Is the spandex yarn suitable for high-speed circular knitting or air-covered yarn applications?

Breaking strength and elongation: Spandex yarn used for high-speed circular knitting or air covered yarn (ACY) must have excellent mechanical properties, especially high breaking strength and moderate elongation, which determines whether it can withstand instantaneous tension fluctuations and keep the yarn unbroken and untied during high-speed stretching, covering or weaving. High-quality spandex has an elongation of 450%–700% and a moderate breaking tension range, which can effectively adapt to the requirements of high-speed processing environments.

Thermal stability: During the air covering process, hot air is used to activate the bonding of the main yarn (such as polyester or nylon) and spandex. In this process, spandex must have good thermal stability, that is, it can still maintain its elasticity and structural stability at higher temperatures (around 170°C). If the thermal stability of spandex is insufficient, it is easy to decompose, melt or elasticity decay during the heating stage, which will affect the covering quality and product performance.

Surface smoothness: The surface finish of spandex yarn is directly related to its friction resistance during high-speed operation of the equipment. The smoother the surface, the less likely it is to generate friction heat and blockage at the yarn guide hole, tension plate, guide wheel and other locations, thereby reducing the yarn breakage rate. Especially on circular knitting machines, since the yarn passes through multiple yarn path devices continuously, any rough yarn may cause problems such as yarn accumulation and yarn skipping in the equipment.

Tension adaptability: Spandex needs to maintain uniform and stable tension during use, especially in air coating, the spandex yarn and the outer main yarn need to run synchronously with constant tension, otherwise it will cause inconsistent coating density, uneven fluctuations in the finished yarn, and even incomplete coating or exposed yarn core. High-quality spandex has strong adaptability to tension changes, which is convenient for equipment operation and product quality control.

Specification adaptability: Spandex suitable for high-speed processing is fine denier specifications, such as 20D, 30D, 40D, etc. These specifications can not only better combine with main yarns such as nylon and polyester, but also provide more stable elastic performance and yarn uniformity during high-speed spinning or weaving. Although coarse denier spandex has higher strength, it also puts a greater load on high-speed equipment and is not suitable for general high-speed circular knitting or ACY processes.

Winding process: The quality of the winding determines the uniformity and tension stability of the spandex during use. Spandex suitable for high-speed production should adopt automatic tension control winding technology, with tight winding and consistent interlayer tension to avoid yarn jumping or tension fluctuations. Especially on air covering machines, if the yarn is not discharged smoothly, it is very easy to cause problems such as yarn breakage, shutdown or abnormal covering density.

Compatibility and dyeing and finishing performance: Fabrics after high-speed circular knitting undergo post-processing processes such as dyeing and shaping. Spandex must have good heat resistance, acid and alkali resistance, and dye resistance to ensure that the elasticity does not decay and the color does not migrate during the dyeing and finishing process, and it reacts synchronously with the main fiber (such as polyester or nylon) to avoid the problem of hardening, yellowing or decreased feel of the fabric.