Sizing agents for filaments are soluble polymers building up a film on the surface of the fibre and protecting the yarn against any effect of abrasion and mechanical tension that may occur during weaving. Size must be easily applicable, extremely protective during weaving and easily removable or washable during the desizing process.
Moreover, sizes must be easily biodegradable and should not excessively affect the polluting load of the water-treatment plant.
Nowadays, ever-increasing weaving speeds and the greater complexity of fabrics pose more and more interesting challenges on sizing.
Sizing increases tenacity and resistance to abrasion of warp yarns by building up a protection film that can resist any kind of stress during weaving (cyclic tensions, flexures, abrasion against various parts of the loom and yarn-to-yarn frictions).
The efficacy of the sizing product depends not only upon adhesion between size and yarn, but also upon the capacity to build up a resistant and elastic film.