Short fiber is one of the key factors affecting the quality of cotton spinning. Under the same process conditions, the less the short fiber content, the higher the yarn breaking strength and the better the yarn quality.
Production of short fibers
Short fiber is a fiber in cotton fiber whose length is shorter than a certain limit of the length of the main fiber. It is commonly expressed as the percentage of short fiber mass to the total fiber mass, which is called short staple rate. There are two main reasons for the production of short fibers: the first is produced when the fiber itself grows. When blending with cotton, the raw materials contain more lint, especially short velvet with a short length (below 12mm); the second is the fiber Damage during processing, short lint produced during the blowing and carding process after opening, beating and carding.
The length of short fiber: abroad, the fiber length specified by Uster is mainly 10mm. In addition, the UK and Switzerland use fiber lengths below the average length as short fiber; domestic quality Control generally uses fiber lengths below 12.7mm and 16mm for analysis. Short fibers of different lengths have different effects on the spinning process. Short fibers of 4mm to 5mm are generally lost during the spinning process; short fibers of 12mm to 15mm can only fill the yarn to achieve a full effect. Does not contribute to strength; fibers above 16mm have a positive impact on the internal and external characteristics of the yarn.
Short fibers tend to form a large number of neps during the blowroom and carding processes, which reduces fiber quality and increases waste and cotton costs; during combing and roughening During the processing process, short fibers are difficult to control and form floating fibers, which affects the fiber speed change; during the twisting process, short fibers easily protrude from the surface of the yarn body, forming hairiness and affecting the style of the cloth surface.
Impact on yarn quality
The impact of short fibers on yarn quality is due to the fact that short fibers are difficult to completely remove and control during the spinning process. Although some short fibers will fall along with impurities during the blow blowing and carding processes, there is still a considerable part of the short fibers that become part of the card sliver. During the drafting process, they are not held by the rollers and become free fibers. The thick places and details of the yarn, as well as the unevenness of the yarn, result in an increase in yarn breakage, a decrease in yarn strength, a decrease in single yarn elongation, and an increase in yarn breakage, which affects the appearance of the cotton fabric.
During the drafting process, short fibers are not easily controlled by the drafting mechanism and appear in a “floating” state. Their irregular movement will affect the frequent yarn defects in the finished yarn. Relevant data shows that for every 2% increase in the short staple rate of C18.2tex yarn below 12.7mm, the corresponding CV value of the yarn will increase by 1%. In the raw cotton of fine yarn, if the short staple rate below 10mm increases by 2%, the CV value of the yarn will increase by 1%. At the same time, the common yarn defects (neps, thick places and details) will also increase to varying degrees. increase.
Short fibers are difficult to control during the production process and are often in a floating state. Flying and edge fibers appear, causing slub and detail yarn defects. The higher the short fiber rate, the more likely it is that occasional yarn defects will occur. The increase is more obvious.
The higher the short staple content, the lower the yarn strength and the higher the strength unevenness; the higher the short staple content, the poor transverse cohesion and longitudinal hooking capabilities of short fibers. It is easy to break when subjected to tension, which affects the strength of the yarn. The higher the short fiber content, the more fibers there are in the cross-section of the yarn, and the more the ends and tails are, which can easily protrude from the main body of the yarn, and the greater the possibility of causing yarn hairiness. At the same time, during the winding and unwinding process, hairiness will increase sharply under the action of high-speed and severe friction. Therefore, strengthening the control of short fibers has positive significance for improving yarn quality. </p
