Cotton yarn quality evaluation standard

Yarn quality assessment includes two aspects: intrinsic quality and appearance quality:


Basically based on physical indicators and appearance defects. However, the physical index items and appearance defect items of different types and different uses of yarn are different.


Yarn quality standards include national standards (approved by the National Science and Technology Commission), ministry standards (approved by the Ministry of Textile Industry), and enterprise standards (developed by provincial and municipal industrial departments).


The basis and classification of common yarn quality assessment are as follows:


Quality Evaluation of Cotton Yarn


Cotton yarn refers to all cotton-type yarns. Take the production of three shifts a day and night as a batch to evaluate. Its grades are divided into first-class, first-class, second-class, and third-class. Superior is equivalent to the international advanced level, and first-class is equivalent to the general international level.


Cotton yarn rated items


1. Variation coefficient of single yarn breaking strength


2.100-meter weight variation coefficient


3.Dry evenness


4, the number of cotton grains per gram


5.Total number of neps impurities in one gram


Basis for cotton thread evaluation: 1.2.4.5.


Rating method: The rating is based on the lowest one of 1 to 5, and then 1.2. Whether it is out of range, regardless of whether one or two items are exceeded, they are all downgraded to the second level for this purpose. Excellent cotton yarn plus 100,000 meters of yarn defects as the classification index.


1 single yarn (thread) breaking strength, breaking strength variation coefficient

Test 60 times on single yarn and 30 times on strand. Substituting into the coefficient of variation formula can be obtained. The formula is different for n> 50 or n <50.

Coefficient of variation

30 yarns, 1 meter per week, 100 weeks. Weigh separately at 30, and plug it into the coefficient of variation formula. Based on this, you can find the product in the technical index specification table.


3 hundred meters weight deviation

Actual and design features

The percentage deviation between the two is called weight deviation or special deviation. The actual evaluation is measured by the weight deviation of 100 meters.


4 strip evenness

Either the coefficient of variation of the evenness of the stem (measured by an electronic uniformity meter) or the uniformity of the dryness of the blackboard may be used. In case of dispute, the former shall prevail.

Determination of the uniformity of the blackboard strips: 10 cans were randomly selected, and 10 blackboards were evenly shaken, each 250mmx220mm, and they were sequentially compared with standard strip photos under the prescribed light. , Severe irregularities, etc., are assessed separately. Better than or equal to excellent is rated as excellent, better than or equal to first is rated as excellent, worse than first or with serious defects is rated as second, and severe irregularities are rated as third. Finally, the uniformity of the slivers was determined based on the ratios of superior, first, second, and third among the 10 blackboards.

51g inner neps grains and 1g inner neps impurities total grains

The number of neps grains and the number of miscellaneous plasmids in the 10 spaces of the positive and negative points. The total number of neps grains na and the total number of neps impurities in the 10 blackboards can be calculated as follows:

1g cotton nugget number = na / Ntex x10


Total number of neps impurities in 1g = (na + nb) / Ntex x10


600,000 meters of yarn defects

Yarn defects refer to major defects attached to the yarn, which are divided into short thick knots (more than 100% thicker than normal and less than 200px in length), long thick knots (more than 45% thicker than normal and more than 200px in length), and long fine knots 30 ~ 70% thinner than normal, length greater than 200px) three types. Affects the quality of the cloth surface, causing short heads. The inspection requires a large sampling volume, otherwise it is not easy to find, so it takes 100,000 meters long. Performed on the yarn flaw meter.