As the main raw material of textile mill, cotton occupies a large proportion in the total textile cost. It is proved that the quality of cotton fiber is directly related to the quality of textile products. The most important indexes to determine the quality of cotton yarn are cotton fiber length, length uniformity, staple fiber content, moisture regain, harmful defects, foreign fiber, specific strength and cotton fiber fineness.
Cotton fiber length
The length of cotton fiber is a main physical index of raw cotton quality, and also the main factor of textile use value. The longer the cotton yarn is spun, the longer the fiber overlaps with each other in the cotton yarn, and the stronger the spun yarn is. Under the same other conditions, the longer the fiber is, the higher the yarn strength will be, and the finer the yarn count will be. The fiber is long and neat, the friction force between the fibers is large, the slippage is difficult, and the yarn evenness is good. When spinning fine count yarn with high strength and long length fiber, it has significant effect on improving yarn strength. Therefore, the length of cotton fiber is closely related to yarn strength. In the spinning process, the adjustment of the roller spacing and the twist factor of coarse and fine yarns are all related to the length of cotton fiber. As the fiber length is the main basis for determining the spinning process and equipment, the spinning process factors such as roller gauge, pressure, draft ratio and twist have an impact on the yarn evenness.
regain
Moisture regain is the main factor affecting cotton processing quality. The moisture regain of lint after processing also has a great influence on the spinning of textile mills. The moisture regain rate of raw cotton is high, the cotton block is not easy to loosen, and the layer by layer is bonded, which is easy to cause uneven lap. The carding efficiency of carding machine is low, the cotton web is easy to sag, the evenness of sliver is poor, the moisture regain of raw cotton is too low, the fiber is easy to be interrupted and damaged in the process of processing, resulting in the increase of short fibers and the increase of static electricity, resulting in "dry winding" phenomenon in cots, rollers, aprons and other parts. Therefore, the moisture regain of cotton for textile should be controlled at 7% - 9%.
Impurities in raw cotton
Impurity content in raw cotton is one of the main factors affecting yarn quality. There are three types of impurities in raw cotton. The first category is impurities that are easy to remove, such as leaf sediment and cottonseed; the second category is the impurities that are easy to be broken and difficult to remove, which have a great impact on the gauze, such as sterile seeds, rod chips with fiber, broken seeds, etc.; the third category is the harmful defects that are difficult to remove and have obvious harm to the quality of gauze, such as soft seed epidermis, stiff sheet, yellow root and foreign fiber Etc. The quality of rolling is also a factor affecting the yarn quality. If the cotton is not well rolled, the resulting strands and neps, especially the tightly wound ones, are difficult to be combed and eliminated, resulting in more neps and impurities in the yarn.
