1, the physical characteristics of short fibers

Different short fiber spinning technologies have different effects on the physical properties and appearance of yarns, and even affect the characteristics of the final product.

(1) Different spinning methods for yarn structure, the structure of short fiber yarn is different from that of filament yarn, the first is the arrangement of the external and internal fibers of the yarn, and the external structure includes the appearance and surface structure of the yarn. Such as: the arrangement of fibers on the surface of the yarn; The hair of the yarn; Friction coefficient of yarn; Characteristics of yarn; Wear resistance and other surface properties of yarn.

(2) The internal structure of the yarn is mainly the fiber in the entire cross section of the yarn body and the longitudinal arrangement of the yarn. The internal structure of the fiber orientation, elongation, displacement and twist includes: the strength of the yarn; Fiber mixing degree; Bending strength; Compressibility; Resilience (with a tendency to knot).

The above explanation of the meaning of the structure is not necessarily complete, but it provides the complexity of yarn characteristics.

2. Spinning process

In order to get an idea of the effect of spinning process on yarn structure, 3dtex and 38 mm viscose staple fiber were used for test spinning in 5 different spinning process systems.

A\ traditional ring spinning process; B\ compact ring spinning process; C\ double nozzle (MTS) false wrapping spinning process; D\ vortex spinning (MVS) spinning; E\ spinning cup.

(1) As mentioned above, the external structure of the yarn can be seen on the scanning electron microscope camera. Application of microelectronic photography Photograph: There are five kinds of spinning, jet spinning, vortex spinning, ordinary ring spinning and tight ring spinning. From the photos, it can be seen that the external fiber orientation of the yarn produced by the five kinds of processes is more fiber forming yarn in the external structure of the tight ring spinning yarn, and almost all fibers are formed in the yarn body, which improves the short fiber yarn, and the twist structure of the yarn is clearly seen. In addition, one end of the fiber is twisted into the yarn body along the length of the yarn, and the tight-ring spindle yarn has the best orientation.

(2) Traditional ring spinning, under the same twist conditions, the surface of traditional ring spinning is disordered, a large number of fiber ends are not twisted into the yarn body, and a single fiber extends outside the yarn, which may be caused by steel collar/wire ring or yarn guide.

(3) Vortex spinning, similar to ring spinning, the fibers are arranged well in the yarn body, the spinning speed is 350/ time, and the wrapped fibers are fine. The twist is basically the same as the ring spun yarn, and the actual twist of the yarn is basically the same as the calculated twist. The ratio of wrapped fiber to untwisted core fiber is very high, and almost all cover the core fiber. Therefore, the appearance of vortex yarn is basically similar to that of ring spindle yarn, and the outer wrapped fiber and untwisted core form true twist together.

(4) Double jet spout false twist yarn, double jet spout false twist yarn, and vortex yarn its essence is different, double jet spout jet yarn wrapping fiber only accounts for 6%-8% of the total fiber about 90% of the fiber is stretched without twist, you can clearly see that the wrapping fiber on the yarn core wrapping tighter than vortex yarn.

(5) Spinning cup spinning, regardless of whether the spinning cup yarn belongs to the true twist category, but the fiber arrangement on the spinning cup yarn is disordered, the middle fiber of the yarn shows no clear spiral in the Z direction and S direction, and the fiber is straight. It can be clearly seen that the wrapped yarn has no entanglement, which is the advantage of the spinning cup yarn and the basis of the characteristics of the spinning cup yarn.

The flaring and hairiness caused by spinning is a very troublesome problem. Hairiness has many negative effects in the downstream processing process, and the textile feel and final product properties are affected by hairiness. zweigle hairiness test is applied to classify hairiness of 1mm-2mm and separate harmful hairiness of more than 3mm. If the ring spun yarn hairiness is 100%, the tight ring spun yarn, vortex spun yarn and rotating yarn 1 mm to 2mm hairiness is less than the ring spun yarn hairiness, the double nozzle false twist wrapped yarn, the wrapping situation is poor, more hairiness, the application of SO Called detector can measure the yarn caused by friction during the post-processing, the friction is measured by rubber ring. Tight yarns have better friction resistance than traditional yarns. The hair protruding from the spinning cup yarn is less, especially the viscose fiber is more obvious, and the fiber on the yarn will not break, but many of the hair is wrapped in the fiber on the yarn body, so the spinning cup yarn is less hair.

4, the volume of yarn

Yarn volume is an important index to reflect yarn covering ability. When tightly spun ring spun yarn and ordinary ring spun yarn have the same twist, the latter's final product covering ability is lower. Under the condition of maintaining the same strength, the twist can be appropriately reduced to increase the yarn volume, and the covering capacity of ordinary ring spun yarn can be obtained, and the twist can be reduced by 5% ~ 10%. Denkenolorf yarn structure tester provides a measured yarn volume with a yarn length of 0.3mm. The detection of yarn volume includes the same yarn count double nozzle MJS jet yarn, because the jet yarn is wrapped yarn, false twist, so the same yarn count is larger than the ring spindle yarn volume, the graphics captured by microelectronic scanning photography technology show that a small amount of wrapped fiber on the yarn core, and the length is very short so that many parts of the yarn fiber is basically twistless.

