Method for evaluating the quality of cotton yarn

The evaluation of yarn quality includes two aspects: internal quality and external quality:

Basically, it is based on physical indicators and appearance defects. However, the physical indicators and appearance defects of different types and uses of yarns are different.

The quality standards for yarn include national standards (approved and issued by the National Science and Technology Commission), ministerial standards (approved and issued by the Ministry of Textile Industry), and enterprise standards (formulated by provincial and municipal industrial departments).

The basis and grading of common yarn quality evaluation are as follows:

Quality evaluation of cotton yarn

Cotton yarn refers to all cotton shaped yarns. Evaluate the production volume of three shifts per day and night as a batch. Its products are divided into excellent, first class, second class, and third class. Superior level is equivalent to international advanced level, and first-class level is equivalent to international average level.

Cotton yarn grading project

1. Variation coefficient of single yarn breaking strength

2. Coefficient of variation in weight per hundred meters

3. Evenness of stripes

4. Number of neps per gram

5. Total number of neps and impurities within one gram

Basis for cotton thread rating: 1.2.4.5

Rating method: Based on the lower one in 1-5, and then see if 1.2. exceeds the range. Regardless of whether one or two items exceed the range, they will be downgraded by one level and then downgraded to second level. An additional 100000 meters of yarn defects will be added as a grading indicator for premium cotton yarn.

1. Variation coefficient of single yarn (thread) breaking strength and breaking strength

Measure 60 times for single yarn and 30 times for ply yarn. By substituting the coefficient of variation formula, it can be obtained. n> The formulas for 50 or n<50 are different.

2. Coefficient of variation in weight per hundred meters

30 yarns, 1 meter per week, 100 weeks. Weigh them separately at 30 and substitute them into the coefficient of variation formula. Based on this, search for products in the technical index specification table.

3. Weight deviation per hundred meters

Actual characteristic and design characteristic

The percentage deviation between the two is called weight deviation or outlier deviation. The actual evaluation is measured by the weight deviation of one hundred meters.

4. Uniformity of stripes

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

Measurement of evenness of black board sliver: take 10 bobbins at random, shake 10 black boards evenly, each 250mmx220mm, compare them with the standard sample of black board sliver in turn under the specified light, and evaluate them respectively according to their shadows, thick knots, serious defects, serious regularity unevenness, etc. Those who are better than or equal to Excellent are rated as Excellent, those who are better than or equal to First Class are rated as First Class, those who are worse than First Class or have serious defects are rated as Second Class, and those with serious irregularities are rated as Third Class. Determine the evenness of the stripes based on the proportion of top, first, second, and third grades among 10 blackboards.

5. Number of neps within 1g and total number of neps and impurities within 1g

The number of neps and impurities within 10 spaces, the total number of neps na and total number of neps and impurities nb within 10 blackboards, can be calculated as follows:

Number of neps in 1g=na/Ntex x10

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

6. 100000 meter yarn defects

Yarn defects refer to major defects attached to the yarn, which are divided into three categories: short and coarse knots (over 100% thicker than normal, with a length less than 200px), long and coarse knots (over 45% thicker than normal, with a length greater than 200px), and long and fine knots (30~70% thinner than normal, with a length greater than 200px). Affects the quality of the fabric, causing short ends. The inspection requires a large sample size, otherwise it is difficult to detect, so a length of 100000 meters is taken. Perform on a yarn defect tester.