Warp is the set of lengthwise yarn through witch the weft is woven. In characteristic weave of denim, weft passes through two or more weft yarns to create traditional diagonal patron. Due to high tension and friction in weaving, there are healthy chances of warp breakage. Sizing material is applied as protecting glaze or lubricant. It is used to improve surface properties.
Sizing of the warp yarn is essential to reduce breakage of the yarn and thus production stops on the weaving machine. On the weaving machine, the warp yarns are subjected to several types of actions i.e. cyclic strain, flexing, abrasion at various loom parts and inter yarn friction.
With sizing the strength – abrasion resistance – of the yarn will improve and the hairiness of yarn will decrease. The degree of improvement of strength depends on adhesion force between fiber and size, size penetration as well as encapsulation of yarn.
Â Different types of water soluble polymers called textile sizing agents/chemicals such as modified starch, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), acrylates are used to protect the yarn. Also wax is added to reduce the abrasiveness of the warp yarns. The type of yarn material e.g. cotton, pol
yester, linnen, the thickness of the yarn, type of weaving machinery will determine the sizing recipe. The sizing liquor is applied on warp yarn with a warp sizing machine.
Iodine solution is used to test for starch; a blue color indicates the presence of starch. The details of this reaction are not yet fully known, but it is thought that the iodine (I3âˆ’ and I5âˆ’ ions) fits inside the coils of amylose, the charge transfers between the iodine and the starch, and the energy level spacings in the resulting complex correspond to the absorption spectrum in the visible light region. The strength of the resulting blue color depends on the amount of amylose present.