Process Flow Chart of Yarn Sizing

Last Updated on 01/08/2024

What is Yarn Sizing?
Yarn sizing is the process of applying protective adhesive coating on the yarn surface and to lubricate the surface of the yarn to enable it to withstand the abrasive action which occurs in the weaving process. Sizing has the function of enhancing the mechanical properties and the loading capacity of the thread without reducing the thread elasticity. It also serves to reduce yarn hairiness.

yarn sizing
Fig: Yarn sizing

Sizing therefore improves the weavability of warp threads by reducing thread–thread and thread–metal friction. The efficiency of a size is measured by the weaving yield. Sizing is the most important segment of weaving preparatory process. Because sizing has direct influence on the weaving efficiency. Better the quality of sizing higher the weaving efficiency and vice versa. In fact without sizing, in most of the cases it is almost impossible to run the weaving process. Moreover in case of towel manufacturing rotor (open end) and low twisted yarns are mostly used.

The application of sizing material results in the following properties in yarn.

  • High strength
  • Low flexibility
  • Low abrasion
  • Increased smoothness
  • Less hairiness

Types of Yarn Sizing:
The sizing procedures can be divided according to groups of slashing products:

  1. Hot-melt sizing: Application of a melt-liquid, water-free bonding agent.
  2. Cold sizing: Application of a small amount of bonding agent at room temperature.
  3. Dry sizing: Application of a melt-liquid, water-free product without a sticky component.
  4. Wet sizing: Traditional wet sizing. Application of a water-soluble size followed by drying.
  5. Solvent sizing: Dissolved size remains on the warp after evaporation of the solvent.
  6. Warp waxing: Application of a liquid, water-containing product without a sticky component.

Sizing Requirements:

  • Reduction of friction
  • Good film formation
  • No skin formation
  • Water solubility (cold or hot water, hard water)
  • Low-costs.

Needs of Subsequent Processes:

  1. High weaving efficiency
  2. Stability to electrolytes and alkaline solutions
  3. Readily removable (desizing)
  4. Compatibility with other process steps (e.g., singeing/thermo fixation)
  5. Non-foaming (in the bath or on rollers)
  6. Ecological compatibility
  7. Identifiable on the fiber.

Main Characteristics of Sizes:
Sizing compounds and lubricants are applied to yarns before fabric formation to protect the integrity of the yarns. While increasingly faster weaving processes demand more enduring sizes, such as acrylic-based compounds, natural sizes that can be decomposed by enzymes are still on the market. Sizing materials has to fulfill certain requirements in sizing and subsequent process steps.

Flow Chart of Yarn Sizing:
Flow chart for the yarn sizing process involves outlining the steps taken to prepare yarn for weaving by coating it with a sizing agent. This process improves the yarn’s strength and reduces breakage during weaving. Below is a simplified flow chart of the yarn sizing process:

Size Cooking

Creeling

Yarn Feeding

Sizing (in show box)

Drying

Leasing

Denting

Empty Beam Feeding & M/C Running

Ends Cutting

Doffing

Inspection and Quality Control

Working Procedure of Conventional Sizing Machine:
The main parts of conventional sizing machine include creel, sizing box, drying section, leasing section, head stock and size cooker.

Schematic diagram of conventional wet sizing machine
Fig: Schematic diagram of conventional wet sizing machine

In conventional wet sizing, the fundamental constituents of size recipe are the size materials and a solvent usually water. The sizing materials are broadly classified into three groups namely adhesives, softeners and auxiliaries. The adhesives perform two functions; bind the constituent fibers of the yarn together and form a film over the yarn surface, resulting in increased strength, low hairiness and more even yarn. The adhesives are classified on the basis of origin into natural, synthetic and modified adhesives, produced by treating natural adhesives with certain chemicals. The natural adhesives may be obtained from plants or animals, for example maize starch, potato starch, etc. The chemical modification of natural adhesives is performed to induce the desired properties. Some common examples of modified adhesives are modified starches and carboxy methyl cellulose (CMC). The chemically synthesized polymers like poly vinyl alcohol (PVA) and acrylics fall under the category of synthetic adhesives. Starch adhesives are used most commonly because of low cost and environment safety.

The softeners are added in the size recipe to lubricate the yarn and reduce abrasion / friction between adjacent yarns and between yarns and loom accessories. They also give a soft handle to the warp and size film, helping to decrease its brittleness. The softeners may be in solid form (wax group) or liquid form (oil group) and are obtained from animals, vegetables or synthesized chemically. The auxiliaries include antiseptic, antistatic, weighting, swelling agents and / or defoamers. The sized fabric must be subjected to a desizing process prior to the finishing stage. Desizing has a decisive effect on the waste water load in textile production.

You may also like:

  1. Yarn Sizing: Important Warp Preparatory Process
  2. Parameters for the Process Control in Sizing of Warp Yarn
  3. Techniques of Warp Yarn Sizing in Weaving Preparatory Process

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