There are differences in the effects of different staple fibre spinning processes on the yarn’s physical properties and appearance, and even on the characteristics of the final product.
Different spinning methods on yarn structure, the structure of staple fibre yarn is different from that of filament. The first is the arrangement of fibres on the outside and inside of the yarn. The external structure includes the appearance and surface structure of the yarn. The external structure includes the appearance and surface structure of the yarn, such as the arrangement of fibres on the surface of the yarn; the hairiness of the yarn; the friction coefficient of the yarn; the characteristics of the yarn; the abrasion resistance of the yarn and other characteristics of the surface.
The internal structure of the yarn is mainly the entire cross-section of the fibres in the yarn body and the longitudinal arrangement of the yarn. Fibre orientation, elongation, displacement and twist internal structure include yarn strength; fibre mixing degree; bending strength; compressibility; and resilience (tendency to bond).
The above explanation of the meaning of structure is not necessarily complete but provides a complexity of yarn properties.
Spinning process
Comparison of yarn structure effects
In order to obtain the concept of spinning process influence on yarn structure apply 3dtex, 38 mm viscose staple fibre, test spinning in five different spinning process systems.
A\ conventional ring spinning process;
B\ Compact ring spinning process;
C\ double nozzle (MTS) pseudo-imaginary entanglement spinning process;
D\ Vortex spinning (MVS) spinning;
E\ Rotor spinning.
(1) The external structure of the yarn as mentioned above can be seen on a scanning electron microscope photogram. Application of microelectronic photography photos: including rotor spinning, air-jet spinning, vortex spinning, ordinary ring spinning and compact ring spinning five. The external fibre directionality of the yarns produced by the five processes can be seen in the photographs, where more fibres form the yarn in the external structure of the compact ring spun yarns. Almost all the fibres are formed in the yarn body, improved short fibre yarns, the twist structure of the yarns is seen clearly and one end of the fibres is flicked into the yarn body along the length of the yarn, the compact ring spun yarns have the best directionality .
(2) Conventional ring spun yarns, under the same twist conditions conventional ring spun yarns have a disturbed surface, a large number of fibre ends are not twisted into the yarn body, and individual fibres are sticking out of the body of the yarn, which may be due to the steel collar/wire ring or the yarn guide.
(3) Vortex spinning, approximating ring spinning, with fibres well aligned in the yarn body and fine spinning of entangled fibres at a spinning speed of 350/min. The twist rate is basically the same as ring spun yarn, the actual twist of the yarn is basically the same as the calculated twist. The ratio of entangled fibres to the core fibres of the untwisted yarn is very high and almost completely covers the core fibres. Therefore, the appearance of vortex yarn is basically similar to that of ring yarn, and the external entangled fibres form a true twist together with the untwisted core.
(4) Double nozzle false twist yarn and vortex yarn is actually different in nature, double nozzle jet yarn entangled fibres only accounted for all the fibres of 6% -8% about 90% of the fibres are stretched untwisted, it can be clearly seen that the entangled fibres of the core of the entanglement of the tightness of the yarn than the vortex yarn.
(5) Rotor spinning, regardless of whether the rotor yarn belongs to the category of true twist, but the rotor yarn on the fibre arrangement disorder, the fibres in the middle of the yarn show Z and S direction is not clear spiral, the fibres are straight. The fibres are straight. It can be clearly seen that the wrapped yarns are not tangled, which is the advantage of the rotor yarn and the basis of the rotor yarn characteristics.
Comparison of yarn properties
Different yarn twisting processes produce different yarn structures and product characteristics.
Yarn strength
Yarn strength depends on the holding and friction forces between the fibres. If the form of the fibres and their arrangement is poor, i.e. there are bent, looped, folded, twisted and other fibres, it is equivalent to shortening the length of the fibres, weakening the degree of contact of the fibres, and thus prone to inter-fibre slippage, reducing the strength of the yarn.
Tested that, such as ring yarn strength for 1, then other types of yarn strength for: rotor yarn 0.8 ~ 0.9, air-jet yarn 0.6 ~ 0.7, vortex yarn 0.8, compact spinning yarn strength up to 1.15.
Hairiness
The feel and characteristics of textile products are mainly determined by the amount of hairiness. From the production test can be clearly seen, the length of less than 2mm hair feathers on the production process and the appearance of the fabric quality has little impact. On the contrary, it gives the fabric a natural soft hand. However, hairiness of more than 3mm in length is a potential factor affecting yarn quality.
