Textile fibers generally refer to objects with a diameter of several microns or tens of microns, and a length many times larger than the diameter. They can be used to process and manufacture textiles and are characterized by their thinness and length. Textile fibers must have a certain fineness and length so that the fibers can cohere with each other and be spun into yarn relying on the friction between the fibers. This is also one of the necessary conditions for textile processing and making products valuable.
Length is one of the main quality indicators of fiber materials and an important factor in determining the spinning value of fiber materials.
Relationship between fiber length and yarn quality
Fiber length is closely related to yarn quality. Mainly manifested in the following aspects:
1. Fiber length and yarn strength In yarn, if the fiber length is longer, the contact length between fibers will be longer. When the yarn is acted upon by external force, the fiber will not easily slip off. At this time, the yarn will be The number of fibers that pull and slip is smaller, so the yarn strength is higher. Changes in fiber length have different effects on the rise and fall of yarn strength. When the length of the fibers that make up the yarn is short, the length has a relatively greater impact on the strength of the yarn. Among the commonly used textile fibers, the length of cotton fiber is shorter. Therefore, its length has a greater impact on the strength of the yarn. Fiber length uniformity also affects yarn strength. When the short staple ratio of raw cotton is higher than 15%, the yarn strength will decrease significantly.
2. Fiber length and yarn density. There is a limit value for the yarn density of fibers of various lengths. On the premise of ensuring that the finished yarn has a certain strength, the longer the fiber length, the smaller the ultimate linear density of the spun yarn, that is, the thinner the spun yarn; the shorter the fiber length, the greater the ultimate linear density of the spun yarn. , that is, the thicker the yarn being spun. For example, fine velvet cotton with a length of less than 25mm can generally only spin medium and thick special yarns with a length of more than 30tex; for fine velvet cotton with a length of about 29mm, the limit linear density of yarn spun is 10tex. If you want to spin less than 10tex Fine yarn must be made of long-staple cotton. The longest fiber of long-staple cotton can be spun into fine yarn up to 3tex.
3. Fiber length and yarn evenness: The longer the fiber length and the higher the length uniformity, the better the spun yarn evenness. When the fiber length is very short and the length uniformity is poor, the evenness becomes poor and the yarn quality decreases.
4. Fiber length and yarn hairiness: When the fiber is longer, the fiber head end on the yarn is less exposed, the yarn has less hairiness, and the surface is smooth. On the contrary, the yarn surface has more hairiness. Fiber fineness reflects the degree of fiber thickness. Like length, fiber fineness is also non-uniform.
Fiber fineness and yarn strength
When other conditions remain unchanged, the finer the fiber, the higher the yarn strength, and the finer the spinnable yarn. This is because the fibers are thin, the cross-section of the yarn contains a large number of fibers, the contact area between fibers is large, the chance of slippage between fibers is small, and the strength of the yarn is high. Cotton fibers have thinner fibers (extremely low single fiber strength) due to thin walls and poor maturation, and the strength of the yarn is reduced.
Fiber fineness and yarn evenness
Generally, the finer and more uniform the fibers are, the greater the number of fibers in the cross-section of the yarn, and the better the evenness of the yarn. Especially when spinning a thin yarn with a small number of fibers in the yarn, using finer fibers will have a particularly significant effect on increasing the strength of the yarn and improving the evenness of the yarn. The fiber length is also closely related to the spinning process. From the structure and size of the spinning equipment to the process parameters of each process, everything must match the fiber length used. For example, when the length of raw cotton is different, the beater form of the cleaning machine and the length of the cotton feeding plate of the carding machine should be changed. The roller spacing in the cotton spinning machine can be adjusted. When the fiber length is long, the roller spacing increases. When the fiber length is short, the roller spacing decreases. The twist coefficient of spun yarn should also change with the change of fiber length. In order to make the spun yarn have a certain strength, when spinning with short fibers, the twist coefficient of the spun yarn should be larger; when spinning with long fibers, the twist coefficient of the spun yarn should generally be smaller. The twist coefficient is low, which can increase the output of the spinning frame.
Because of this, different fiber lengths require different process parameters for the corresponding spinning process.
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