The purpose of the experiment is to determine the twist amount of single-ply ring yarns spun from natural and artificial, staple or filament fibers by on/off method.
(With this method, the amount of twist of the yarns produced with the Open-End rotor spinning technique cannot be determined.)
Twist; It is applied to give the fibers a permanent appearance, to increase the contact surface with each other, and to keep the fibers together.
The fibers in parallel with the twist add strength to the yarn.
A twist is given to the yarn in each turn of the twisting element.
Twist is expressed by the number of turns per unit length (such as laps/m, laps/inch, laps/cm).
The amount of twist to be given to the yarn varies depending on the type of yarn (cotton, polyester, viscose, etc.), the place where it will be used (weaving, knitting, etc.) and the spinning machine used (ring, rotor, air-jet, friction, etc.). The twist is given in the S (left) or Z (right) direction.
ISO 17202 Standard atmospheric conditions, yarn sample, tension weights, twist measuring device; It basically works according to the twist shortening (on/off) method.
Twist measuring device basically consists of two yarn clamping jaws, one movable and the other fixed.
The movable jaw can rotate in both directions and a counter is mounted on it.
The distance between the jaws can be changed depending on the sample length.
In the device, there is a mechanism that can take the elongation arising from the opening of the twist and a mechanism that can keep the yarn in a certain tension between the jaws.
Sample preparation
While the test samples are being taken, the area to be measured should not be touched in order to prevent the yarn twist from changing.
When sampling from batch production, 5 bobbins or cops are selected as samples.
The first 5 meters of the yarns in each bobbin or cop are not used as samples and are discarded due to the possibility that the twist may have changed due to the looseness of the yarn.
Test samples are taken at random intervals greater than one meter across the yarn.
Usually 10 test samples and 50 cm test length are sufficient for each yarn taken from the bobbin or bobbin.
In addition, yarn samples should be conditioned for 24 hours under standard atmospheric conditions.
The amount of tension obtained by attaching a weight (tex/2 grams) equal to half the yarn number in Tex is used as a standard.
The table of the amount of weight that should be applied according to the number for the determination of the twist is shown above.
Experimental Procedure
The twist direction of the yarn is determined.
A yarn sample of at least 10 cm in length is held in a vertical position between the thumb and forefinger of both hands.
Bend to the right with the right hand.
If the yarn twist opens and the yarn loses its strength or the fiber becomes parallel at the ends, it is a “Z” twist.
If there is an increase in the twist of the yarn, it is “S” twist.
The measuring range in the bending measuring device is adjusted according to the distance specified in the standard between the movable jaw and the rotating jaw.
The test piece is held by taking care not to deform the twisting, and it is pulled through the guides to reach the rotating jaw and the test piece is placed in the gripping jaws with a pre-stress equal to (0,5 ± 0,1) CN/tex.
Then half of the yarn count (in tex) is attached to the yarn end.
The movable jaw is brought to the "0" position.
Excess thread is cut off and discarded.
Yarn properties are entered into the twist measuring device. (yarn count, twist direction, blend number)
The twist measuring device is activated.
The movable jaw starts to rotate to open the yarn twist.
The jaw, which continues to rotate in the same direction after the twist is completely unwound, begins to give a twist to the yarn in the opposite direction of the original twist.
The device stops automatically when it reaches the starting position.
The opening and closing of the twist of the yarn can be checked with the help of a moving magnifying glass on the device.
When the test is finished, the twist value is observed on the screen on the device.
The twist value is determined according to the test method.
Sample results are noted separately.
It has an average bend.
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