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High quality 40s/2 polyester sewing thread

Yarn result and calculation

1. Breaking strength

Where: - average value of breaking strength, CN;

- breaking strength value of each time, CN;

- number of stretches.

Note: 1. If not under the standard temperature and humidity conditions, the measured results are different.

2. Breaking strength refers to the ratio of yarn breaking strength to its linear density, usually expressed in cN / tex.

⒑ 2 elongation at break:

Where: - average elongation at break,%;

- elongation at break,%;

- number of stretches.

——Standard deviation;

——Each time measured data value;

——Average value of test data;

——The number of test pieces shall be at least 50;

——Coefficient of variation,%.

3. Test report

Record: instrument test parameters, including test date, instrument model, sample name, specification, temperature, humidity, etc.

Results: breaking strength, breaking strength, elongation at break, coefficient of variation of breaking strength and elongation at break, etc.

Test related knowledge

Comparison of different tensile testing mechanisms

1. Standards and instruments: GB / T 3916 method standard is equivalent to ISO 2062 standard, which is applicable to various product standards covered by it. CRE (constant speed elongation) strength tester is specified in the standard, while CRL (equal load) and CRT (constant speed traction) instruments specified in the old standard are only used as transition, and can be used according to the agreement. GB / T 3916 standard adopts constant speed drawing instead of the old standard. For example, when CRT instruments were widely used in the past, there were inevitable negative errors of mechanical friction and self-stop mechanism. In addition, uncertainty error caused by inertia of force measuring mechanism and human error of operators can not be ignored.

2. Advantages of CRE single yarn strength tester: most of CRE (constant speed elongation) strength tester adopts non electric measurement technology, and the mechanical friction and inertia influence of force measuring sensor are almost negligible, and the operator's human error factors are less, so the measured results are more accurate. In addition, the electrical measurement system can be connected with the computer, so the work efficiency is high, especially the powerful data analysis and storage function, which is completely incomparable to CRT mechanical strength tester.

Three The influence of tensile speed on breaking strength: when the yarn sample is stretched at a relatively low speed, the increase rate of the cohesion force between the fibers is relatively small, and some fibers in the sample break in the form of extraction; when the yarn sample is stretched at a relatively high speed, the cohesion force between the fibers increases rapidly, and the ratio of fiber fracture in the sample increases under the action of force The breaking strength of the sample increases. In addition, the force required for the extraction and breaking of fibers in the process of yarn drawing is also related to the twist factor of the sample.

3. CRE single yarn strength tester can be divided into semi-automatic and full-automatic: the semi-automatic instrument abandons the complicated automatic tube changing and yarn guiding auxiliary system, simplifies the instrument structure and control circuit, reduces the cost and increases the reliability. In the working process of the instrument, tube changing, yarn drawing and other processes can be carried out at the same time through the way of human and machine crossing, so as to improve the working efficiency of the instrument; its disadvantage is that the labor intensity of the operator is large. Although the labor intensity of the operator is small, the reliability of the automatic instrument is slightly worse than that of the semi-automatic instrument, and the price is relatively expensive.

4. The basic requirements of different test materials for the instrument: firstly, the instrument should meet the strength requirements of the sample fracture. The test interval length should be reduced for the sample with larger elongation. For the sample with small elongation, the force measuring system of the instrument should have enough sampling rate. For the instrument whose sampling rate can not meet the requirements, sometimes it can be compensated by reducing the tensile speed.

Five The requirements of different test materials for the instrument holder: the yarn spun by staple fiber has no special requirements for the holder; the holder for the sample of chemical fiber filament should use a soft cushion with appropriate hardness and be pressed continuously during the stretching process to clamp it; the sample with high breaking strength should be held in the groove led out by the holder. In a word, it is necessary to ensure that the sample does not slip off and does not break at the edge of the jaw.

6. Some manufacturers developed portable electronic single yarn strength tester in 2013, which can be used to test the joint strength of Air Twister on site. With the continuous emergence of new materials, the requirements of testing technology are higher and higher. With the intervention of computer technology, the accuracy of the instrument is higher and higher, and the function is more and more powerful. Most of the functions that we hope to get are easier to realize.

After testing, we can intuitively show where the quality of yarn goes, so in the production process of polyester yarn, testing is very important.