Preperation, Characterization And Texturing Mechanism Of Nylon/Polyester Air Textured Yran

Air textured yarn with similar bulkiness and appearance of staple yarn, as well as dimensional stability of filament yarn, is widely used in clothing, furniture, automotive interior,sporting goods and other areas, having a broad market prospect. But at present, as for multi-component nylon air textured yarn, especially nylon/ polyester air textured yarn, there is still a lack of systematic theoretical and experimental research on yarn structure, yarn apparent unevenness and filament motion characteristics.In this paper, we have chosen nylon/polyester air textured yarns as research objects and analyzed the differences of yarn physical performances as well as related changes between these yarns which produced under different overfeed rates and different components. Meanwhile, in order to study the structure of air textured yarn quantitatively, the core-and-effect structure model of air textured yarn was built based on image processing method. Three indexes including loop rate, loop index and yarn apparent unevenness, were proposed to characterize the structure and evenness of air textured yarn quantitatively. Based on the numerical simulation of airflow characteristics within the air texturing nozzle, the motion characteristics of filaments was also studied, with particle instead of filaments as research object, which was used to give more effective guidance for developing new products.In this paper, four main aspects are included:(1) Different nylon/polyester air textured yarns with different overfeed rates and different components were prepared. Air textured yarn linear density, mechanical properties, unevenness,boiling water shrinkage and yarn structure stability were studied. Results showed that: under the same overfeed rate, textured yarns with nylon as core filaments had a better ability to resist destroying, while yarns with polyester as core filaments had more stable yarn structures.According to these information, appropriate components can be chosen based on the applications of different fabrics. On the other hand, when yarns were produced with the same components,yarn density increased while yarn breaking strength, initial modulus and yarn shrinkage decreased with the increase of overfeed rate. Moreover, the yarn was also much easier to deform and recoverwhen under or release the external force.(2) Image processing method was built to analyze air textured yarn structure. Three indexes including loop rate, loop index and yarn apparent unevenness, were proposed to characterize the structure and unevenness of air textured yarn quantitatively. Results showed that: under the same overfeed rate, textured yarns with polyester as core filaments had more compact structures, and nylon textured yarn had the most significant wave distribution for its circle arcs as well as the most obvious skin-core structure. Yarn unevenness of air textured yarns with single component were higher than that of yarns composed of different components significantly. Yarn loop rate,loop index and yarn apparent unevenness were all increased with the increase of yarn overfeed rate, and the height of yarn arcs also increased.(3) Numerical simulation was applied to study airflow characteristics within three-dimensional air texturing nozzle. Air pressure contours, Mach contours, streamlines and velocity curve were recorded, in order to have a better analysis of airflow characteristics. Results showed that: after the compressed airflow entering into yarn feeding channel from the small nozzles, airflow velocity jumped up to sound speed at the junction of cylindrical pipe and trumpet shaped pipe, and even increased to supersonic as it going forward. Finally, supersonic airflow and subsonic airflow mixed at the export section. There also had a significant pressure zone in export section, forming new airflow along the face radial, which was good for filaments to move along the radial. Besides,turbulent eddies also generated within the nozzle helping filaments slip from each other, open to be more fluffy and finally entangle into circles.(4) The DMP model was applied to study the two-phase flow coupling problems in air texturing nozzle preliminarily, with particle instead of filament as disperse phase and airflow as continuous phase. Results showed that: particle moved from nozzle entrance to nozzle exit along a wavy trajectory, corresponding to the filament movements such as opening, slipping and shifting.Moreover, the path length of nylon trajectory was longer than that of ployeste under the same overfeed rate, and showed more fluctuations, inferring that the movement of nylon was more violent than that of polyester. Yarns with polyester as core yarn had obvious skin-core structure,with nylon projecting from yarn skin and wrapping around polyester. As contrast, yarns with nylon as core yarn had more loose structures, with polyester and nylon twisting with each other, which was true conformed to experimental results..