Compared to conventional ring yarns, airflow yarns, vortex yarns and compact yarns have a reduced hairiness of 1 to 2 mm. Air-jet yarns, on the other hand, have more short hairiness due to the low number of entangled fibres and the low coverage of the untwisted core. Of course, the amount of hairiness can be controlled by adjusting the process parameters specifically during the spinning process. Compared to conventional ring yarns, the number of harmful hairiness which higher than 3mm of non-traditional spun yarns is significantly reduced. The reduction is about 80% for compact yarns, 85% for air-jet yarns and more than 90% for vortex-spun yarns, resulting in good post-processing characteristics for all new yarns.
Due to the new yarn structure, the surface of the yarn is more stable and the increase in hairiness in post-processing is significantly lower than with conventional yarns. Especially as the warp yarn, in the sizing can save about 50% of the pulp, greatly improving loom efficiency, reduce weaving costs. In the United States, the use of new yarn per 100m cloth weaving cost can be reduced by 2.4 U.S. dollars, fly reduction of 72%.
Abrasion resistance
The abrasion resistance of yarn is closely related to the structure of yarn. Traditional ring yarn has poor abrasion resistance because most of the fibres are in the form of helix, and when repeatedly rubbed, the helix fibres gradually turn into axial fibres, and the yarn is easy to be untwisted and disintegrated, and is quickly worn off.
Non-traditional spinning yarn has obvious advantages in abrasion resistance. Rotor yarn, air-jet yarn and vortex yarn are made up of two parts: the core and the outer fibre, the surface of the yarn is wrapped with irregular winding fibres, which are not easy to disintegrate. At the same time, the friction coefficient of the yarn surface is large, and the holding between yarn and yarn in the fabric is good, and it is not easy to produce relative slippage, so the abrasion resistance is improved.
Compared with ring yarn, the fibre arrangement of compact yarn is neat and straight, the yarn structure is close, and the fibre is not easy to disintegrate, so the wear resistance of the yarn is good.
Twist
The degree of twist is also an important characteristic of the yarn and determines some of the characteristics of the fabric, e.g. the diagonal path of knitted fabrics. Conventional ring and compact yarns are spun with a true twist, which is high enough to produce slubs and crimps in knitted fabrics, and sometimes it is necessary to compensate for this by using parallel yarns.
The yarn structure of rotor yarn, air-jet yarn and vortex yarn determines its small twist. Rotor yarns have both Z-twist and S-twist and therefore have the lowest twist. Air-jet yarns also have good post-processing properties due to the high proportion of parallel fibres and low twist back.
Pilling resistance
Knitted fabrics made from vortex yarns have good abrasion resistance and a high level of pilling resistance. This is due to the flat core yarns in the middle of the swirl yarns and the winding fibres in the outer layer, which have a clear fibre orientation and a high coefficient of yarn friction. The friction between yarns within the fabric is good, and it is not easy to produce relative slippage, and the abrasion resistance is improved. In addition, pilling is also closely related to the hairiness of the yarn. Through the test pilling test can be seen, vortex yarn fabric 4 ~ 4.5 level, air-jet yarn 4 level, traditional ring yarn 2 level, rotor yarn 2 ~ 3 level, compact spinning yarn 3 ~ 4 level.
Hairiness
The formation of flecks and hairiness in spinning is a very problematic issue. Hairiness has many negative effects in downstream processing and the feel of the textile and the nature of the end product are affected by hairiness. A hairiness test is used to classify 1mm-2mm hairiness and to separate out harmful hairiness above 3mm. If the hairiness of ring spinning yarn is 100%, the 1mm-2mm hairiness of compact ring yarn, swirl yarn and rotor yarn is less than that of ring yarn, and the double nozzle false-twisted wrapped yarn, which is in poorer wrapping condition, has more hairiness. Measurement of fly formation due to friction when the yarn is processed in the post-process, the friction is measured with a rubber ring. Compact yarns have better anti-friction properties than non-traditional yarns. Rotor yarns stick out with fewer hairinesses, especially more pronounced in viscose fibres, and the fibres on the yarn do not break. However, many of the hairiness is entangled in the body of the yarn by the wrapped fibres, so the rotor yarn has less hairiness.
Yarn Volume
Yarn volume is an important index reflecting the covering ability of yarn, compact spinning ring yarn and ordinary ring yarn in the same twist, the latter end product covering ability is lower. Compact spinning ring yarn can reduce the twist to increase the yarn volume under the condition of maintaining the same strength, which can obtain the covering capacity equivalent to that of ordinary ring yarn, and the twist can be reduced by 5% to 10%. The yarn structure tester can provide the measured yarn volume with a yarn length of 0.3mm. Yarn volume testing includes double nozzle MJS air-jet yarns of the same yarn count. Since air-jet yarns are wrapped and false-twisted, they have a higher volume than ring-spun yarns of the same yarn count. Graphics taken with micro-electron scanning photography show that a small number of entangled fibres are in the core and are so short that many parts of the yarn are essentially untwisted.
