Strength is the resistance of the yarn against the applied load. The high strength in the yarn reduces yarn breaks and machine downtimes, thereby increasing productivity. The purpose of the strength control is to determine the yarn breaking strength and breaking elongation. As the name suggests, it is to measure the durability of the product according to certain conditions. This test is done only on yarn.
The most important factors affecting yarn strength
1-Type of raw material,
2- Fiber length,
3-Fiber length distribution,
4-Fiber strength,
5-Twist in yarn,
6-The parallelism of the fiber,
7-Irregularity rate,
8-Moisture and foreign matter ratio
Raw material type
The strength of linen, cotton, nylon, rayon, and wool decreases from left to right, while the percentage of elongation increases.
Fiber length distribution
If the variability in distribution is high, this will cause a change in strength. Among the yarns with the same staple length but different short fiber ratio, the strength of the yarn with more short fiber ratio will be lower.
fiber length
If the fiber length increases, the strength of the yarn will also increase. This is because the fibers will hold together better. The strength of the yarn produced from short fibers is low.
fiber strength
If the strength of the fibers increases, the strength of the yarn also increases.
Parallelism of the fiber
The fact that the fibers are parallel to each other ensures easy opening. Thus, the strength of the yarn decreases.
twist
It increases the strength of the yarn up to a certain limit. However, if the critical point is exceeded, the strength of the yarn decreases.
Unevenness rate
As the unevenness of the yarn increases, the strength of the yarn decreases.
Moisture and foreign matter ratio
Depending on the type of fiber, the amount of moisture causes the strength to increase or decrease. Foreign substances reduce the strength.
Yarn strength and elongation are among the most important quality values of yarn. Because the yarn is exposed to many tensions until it becomes a fabric. In order for a textile surface or product to be produced, the yarn must be able to withstand these tensions during the production phase. In addition, after the textile surface or yarn is ready to be presented to the user, the textile product must be resistant to the loads and strains it will be exposed to during use. There is a required minimum yarn strength value for each usage area. While producing the yarn, it should be produced in such a way that this strength value is provided. For this reason, it is very important to control the strength values during the production stages while they are still semi-finished and to determine whether they provide the required values.
Dynamometer (Strength Tester)
The strength test device is used to measure the strength of the yarn.
The sample yarns are rested for at least 3 hours under standard atmospheric conditions before the test, and it is ensured that they reach a constant moisture balance. If the weight loss is less than 2% in the weighing of the yarn left at standard atmospheric conditions at 0,25 hour intervals, it is considered that the sample has reached the test conditions. It is recommended to make at least 5 measurements from each bobbin or bobbin set as a test sample. The number of sample bobbins or bobbins to be taken should be statistically selected depending on the amount of mass (lot) about which information is desired. In large batches, increasing the number of samples will be correct to get a more reliable idea of the whole lot. The samples should be conditioned for 20 hours under standard atmospheric conditions (2 ± 65 °C temperature and 2 ± 24 % relative humidity) before the test. The test should be carried out under standard atmospheric conditions.
Conducting the strength test
1- 10 bobbins taken from the spinning machine according to the spindle number, respectively cIt is attached to the hanger part of the device.
2-Up to 40 coils can be attached to the device hanger and can be tested one after the other.
3-The threads to be tested are passed through the guide on the device, respectively, and tied.
4-The amount of yarn that should be in the cop for the test should be 8,5-11,5 g. 5 tests are made from each yarn and each test is completed in 20 seconds.
5- In the computer part of the device, data about the test are entered.
o Yarn number (16/1),
o Twisting of the yarn,
o How many rounds will be drawn (5 rounds),
o How many coils (number of coils on hanger)
o Machine number
o Time setting is checked, 20 sec± 3 time settings are made.
o The force applied in the device varies according to the yarn number. For example, the applied force for Ne 16/1 yarn is 18.8 gf.
The test is started with 6-Start/stop.
7-The thread holding mechanism (jaw) holds the thread and compresses it between the lower and upper jaws.
(The jaw spacing is 500 mm for straight and twisted yarns.)
8-A certain force is applied to the lower jaw.
(With the effect of this force, some elongation is seen in the thread and the thread breaks depending on the durability of the thread.)
Elongation Percent Reading
The force when the thread breaks, "Breaking Force" is defined as. The ratio of the amount of elongation until the yarn breaks to the first length of the yarn. “Elongation at break” is named and % It is expressed as.
>> Strength of the thread at break with the pulling of the thread by the lower jaw; The test is automatically performed according to the program, the result is taken from the printer, the values are saved on the test form.
>> The force/elongation diagram obtained during the test can be viewed on the computer screen and can be printed on the printer together with the test data (tenacity, elongation, test no, breaking time, breaking load values).