The friction resistance and stress load of the warp yarn are the application of So-Called analog index, which can be tested at the same time for the required 15 yarns. The fiber arrangement of the ideal compact ring spun yarn is shown to be superior to that of ordinary ring spun yarn. Traditional spinning technology has shortcomings, this new spinning in the warp must be processed, in the jet spinning technology, relative to the true twist yarn, the yarn on the fiber is very little, there is a straight winding situation, therefore, the mechanical and physical properties of the yarn, especially in the winding (winding) more obvious, or the difference between traditional spinning and ring spun yarn.

5. Internal structure of yarn

The formation of the fiber inside the yarn is related to the external structure of the yarn, the arrangement of the yarn core inside the yarn, and the extension of the fiber along the direction of the yarn length can be obtained during the drafting process through electronic scanning photography, and the fiber height is parallel from the cross section of the yarn, and affects the yarn strength. The yarn strength characteristics are related to the clamping length during the test.

Reduction of detail and possibility of strong and weak loops: Normal yarn strength is tested on a clamping machine with a clamping length of 520 mm, and there are also clamping lengths of 100 mm and 18mm. The clamping length is reduced, and the breaking strength of the yarn is increased, which is due to the short clamping length, the probability of weak strong rings and details is reduced, the breaking length is reduced, and the breaking opportunity is less. If the fiber distribution orientation is good, the test clamping length is reduced, the breaking strength of yarn is increased significantly, and the ring spun yarn and tight ring spun yarn are more obvious. The breaking strength of the spinning yarn is low, even if the breaking length is lower than the fiber length, because the fiber forms a curved hook, even if the breaking length is short, the breaking strength of the spinning yarn will not be increased. In short, the more the number of yarn fibers is clamped, the better the longitudinal orientation of fiber and the increase of yarn breaking strength. It can be seen from the electronic photographic scan that the spinning cup yarn is a winding structure. Even if the clamping length is less than 5mm, 100% of the fiber will be gripped and the fiber will be broken. The clamping length is 0 mm, the fiber breaking length is lower than the fiber length, and the poor orientation of the yarn core fiber will cause low breaking strength.

The strength of jet yarn is between ring spun yarn, tight yarn and spinning yarn, mainly jet yarn, yarn core is parallel to spinning yarn, less wrapped fiber, strength is less than spinning yarn.

6. The formation of yarn affects the characteristics of yarn deformation

For example, yarn bending strength is a characteristic that is affected in the process of yarn formation, but it is difficult to detect yarn bending strength. A new method for testing the bending strength of yarns has been developed. The experimental results show that if the bending strength of tight yarn is 100%, then the bending strength of spinning cup spinning and vortex spinning is 200%, and that of double jet jet spinning is 300%. These numerical relationships can be compared with that of ring spun yarn on woven fabrics and knitted fabrics. There is also a small difference in bending strength between ordinary ring spun yarn and tight spun yarn.

Another problem arises, when the yarn deforms, when the yarn is compressed on the cross section of the warp and weft yarn. The measurement of coarse knots of yarn shows that the coarse knots decrease when the compression force of yarn increases.

The spinning cup yarn structure causes the distribution of fibers. In the wrapping of fibers, the feel is harder, and the deformation force is smaller than that of the yarn without wrapping. The knitted fabrics and woven fabrics produced by rotating cup yarns often have a rougher appearance than ring spun yarns.

For comparison, the coarse knots of the yarn were tested under 1OOcN pressure, which showed that the yarn had the best twist structure. The MTS double jet jet yarn with the same deformation had about 95% parallel fibers without twist, which was more prone to deformation. According to this test, the spinning yarn felt relatively hard, and the yarn deformation could be detected by the tightness of the yarn on the loom or knitted fabric appearance.

7, the resilience of yarn

The resilience of yarns is very important for textile processing, such as skew distortion of knitted fabrics. Resilience is measured by detecting the knot force of yarn. The resilience of true twist yarn such as tight ring spun yarn and ordinary ring spun yarn is different from that of traditional yarn. The knot of spinning cup yarn is lower in normal twist or reverse twist.

The lower resilience of air-spun yarn is mainly due to the higher proportion of parallel untwisted fibers, and the greater resilience of true twisted yarn than that of traditional yarn, so the fabric skew is less when further processed into knitted fabric.

8. Conclusion

Yarn structure is one of the important characteristics of yarn, yarn appearance is related to yarn properties, yarn internal fiber arrangement has a great influence on yarn properties, especially on the further processing of yarn and the final product properties. Poor yarn structure has a great impact on the post-process processing, the application of good yarn structure has a particularly good function, the use is also very good, in the adaptability of tightly spun yarn textiles, the appearance of the structure is the most ideal.