De- Sizing is done on woven fabrics to remove the sizing substance from the warp.
The size must be totally eliminated since the fabric must absorb the liquor of subsequent
processes homogeneously.
Usually amylaceous sizes are generally used for cotton yarns, it is possible to apply amylolytic enzymes ,which carry out a biological degradation process of the starch, transforming it into soluble by-products which can be then eliminated by washing.
The enzymatic process depends on the quantity of enzyme molecules per gram of fabric, while the thermal stability of the enzyme depends on the bacteria strain from which it originates. The amylases only react with starch molecules and do not affect the other glucose polymer (cellulose), since they attack the 1.4 alpha-glucoside bond of starch and not the 1.4 betaglucoside
bond of cellulose.
This reaction take time and costly compared to other desizing agents such as alkali and oxidising agents (oxidising desizing), which attack both starch and cellulose. but with Plasma De-Sizing we do continucly and so much cheaper.
The oxidising desizing process is used to remove non-starchy sizes that do not dissolve in water or to eliminate starchy sizes combined with polyvinyl alcohol in thanks with Rotor Plasma and Ozone recovery system.
This last treatment requires accurately controlled operating conditions to solubilise only sizes and avoid any possible fibre degradation. Enzymatic desizing can be carried out in a continuous techniques are more frequent after the pad-batch wetting of the fabric. The most frequently used processes are pad-roll and pad-steam.
If the size is water-soluble, it can be eliminated by hot washing.