1. Single yarn breaking strength and single yarn streng […]
1. Single yarn breaking strength and single yarn strength variation coefficient
The standard of "Cotton Natural Yarn" regards the yarn breaking strength as a secondary indicator, and only the first gear level is used as a drop. However, the practice of dyed yarn has proved that the breaking strength of the yarn has a great influence on the post-processing. The breaking strength is too low, and the weaving ends increase, which not only reduces the weaving efficiency and increases the defects. Therefore, the single yarn break strength is used as a graded assessment index in the color spinning yarn standard, which has tightened the requirements, and according to the characteristics of the color spinning yarn, two indexes, the ratio of colored cotton greater than 50% and less than 50%, are formulated accordingly.
The single-yarn strength variation coefficient is a discrete index reflecting the difference of single-yarn strength. The smaller the dispersion, the more uniform the single-yarn strength. In the weaving process, there are few interruptions, good weavability, and correspondingly improved product quality, so users have higher requirements on the single yarn strength variation coefficient than the single yarn breaking strength. In the formulation of dyed yarn standards, premium products are required to reach 25% of the Uster statistics in 2007.
2. Yarn evenness
The inspection method of the evenness of the yarn in the standard of natural color yarn is carried out by instrument or visual inspection, and is arbitrarily selected by the enterprise. Due to the particularity of the color-spun yarn, the visual inspection of the uniformity of the bar is difficult to operate. Therefore, the method of visually inspecting the bar drying is eliminated in the standard, and the electronic bar uniformity tester is used for inspection. However, the index level is lower than that of natural yarn. Taking 18.5tex pure cotton yarn as an example, the superior quality of natural yarn is 15.5%, and the color spinning is 16.5%.
3. Variation coefficient of 100-meter weight
The 100-meter weight variation coefficient reflects an important indicator of the uniformity of long yarn segments. Due to the low value of the index in the standard of natural yarn, the standard of colored yarn has been greatly improved. For example, the quality of pure cotton yarn is 1.8%, which is close to 25% of the statistical value of the 2007 Uster Gazette. This data mainly considers that many enterprises are equipped with self-leveling devices in the final draw frame. Generally, enterprises equipped with self-leveling devices on the final draw frame can fully reach the 25% level of the 2007 Uster Gazette statistics. Well-managed enterprises can reach the level of 5-10% of the statistical value.