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Testing of polyester yarn

The tensile strength of yarn is called strength. Expressed by the load of the broken yarn, the length of the wool yarn and the yarn stretched by breaking is called elongation.

Yarn strength is closely related to fabric fastness and production efficiency. Strength is the basis of fabric strength and elongation. Therefore, the strength and elongation of wool yarn and yarn is an important index of quality. As the strength and elongation directly affect the quality, the requirements must be appropriate When the strength and elongation is too high, the wool yarn and yarn will become loose and the strength will be reduced; if the strength and elongation are too small, the strength will increase and the wool yarn and yarn will become stiff. The strength and elongation of wool yarn and yarn are different from the raw materials and processing degree, as well as the fiber arrangement. If the raw material quality is good, the fiber arrangement is neat, and the twisting is appropriate, the stronger the wool yarn is, the better the elasticity performance will be.

Strength and elongation test of single yarn

1 Overview

The performance index of single yarn drawing is one of the main basis for evaluating yarn grade. It is of great significance for yarn production, process formulation, process adjustment, weaving process and production efficiency. The evaluation indexes of yarn tensile properties mainly include average breaking strength, average elongation at break, coefficient of variation of breaking strength, coefficient of variation of breaking elongation, average breaking time, etc. in addition, in some specific situations, indexes such as breaking work, breaking strength and initial modulus are also needed. The weak link indexes such as the minimum strength and the minimum elongation in the tensile properties can be used as the reference indexes for the following process (weaving).

Principle of testing

One end of the tested sample is clamped on the upper holder of CRE type electronic single yarn strength tester, and the other end is clamped with the lower holder after the pre tension specified in the standard is applied. At the same time, the sample is stretched at a rate of 100% gauge length (relative to the original length of the sample) until the sample breaks. Due to the close combination of the gripper and the force sensor, the force sensor converts the force on the upper gripper into the corresponding voltage signal. After being amplified by the amplifier circuit, the A / D conversion is performed. Finally, the converted digital signal is sent to the computer for processing. The instrument can record the breaking strength, breaking elongation and other technical indicators of each test. After the test, the data processing system will give the statistical values of all technical indicators (see Fig. 2 for the working principle flow of the instrument). After the instrument is connected to the computer, it can also add a number of test functions, and real-time display, diagram and record the whole process of stretching, which can realize the long-term storage of data and graphics, which is more conducive to network management.

sample

The minimum number of samples to be tested is: 50 short fiber yarns and 20 other types of yarns; or the number is determined according to the product standard. The samples shall be collected uniformly from 10 packages.

On the premise that the yarn does not cause damage, a sampling plate is used to hold the sample.

Environment and correction

The test shall be carried out in the standard atmosphere required by GB 6529, and the strength measured under non-standard atmospheric conditions shall be corrected according to FZ / T 10013.1 (see Appendix). Secondary standard atmosphere was used for arbitration test.

Procedure and operation

Preheating instrument: turn on the power supply to preheat the instrument 10 minutes before the test, and the test parameters will be displayed on the display screen.

The pre tension was determined as (0.5 ± 0.10) CN / tex and (0.25 ± 0.05) CN / tex respectively. The pre tension requirement of textured yarn can eliminate the yarn curl without elongation. If there is no other agreement, the following pre tension is recommended for textured yarn (except carpet yarn with linear density over 50 Tex).

In the textile industry, polyester yarn should always be tested in laboratory, so as to know whether the production is normal or not.