, PVC, PVA).
    • Function:
      • Coats yarn for protection.
      • Improves strength.
      • Enhances smoothness.
      • Increases elasticity and stiffness.
  2. Lubricant or Softener:
    • Examples: Japan wax, tallow, linseed oil, coconut oil.
    • Function:
      • Makes yarn soft and slippery.
      • Smoothens the yarn.
      • Reduces stiffness.
  3. Antiseptic or Anti-mildew Agent:
    • Examples: Carboxylic acid, salicylic acid, ZnCl2, phenol.
    • Function:
      • Prevents mildew formation.
      • Preserves size material.
      • Protects yarn from bacteria or fungus.
  4. Anti-static Agent:
    • Reduces static electricity on the yarn’s surface.
  5. Hygroscopic Agents:
    • Examples: Magnesium chloride, calcium chloride, glycerin.
    • Function:
      • Moisturizes the yarn.
      • Prevents excessive drying.
  6. Weighting Agent:
    • Examples: China clay, sodium sulfate, French chalk.
    • Function:
      • Increases yarn weight.
      • Imparts fullness and feel to the fabric.
  7. Antifoaming Agent:
    • Examples: Silicon-based defoamer, water-insoluble esters.
    • Function:
      • Prevents foam formation during cooking.
      • Ensures uniform size application.
  8. Wetting Agent:
    • Examples: Sulphanol A, soap, avirol, alizarine oil.
    • Function:
      • Increases wetting ability of the sizing solution.
      • Reduces surface tension for better penetration and distribution on yarn.
  9. Tin-tin Agents:
    • Used to increase the luster of the yarn.

Types of sizing:

Sizing TypePick-Up PercentagePurpose
Pure Sizing7%Used to significantly increase weight and stiffness of the fabric.
Light Sizing8-11%Imparts special feel or handle properties.
Medium Sizing12-15%Facilitates weaving and increases fabric weight.
Heavy Sizing16-40%Used to significantly increase the weight and stiffness of the fabric.

Sizing techniques used in textile manufacturing:

  1. Conventional/Slasher Sizing:
    • Process: Applying material on yarn at 600°C, drying, separating, and winding.
    • Widely used method.
    • 90% weight increase in material.
  2. Hot Melt Sizing:
    • Process: Applying molten material on yarn through heated grooves.
    • No need for solidification heating.
    • No water used.
    • No size box required.
  3. High Pressure Sizing:
    • Process: Applying concentrated material with high pressure.
    • Saves 22% energy.
    • Higher production rate.
    • Used for sectional warping.
    • 20-30 times higher pressure than conventional sizing.
  4. Foam Sizing:
    • Process: Using foam-like material on yarn.
    • Lower material pickup.
    • Lower water evaporation.
    • Saves energy.
    • Higher production.
  5. Solvent Sizing/Slashing:
    • Process: Using non-water solvent for material preparation.
    • Applied at room temperature.
    • Closed chamber drying.
    • Solvents collected for recycling.
    • Lower production cost.
  6. Electrostatic Sizing:
    • Process: Warp sheet wetted in a salt solution, then coated with charged particles.
    • Controlled pickup.
    • Coated warp passes through infrared heater for fusion.
    • Cooling chamber.
  7. Polymer Emulsion Sizing:
    • Process: Using concentrated polymeric material in emulsion.
    • Lower weight pickup (30-50%).
    • High-pressure squeezing.
    • Heating for fusion.
    • Saves energy.
    • Higher production.

Methods of drying:

Drying MethodDescription
Cylinder Dryinga. Two Cylinder: Conventional drying with one large and one small cylinder.
b. Multiple Cylinder (Odd or Even): First two or four cylinders are Teflon coated with high steam pressure.
Hot Air DryingDrying using hot air.
Infra-Red DryingDrying with infra-red technology.
Combined DryingCombination of cylinder and hot air drying methods.

Analysis of weaving performance of sized yarn:

  1. Best Weaving Performance:
    • Higher breaking strength combined with increased extension at break results in optimal weaving performance.
  2. Reduced Tensile Force:
    • The estimated tensile force on a warp yarn is only 20% of the breaking strength of unsized yarn.
  3. Fewer Extensions, Fewer Breaks:
    • Yarns with fewer extensions experience fewer breaks during weaving.
  4. Size Film Issues:
    • Cracking and dropping of the size film can create local stress, encouraging end breaks during weaving.
  5. Increased Yarn Diameter:
    • The increased diameter of sized yarn leads to higher inter-yarn friction, contributing to potential breakage.
  6. Reduced Yarn Hairiness:
    • Decreased yarn hairiness improves weavability.
  7. Effect of Humidity:
    • Weaving under any humidity conditions increases the occurrence of short hairs (less than 0.2mm) to the level observed in unsized yarn.

Shirley Automatic Size Box:

The Shirley Automatic Size Box is designed to overcome the challenge of maintaining a consistent concentration of size solution in traditional size boxes. Its main objectives are to ensure a constant level of size solution and a steady concentration per volume.

The Shirley Automatic Size Box is essentially a container holding the size solution. It includes an immersion roller for dipping warp yarn into the solution and a squeezing roller to control the percentage of size take-up. Two separate pipes, a water pipe, and a size solution pipe, regulate the volume and concentration of the size liquor in the box.

Basic Principle:
The system operates by adding the necessary amount of water through a water pipe and size liquor solution through another pipe into the size box. The key principle is that if the concentration of the size solution increases, water is automatically introduced from the water pipe to maintain the desired concentration. Conversely, if the concentration decreases, size solution is automatically supplied from the size ingredient pipe, ensuring both concentration and volume remain constant.