The fibre arrangement of an ideal compact ring yarn is shown to be superior to that of a normal ring yarn. All non-traditional spinning techniques have shortcomings, and this new type of spinning must be treated when making warp yarns. In air-jet spinning technology, there are few fibres on the yarn with straightening and winding as opposed to true twist yarns. As a result, the mechanical and physical properties of the yarn vary, especially when winding, which is still the difference between non-traditional spinning and ring-spun yarns.
Yarn internal structure
The formation of fibres inside the yarn is related to the external structure of the yarn. The arrangement of the yarn cores inside the yarn and the fibre extension along the yarn length can be obtained by scanning electron photography during drafting. The fibres are highly parallel as seen in the yarn cross-section and influence the yarn strength. Yarn strength characteristics are related to the clamping length during the test.
Reduced details and the possibility of weak loops in the strength: Normal yarn strength is tested on a 520 mm clamping length machine, also with 100 mm and 18 mm clamping lengths. A decrease in clamping length increases the breaking strength of the yarn due to the fact that a shorter clamping length reduces the likelihood of weak loops and details, and a lower breaking length reduces the chance of breakage. If the fibre distribution is well oriented, the test clamping length decreases and the yarn breaking strength increases significantly, more so for ring and compact ring yarns. The breaking strength of rotor yarns is lower, even if the breaking length is lower than the fibre length, due to the formation of curved hooks in the fibres, the breaking strength of rotor yarns does not increase even if the breaking length is short. In conclusion, the more the yarn fibres are clamped, the better the longitudinal orientation of the fibres and the higher the breaking strength of the yarn. From the scanning electron photography, it can be seen that the rotor yarn is a twisted structure. Even if the clamping length is lower than 5 mm, 100% of the fibres are clamped and the fibres break; the clamping length is 0 mm, the fibre breakage length is lower than the fibre length, and the core fibre orientation is poor, resulting in low breaking strength.
Air-jet yarn strength between ring yarn, compact yarn and rotor yarn, mainly air-jet yarn, yarn core than rotor yarn parallel, less entangled fibres, strength than rotor yarn less high.
Yarn formation affects yarn deformation
For example, yarn bending resistance is the characteristic that is affected during yarn formation, but the detection of yarn bending resistance is difficult. An up-to-date method for detecting yarn bending resistance has been developed. Tests have shown that if the bending strength of compact yarns is 100 per cent, then it is 200 per cent for rotor and vortex spinning and 300 per cent for double nozzle air-jet yarns. These numerical relationships can be compared with ring-spun yarns from a number of non-traditional spun yarns, on woven and knitted fabrics. The fabrics of the non-traditionally spun yarns have a coarser and stiffer feel than the normal ring yarn products, and there is a small difference in bending strength between the normal ring yarns and the compact yarns.
Another problem arises when the yarn deformation in the warp and weft cross-section of the yarn under pressure to become flat deformation of the situation. The detection of thick knots in the yarn showed that the thick knots decreased when the compression force of the yarn was increased.
The yarn structure of the rotor yarn causes the fibre distribution condition, where the fibres are entangled, the hand is harder and the deformation force is smaller than that of the yarn without entanglement. Knitted fabrics and woven fabrics produced by rotor yarns tend to make an uneven, coarse and hard appearance than ring yarns.
In order to make a comparison, the yarn thick knots in 1OOcN pressure conditions test, indicating that the yarn has the best twist structure, the same deformation of the MTS double nozzle air-jet yarn in about 95% of the parallel untwisted fibres, it is more likely to produce deformation, according to this test, the rotor yarn feel harder, in the loom or knitted fabric appearance can be detected by the yarn’s tightness of the deformation of the yarn.
Resilience of yarns
The resilience of yarns is very important for textile processing, e.g. skewed deformation of knitted fabrics. The resilience is measured by detecting the yarn knotting force, the resilience of compact ring yarns, normal ring yarns and other real twisted yarns is different from that of non-traditional yarns, and the knotting of rotor yarns that are positively or negatively twisted is lower.
The lower resilience of air-jet spun yarns is mainly due to the higher proportion of parallel untwisted fibres, and the real twisted yarns have higher resilience than the non-traditional yarns, so the fabrics are less skewed when they are further processed into knitted fabrics.
Conclusion
Yarn structure is one of the important properties of yarns. The yarn’s appearance is related to the yarn properties, and the internal fibre arrangement of the yarn has a great influence on the yarn properties. The internal fibre arrangement of the yarn has a great influence on the yarn properties, especially on the further processing of the yarn and on the properties of the final product. Poor yarn structure has a great influence on post-processing, good yarn structure has a particularly good function and use, in the adaptability of textiles with compactly spun yarns, the appearance of the structure is the most desirable.