What are the key points of quality control for Polyester DTY?- Hengke Textile Technology Co., Ltd

The key points of quality control for Polyester DTY (polyester stretched textured yarn) mainly include the following aspects:
Raw material quality control
Polyester chip quality: The intrinsic viscosity of polyester chips should be stable, generally between 0.64-0.68dL/g. The intrinsic viscosity reflects the molecular weight of the chips, which directly affects the spinnability and strength of the finished yarn. At the same time, the end carboxyl content of the chips should be controlled, usually less than 30mol/t. Too high end carboxyl content will lead to decreased thermal stability of the fiber and poor dyeing performance.
Additive quality: The quality of additives such as matting agents and antistatic agents added in production is also crucial. Taking matting agent titanium dioxide as an example, its particle size distribution should be uniform, generally controlled at 0.2-0.3 microns. If the particle size is too large, it will cause defects on the fiber surface, affecting the appearance quality.

Spinning process control
Temperature control: The temperature of the spinning box is generally controlled at 280-290℃. Too high temperature will degrade the polyester melt, resulting in a decrease in molecular weight and fiber strength; too low temperature will cause poor melt fluidity, and hair and broken ends are prone to occur.
Spinning speed: The appropriate spinning speed helps to ensure the quality of the fiber, usually between 3000-6000m/min. If the spinning speed is too fast, the internal stress of the fiber is large, which can easily cause uneven fiber structure and affect the post-processing performance; if the speed is too slow, the production efficiency is low, and the fiber orientation is not enough and the strength is insufficient.
Component filtration: The filter screen in the spinning component should have appropriate accuracy. Generally, a multi-layer filter screen combination, such as 200 mesh, 300 mesh, 400 mesh, etc., is used to effectively filter impurities and gel particles in the melt to prevent them from entering the fiber, causing spinning broken ends or defects on the fiber surface.

Stretch deformation control
Stretch multiple: Stretch multiple is one of the key factors affecting fiber performance, generally between 3.5-5.0 times. If the stretch multiple is too large, the fiber is easy to break and the feel becomes hard; if the stretch multiple is too small, the fiber strength and orientation are insufficient, and the elasticity and fluffiness are not ideal.
Hot box temperature: The hot box temperature during the stretch deformation process is generally set at 180-220℃. If the hot box temperature is too high, the fiber is easy to turn yellow and brittle, affecting the color and feel; if the temperature is too low, the fiber shaping effect is poor, and the curl and elasticity are unstable.
False twist tension: The false twist tension should be properly controlled, generally between 2-5cN/dtex. If the tension is too large, the fiber curl is small, the feel is hard, and it is easy to have hair; if the tension is too small, the fiber curl is unstable, and it is easy to have problems such as hooking and fluffing after yarn formation.

Finished product inspection control
Physical index inspection: including fiber linear density, strength, elongation, curl shrinkage, etc. The linear density deviation should be controlled within ±1.5%, and the strength variation coefficient should be less than 5% to ensure the uniformity of fiber thickness and strength stability.
Appearance quality inspection: mainly check whether the fiber has defects such as hair, broken ends, oily and dirty fibers, and stiff fibers. Hair will affect the smooth progress of subsequent processing, oily and dirty fibers will cause uneven dyeing, and stiff fibers will reduce the spinnability of fibers and the quality of fabrics.
Dyeing performance inspection: Through simulated dyeing tests, the fiber's coloring rate, color fastness and other indicators are tested. The coloring rate should be stable, and the color difference with the standard sample is generally required to be controlled at more than 4 levels, and the color fastness should reach 3-4 levels to ensure the color brightness and durability of the fiber after dyeing.