What is Sizing Dropping? Sizing dropping (also called shedding or fiber drop) happens when the sizing agent or fibers fall off the yarn during the sizing process. This affects fabric quality, and textile mills often test for the amount of dropping to improve production.
1. Causes of Sizing Dropping
- Poor Adhesion of Sizing Material: If the adhesive bond between the sizing material and the yarn is weak, the sizing can peel off during drying. For example, pure polyester yarns sized with PVA and starch often show severe drops because these agents don’t bond well with polyester.
- Surface Sizing or Over-Sizing: Even if the sizing material bonds well, too much sizing or only surface application causes the material to sit on top of the yarn without proper penetration. This leads to more shedding during the drying process.
- Low Moisture Content in Yarn: If the yarn is too dry, the sizing layer becomes brittle and breaks easily. This happens more often with starch-based sizing agents, which are more prone to cracking.
- Improper Dry Splitting Setup: Poorly set drying rollers or improper drying tension can increase friction between yarn layers. This leads to more shedding due to added stress on the yarn surface.
2. How to Reduce Sizing Dropping
- Choose the Right Sizing Agent: The sizing agent should match the fiber type, providing good adhesion and film strength. For example, water-soluble polyester used on polyester yarns bonds well and reduces shedding.
- Avoid Over-Sizing: Proper sizing should ensure that the agent penetrates into the yarn and doesn’t just cover its surface. Controlling the amount of sizing prevents excess buildup and reduces shedding.
- Maintain Proper Yarn Moisture Content: A dry yarn makes the sizing brittle and increases shedding. To prevent this, consider:
- Option 1: Automatically close steam valves and moisture fans when the machine slows down to keep humidity high.
- Option 2: Spray mist over the yarn when running the machine below 5 meters/minute to keep it moist and avoid brittleness.
- Optimize Dry Splitting Settings: Using a symmetrical splitting system or tension-balanced splitting reduces friction between yarn layers. For example, using a three-layer, parallel splitting system ensures equal tension across the yarn and minimizes shedding.
Conclusion:
- The main reason for sizing shedding is poor bonding between the sizing material and the yarn.
- Over-sizing or low moisture levels also contribute to this issue.
- To reduce shedding, choose the right sizing agent, control the amount of sizing, and keep the yarn’s moisture content and splitting settings optimized.
