What is false twist deformation of drawn yarn

The polyester drawing yarn is straight, smooth, closely arranged with each other, and has poor fluffy property. It can only be used in silk-like fabrics, which limits its application. For this reason, a variety of modification methods are adopted to increase its new properties, so as to expand its application scope.

 

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False twist deformation is one of the most important physical modification methods. Polyester false twist textured yarn came out in 1955. It has high elastic yarn, medium elastic yarn and low elastic yarn. Among them, low elasticity yarn not only has certain elasticity and fluffiness, but also has the geometric dimension stability required for making coats, so it is widely used.

 

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polyester filament is basically produced by false twist deformation. There are two kinds of false twist deformation methods: rotor type and friction type. Rotor false twist deformation was developed earlier and the product quality was better, but the production efficiency was not as high as that of friction type. At present, most of the false twist texturing machines for drawing yarn are rotor-type, and the rotor-type false twist texturing machine is also used to stretch POY yarn.

 

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The Principle of False Twist Deformation

 

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1. False twist

 

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If one end of the filament is fixed and the other end is held to rotate itself, each turn adds a twist to the filament, and S twist is obtained by turning counter-clockwise and Z twist is obtained by turning clockwise. If both ends of the yarn are fixed, the middle part of the yarn is held and rotated. With the holding point as the boundary, the upper and lower parts will be twisted with the same twist number and opposite twist direction respectively.

 

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If the silk moves through the fixed points at both ends and rotates the grip points, the twisting will change. Before the grip point, the silk is twisted (assuming Z twist); after the grip point, the S twist equal to the number of Z twists is added. Because the twist direction of the grip point is opposite to that of the bottom, the Z twist added before the grip point is actually unrolled. This process of first twisting and then untwisting is called false twisting.

 

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In the false twist texturing machine, the small rotor is a rotating gripper. The feeding roll and the intermediate roll not only fix the ends of the yarn, but also continuously transport the yarn forward. The filament is twisted before entering the small rotor and untwisted after leaving the small rotor. The filament is untwisted.

 

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2. Heating and cooling

 

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heating and cooling are necessary conditions for obtaining false twist effect by using thermoplasticity of synthetic fibers. The purpose of heating in the twisting stage of false twisting is to eliminate the internal stress caused by twisting and fix the twisting deformation by the thermal motion of molecules. In addition, after heating, the plasticity of the filament increases and the rigidity decreases, which can reduce the twisting tension and facilitate twisting.

 

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The purpose of_cooling is to fix the plastic deformation resulting from twisting deformation. If the wire in the thermoplastic state passes through the rotating gripper (small rotor) immediately, untwisting will not work and produce rigid wire with very poor fluffy property. When it is cooled below the secondary transition temperature (glass transition temperature, 81 C), the twisted deformation has solidified. Although untwisted, each single filament still retains its original curl shape, which is fluffy and elastic.

 

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In summary, the false twist deformation is based on the thermoplasticity of the yarn. After twisting, the yarn is heated and shaped, then cooled, and after cooling, all the twists are untied. As the twisted yarn is heated and cooled, the bending shape of the yarn is fixed, and the yarn remains bending after untwisting.

 

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The

 

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The balanced drawing silk tube is mounted on the precursor trolley or bench. The two tubes are in a group, head and tail are connected, and one is equipped.

 

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drawing wire is first put into the cutter after adjusting the tapping tension. When there is a broken end, the controller drops the needle, turns on the circuit, cuts the wire, and prevents the winding roll from occurring. There is a false twist deformation zone between feeding roll and intermediate roll. The filament is twisted and heated in the first hot box (deformation hot box). After passing through the cooling zone, the filament is untwisted through the center hole of the small rotor and the cross pin of the false twisting device.

 

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After leaving the intermediate roll, the_wire enters the setting area. After untwisting, the yarn passes through the second heat box (stereotyped heat box) to complete the stereotyping. Between the tapping roll and the auxiliary roll, there is a stable and winding tension regulating area in which the wire passes through the broken wire detector. After false twisting, the deformed yarn is sent out from the auxiliary roll, and coiled on the barrel tube through the oil roller to the barrel rack.

 

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In the whole process of deformation, the silk path is longer. In order to facilitate operation, reduce equipment height and occupied area, the method of circuitous progress according to process is adopted in production.

 

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3. Technological conditions of false twist deformation

 

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The main technological conditions of_false twist deformation can be summarized as four, namely twist.

 

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Twist, Tension, Temperature and Time are often called four "T" because their first letters in English are T.

 

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In setting the process conditions, we should consider not only the quality of false twisted textured yarn, but also the processability. The first order of setting is twist and the first overfeeding/underfeeding rate (broken ends, dyeing rate, strength, etc.).

 

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After the twist is determined, the speed and speed of the small rotor can be determined according to the performance and operation level of the false twister. Then the second overfeeding/underfeeding rate and the temperature of the first and second heaters are determined according to the crimp characteristics and dyeing performance requirements of the products. ^ After that, the over-feeding rate and other forming conditions of winding are determined in order to obtain a well-formed cylinder.