Yarn strength refers to the maximum tensile external force that the yarn can withstand, and it is stretched to break by external force. Adding a certain twist to the yarn can increase its fastness, but the greater the twist, the better. So how to improve the strength of the yarn?
Reasonable selection of raw materials
Raw material properties such as length, linear density, breaking length, maturity, short fiber content, etc. have a great impact on yarn strength. The fiber length is long, the uniformity is good, and the linear density is small. The more fibers per unit section, the higher the twisting efficiency, the higher the yarn strength and the smaller the strength unevenness; the larger the linear density unevenness, the lower the yarn strength.
Generally speaking, when the fiber length is relatively short, the increase in length will significantly improve the strength of the yarn; when the fiber length is long enough, the effect of length on the strength is not very obvious; the better the uniformity of the fiber length, the higher the strength of the yarn. . Under the same spinning characteristics, the finer the fiber used for spinning, the higher the yarn strength.
Control the quality of semi-finished products
1) Reasonable selection of opening and impurity removal process parameters in the blowing and carding process. Under the premise of sufficient opening and carding, excessive fiber damage is avoided and short lint and impurities are eliminated as much as possible. Reduce the generation of short fibers in the carding machine’s licker-in part. When the cylinder and cover plate working areas adopt the process principle of “tight spacing and strong carding”, the carding efficiency can be fully exerted and the knots and short fibers can be eliminated. The effect is beneficial to improving the strength of the yarn.
2) The drafting process and drafting form should be reasonably configured in the drawing process and roving process to ensure the control of fibers during the drafting process and improve the straightening and parallelism of the fibers. In addition, the temperature and humidity of the roving should be appropriately increased to increase the moisture regain of the roving, which will facilitate the disappearance of fiber stress and ensure straightening. Reducing the drafting distance can stabilize the fiber movement and produce rovings with uniform evenness and good structure. To improve the short segment unevenness of the roving, the weight of the final bundle should be strictly controlled, the table difference, eye (head) difference should be reduced, the roving winding elongation spindle difference caused by the weight difference of the fiber strips should be reduced, and the roving elongation should be reasonably controlled. In addition to controlling temperature and humidity in the roving process, the roving winding tension should be appropriate, but the winding density should not be too small; the roving twist coefficient should be reasonably designed according to the quality characteristics of different products.
3) To improve the strength of the yarn, the drafting process of the spun yarn should focus on improving the uniformity of the spun yarn. The greater the unevenness of the spun yarn, the lower the strength.
4) Reduce the property difference rate of raw materials, enhance the uniform mixing of raw materials in pre-spinning, improve the carding effect to increase the mixing between single fibers, increase the number of combinations of combing and drawing processes, etc., so that each raw material component is evenly distributed in the yarn, This enables the strength of each fiber to be reasonably and fully utilized during the stretching process of the yarn.
5) Control the quantitative difference of cooked strips, reduce the spindle difference in winding elongation, strengthen equipment maintenance and basic management, and reduce the occurrence of weak loops.
Optimize yarn evenness and structure
Optimize the yarn structure, such as the straightness, parallelism and arrangement and distribution of fibers in the yarn, the twist size of the yarn, the tension, width, tightness, fiber arrangement and straightening before twisting, etc., which have an impact on the strength of the yarn. All have a certain impact.
Yarn evenness, such as weight unevenness, evenness and twist unevenness, affects the evenness of spun yarns, mainly due to the process of the front zone and the reasonable distribution of the friction zone, the distance of the front drafting zone, and the floating zone. The length, the size of the apron jaws, etc. can reduce the yarn weight unevenness by controlling the yarn weight unevenness within 100 meters within 2%, the cotton roll unevenness within 1%, and the combed short staple rate within 8%.
Control yarn weight unevenness
The CV value of the yarn weight per 100 meters is an important factor affecting the strength of the bobbin. Generally, the unevenness of spun yarn weight must be stable within 2% to avoid sudden CV values exceeding the standard. However, sometimes the single yarn strength unevenness is high, but the 100-meter weight CV value does not show up. This is due to the occurrence of “sudden strength” yarn segments, which are often only about 0.5 m. This requires reducing the unevenness of the long segments of the spun yarn, while It is also necessary to reduce the segment unevenness of about 0.5 m.
Conclusion
To improve the yarn strength, we should start from the aspects of rational selection of raw materials, reducing mixing differences, improving the quality of pre-spinning semi-finished products, improving the structure of semi-finished products and finished yarn, improving the evenness of spun yarn and rationally selecting the twist coefficient.
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