The yarn sheet is guided to the immersion roller via a guide roller and then passes through the squeezing and sizing roller. The pressure applied by the squeezing roller controls the percentage of yarn size take-up.

Considerations for choosing size ingredients:

  1. Minimize End Breakage:
    • Choose a recipe that minimizes the occurrence of end breakage during the sizing process.
  2. Reduce Exfoliation:
    • Opt for ingredients that result in minimal exfoliation, ensuring the stability of the sized yarn.
  3. Easy Desizing:
    • Select ingredients that permit easy desizing, facilitating the removal of size from the yarn.
  4. Enhance Fabric Characteristics:
    • The chosen size ingredients should contribute to good fabric characteristics, ensuring the desired properties in the final product.
  5. Compatibility with Machinery:
    • Ensure that the size ingredients are compatible with the machinery and associated parts used in the sizing process.
  6. No Health Hazards:
    • Prioritize ingredients that do not pose any health hazards to those involved in the manufacturing process.
  7. No Material Degradation:
    • The size ingredients should not cause any degradation of the textile material, preserving its quality.
  8. Cost-Effective:
    • Opt for ingredients that are economical, considering cost-effectiveness in the overall sizing process.
  9. Neutral Properties:
    • Size ingredients should be neutral, meaning they do not adversely affect the yarn or the subsequent processes in the textile manufacturing.

Disadvantages of sizing:

  1. Additional Capital Investment:
    • Sizing requires additional capital investment for the unit setup.
  2. Longer Process:
    • The sizing process takes longer, impacting overall production time.
  3. Extra Cost of Ingredients:
    • There’s an additional cost for sizing ingredients used in the process.
  4. Extra Cost for Utilities:
    • Increased utility costs are incurred during sizing.
  5. Extra Labor Cost:
    • Additional labor is needed, contributing to higher operational costs.
  6. Possibility of Yarn Deterioration:
    • Yarn quality may be compromised due to handling during the sizing process.
  7. Increased Yarn Diameter:
    • The increase in yarn diameter limits the accumulation of more ends per inch.
  8. Rough Yarn Surface:
    • Sizing may result in a rough yarn surface.
  9. Reduction in Extension:
    • Sizing leads to a reduction in yarn extension.
  10. Increase in Stiffness:
    • The yarn may become stiffer after sizing.
  11. Generation of Fluff:
    • Fluff generation is a potential issue during sizing.
  12. More Robust Loom:
    • A more robust loom may be required to handle sized yarn.
  13. More Power Requirement:
    • Additional power is needed, particularly in the form of steam.
  14. Shorter Warp Length:
    • Sizing may limit the length of the warp.
  15. Problem of Size Removal:
    • Removing the size from the yarn can pose challenges.
  16. Risk of Uneven Shed:
    • There’s a risk of uneven shed formation during weaving.
  17. Extra Cost for Sizing:
    • There’s an additional cost associated with the sizing process.
  18. Additional Information Needed:
    • More information about ingredients is required before sizing.
  19. Environmental Pollution:
    • The sizing process may contribute to environmental pollution.
  20. Color Fading of Dyed Warp:
    • Dyed warp may experience color fading due to sizing.

Attempts made to substitute sizing in weaving:

  1. High-Quality Warp Yarn:
    • Use very high-quality warp yarn, made from longer and uniformly lengthed staples, allowing for weaving at low speeds. Combed yarn can be an option.
  2. Wrapped Yarn:
    • Utilize wrapped yarn, similar to core-spun yarn, which enables weaving without the need for sizing.
  3. Twisted Yarn:
    • Employ twisted yarn, which provides strength and allows for high-speed weaving without sizing. This type of yarn is a kind of ply yarn.
  4. Singed Yarn:
    • Perform singeing during warping, especially on dyed yarn. After dyeing, singeing is done to remove yarn hairiness, making it suitable for weaving.
  5. Heat-Setted Yarn:
    • Use heat-setted yarn, particularly synthetic and blends of synthetic and natural fibers, to eliminate the need for sizing.
  6. Modification of Loom Mechanism:
    • Modify the loom mechanism by reducing the length of the shed. This allows weaving without sizing. For instance, if the weaving zone length is reduced, the high stress on the warp is minimized, enabling weaving without the need for sizing. Adjusting the shedding length can reduce the force acting on the warp, making sizing unnecessary.

Sizing Faults:

  1. Sizing Spots:
    • Cause: The size ingredients should not be added all at once; they should be added gradually to prevent the formation of size spots on the yarn.
  2. Shinnery:
    • Cause: This defect is caused by the friction between the drying cylinder and the warp yarn during the sizing process.
  3. Sandy Warp:
    • Cause: Improper mixing, crushing, or grinding of size ingredients leads to the formation of sandy warp.
  4. Ridge Beam:
    • Cause: Uneven distribution of yarn on the beam results in the occurrence of ridge beams.
  5. Repeating Warp Streaks:
    • Cause: Uneven tension in the beam causes repeating warp streaks during sizing.
  6. Size Dropping:
    • Cause: Improper viscosity of the size mix leads to the dropping of size during the sizing process.
  7. Size Stitching:
    • Cause: Caused by improper drying after sizing.
  8. Hard Sizing:
    • Cause: Size becomes too hard when excessive size materials are applied, leading to hard sizing. Over drying can also contribute to hard sizing.
  9. Bacteria Formation, Yarn Breakage:
    • Cause: Under drying of yarn can lead to bacteria formation and yarn breakage.
  10. Uneven Sizing:
    • Cause: Caused by over-drying or under-concentration of size liquor during the sizing process.

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