Ivana Schwarz

The Effect of Microwave Drying on Warp Sizing

The paper describes our research of microwave usage in drying the size pick-up. An analysis of three different drying processes in relation to physical-mechanical properties of sized yarn has been carried out. Under the same sizing conditions, but different drying methods, the following parameters were determined: breaking force, elongation at break, abrasion resistance and yarn hairiness. The application of microwave drying method for warp sizing showed to be equally good, or even better in some cases, compared to the conduct and convection drying methods.

Analysis of changes in mechanical and deformation properties of yarn by sizing

The purpose of this paper is to show the degree of changes in mechanical and deformation properties of single cotton yarn after sizing depending on their fineness, size concentration and the structure created by the type of yarn spinning. The properties of ring and rotor-spun yarns were analyzed before and after sizing with a PVA sizing agent, using the same recipe, but with two different size concentrations — 7.5% and 5.0%. Standardized methods for determining the mechanical properties were used, as well as a modified method for cyclic testing to determine areas of elastic, viscoelastic and plastic yarn deformations. There are no significant differences in yarn properties after sizing with lower and higher size concentrations, which leads to the conclusion that it is a greater advantage to use a lower concentration, in order to achieve better economic and environmental effects. By sizing, a ring-spun yarn achieves major improvements, particularly in more refined yarns (20, 30 tex), which is positive because improvements in mechanical properties of these yarns are more necessary. Contrary to this, with a rotor-spun yarn the improvements are relatively low, due to its structure. Cyclic loading of yarn showed a difference in changes of deformation areas of unsized and sized yarns, primarily in the way of reducing the elastic area of deformation, depending on yarn structure. Information obtained by this analysis can improve the quality of sizing with possible cost savings and contribute to a better regulation of weaving conditions and thus to an increase in the quality and performance of weaving.

Analysis of Size Pick-up and Mechanical and Surface Properties of Multicolored Warps

The impact of various colors in a multi-colored warp on size pick-up was tested. Likewise, the change of physical-mechanical properties of yarn by sizing multi-colored warps was examined. Tests were performed on various multicolored warps for each color. Based on the obtained results, we concluded whether there was a difference in the size pick-up among various colors of the warp, as well as a difference in physical-mechanical yarn properties under the same sizing and dyeing conditions.

Weaving Complex Patterns — From Weaving Looms to Weaving Machines

A chronological overview of the historical facts of the art of hand weaving, with an emphasis on the development of large and complex patterns is provided. The development of looms or weaving machines through history for weaving fabric with large patterns is described. Hand weaving complex patterns from primitive weaving on frames to more complex weaving with two weavers operating one loom was especially explored. The beginning of Jacquard weaving and its application even to the electronic Jacquard looms has been emphasized. An analysis of the development of patterned fabrics with multiple effects was carried out. The nalysis was conducted according to patterns using the shortened version of drawing a sample. The results show that it is possible to determine the echnique of weaving and construction parameters of each fabric pattern that vary in color and/or in a weave used. The most accurate way to ighlight the contours of the points of the transition of one effect into another, namely by shifting warp and weft interlacing points on the edges of each pattern (opposing thread float), is described. Based on the obtained results and finding an identical yarn, it is possible to replicate the pattern on the Jacquard loom.

Physical–mechanical properties of automotive textile materials

The role of automotive textile materials is of great importance and therefore this paper analyses the properties of such materials – airbag fabrics and upholstery fabrics. Fundamental characteristics and construction parameters of airbag fabrics and artificial leather with bonded textile fabric on the back side, as well as joining (sewing) and quality of joining places of cut parts are crucial for durability, comfort and aesthetics of the automotive interior design, and therefore were analysed. Airbag fabric specificity and extreme values of several parameters are achieved by manufacturing process, with extremely high densities in the warp and weft direction, resulting in a great strength and air permeability properties of very low level. The most important parameters for upholstery fabrics (artificial leather) durability are breaking force and elongation at break, and they were tested in different circular directions. Tests showed the direction with greater breaking properties, what is of paramount importance.

Analysis of woven fabric at the place of the sewn seam

Abstract Key importance and the role of sewn seam in the woven fabric are presented. Fabric properties in the places joined with the sewn seam on which garment durability, applicability, appearance and quality depend are highlighted. Seam location is usually the weakest spot on the garment, especially when the great loads are present at these places. Mechanical properties of the sewn fabrics were investigated in different test conditions. The influence of the load on the sewn seam is analyzed in time intervals. Sample with seam have approximately 70% lower breaking properties (breaking force and elongation at break) than the sample without seam. By preloading the seam fabrics with 30%, 50% and 70% of elongation at break, for a 3-h period, the effect on mechanical properties were tested and the differences in pre-stretching intensity were observed. By conducting such test, it is expected that the fabric experience further degradation and that breaking properties further reduce, but the exact opposite occurred (breaking properties, by increasing the preload, increase even more), because of various material properties (structural fabric properties, raw material characteristics, seam characteristics).

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). Todays 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 todays 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).