3 A New Pre - Wet Sizing Process – Yes or No ?

As one of the most complex steps in fabric production, sizing plays a very important role in the weaving process. The primary purpose of the sizing process is to obtain the warp threads that can successfully be woven without major damages which occur during the yarn passage through sliding metal parts of the weaving machine (Lord, 2003). It applies to the improvement of physical and mechanical parameters of warp threads, primarily to increase strength and abrasion resistance and thus to reduce the number of warp breaks to a minimum in order to achieve the maximum efficiency of weaving machines and energy savings. Also, the goal of sizing is to keep the fibers in the yarn in a position where they were before sizing, with minimal yarn deformations during weaving. The success of the weaving process depends on the complexity of several factors including the characteristics of the desired material, the sizing process, the sizing ingredients and yarn properties, but also the extensive knowledge of a textile technologist (chemistry, rheology, electronics, mechanical engineering, physics, mechanics, mathematics, etc...), which makes this process more difficult and more important for the overall process of making woven fabric (Adanur, 2001). Today's achievements in all engineering branches enable an exceptional progress of the sizing processes to achieve a very high quality of sizing that meets the needs of today's modern weaving. However, the sizing costs, despite the complete automation of the regulation and control of the most important sizing process parameters, are still very high. Their reduction is possible by reducing the consumption of sizing agents and energy, as well as by modernization and development of machinery and technology, and all without consequence on the quality of the sized yarn. The choice of sizing agents plays the most important role in meeting all the requirements placed on the sizing process and sized yarn as well as optimizing and keeping the sizing process conditions and the size pick-up constant (Kovačević et al., 2006). Even today the optimization of the size pick-up applied to the yarn presents a major problem in the sizing process, despite the high degree of automation and high quality sizing agents. Influential parameters in the optimization of size pick-up are defined with the substance balance that enters and exits the size box (Equation 1). The requirement of keeping the size pick-up optimized and constant can be achieved by continuous measuring and keeping temperature and yarn moisture, size concentration in the size box constant, as well as automatic regulation of squeezing force and sizing speed (Pleva & Rieger, 1992; Soliman, 1995).