Sizing:
It is defined as the process of coating the yarn/warp sheets with the adhesive binder. Generally sizing is done to warp yarns to minimize the yarn breakages during the weaving process.
Objectives of Sizing:
To improve weavability of the warp or to overcome inherent deficiencies of the yarn to withstand the stresses and strains of weaving. This can be attained by improving primarily the abrasion resistance of the yarn. This in turn is achieved with the formation of a film around the yarn along with some penetration of sizing ingredients.
What sizing should do:
To improve the abrasion resistance of the yarn.
To reduce the hairiness of the yarn.
To reduce the generation of static charge for polyester blend yarns.
To improve the breaking strength of cellulosic yarns.
What sizing should not do:
Should not reduce the elongation-at-break of yarns below the norm.
Should not excessively increase missing ends and cross-ends.
Quality of sized beam:
A perfect sized beam should have:
Ends wound straight and parallel to each other, with no rolled, crossed, stuck, or loose ends.
Uniform tension from end to end.
Uniform warp density throughout the sized beam.
Selvage ends not high or low but flat with the warp.
Uniform applications of size.
Performance Assessment:
The real test of sizing lies in weaving. However, to check the performance of a sizing process, the following tests should be carried out:
Percent size add-on.
The moisture content of sized yarns.
Single yarn breaking strength and elongation-at-break.
Stretch on yarns during sizing.
Lappers and migration of ends.
Droppings at looms.
Invisible loss of sizing ingredients.
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