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Analysis of the Influence of Fiber Length and Fineness on Yarn Quality

2019-04-21

【Technical Interpretation】Analysis of the Influence of Fiber Length and Fineness on Yarn Quality

Textile fibers generally refer to objects that are several microns or tens of microns in diameter and many times longer than the diameter. Objects that can be used to make textiles are characterized by thinness and length. The textile fibers must have a certain degree of fineness and length in order to allow the fibers to entangle each other and to be spun into yarns depending on the friction between the fibers. This is also one of the necessary conditions for textile processing and the use of the product.

 

Length is one of the main quality indicators of fiber materials and is an important factor in determining the value of fiber material spinning.



1 Fiber length and yarn quality

 

The relationship between fiber length and yarn quality is very close. Mainly in the following aspects.

a) Fiber length and yarn strength In the yarn, if the fiber length is long, the contact length between the fiber and the fiber is long, and the fiber is not easily slipped when the yarn is subjected to an external force, and the yarn is affected by the yarn. The number of fibers that are pulled and slipped is small, so the yarn strength is high. The change in fiber length has a different effect on the rise and fall of the yarn strength. When the length of the fibers constituting the yarn is short, the effect of the length on the yarn strength is relatively large. Among the commonly used textile fibers, the length of the cotton fiber is short, and therefore, the length thereof has a relatively large influence on the yarn strength. The uniformity of the fiber length also has an effect on the yarn strength. When the rate of linters in the raw cotton is higher than 15%, the yarn strength will decrease significantly.


b) Fiber length and yarn density The spinning yarn density of various length fibers has a limit value. Under the premise of ensuring a certain strength of the yarn, the longer the fiber length, the smaller the limit linear density of the spun yarn, that is, the finer the spun yarn; the shorter the fiber length, the greater the limit linear density of the spun yarn. That is, the thicker the yarn is spun. For example, fine cotton with a length of 25 mm or less can only be used for spinning medium and thick special yarns of 30 tex or more; fine cotton with a length of about 29 mm, the limit linear density of the spun yarn is 10 tex, if it is to be spun below 10 tex For spun yarn, long-staple cotton must be used. The longest fiber of long-staple cotton can be spun into 3tex spun yarn.

 

c) Fiber length and dryness uniformity of the yarn. The longer the fiber length and the higher the uniformity of the length, the better the yarn is dried.

 

When the fiber length is short and the length is neat, the strip is deteriorated and the quality of the yarn is lowered.

 

d) Fiber length and yarn hairiness When the fiber is long, the fiber end of the yarn is exposed less, the yarn has less hairiness, and the surface is smooth. On the contrary, the surface of the yarn is more hairy. The fineness of the fiber reflects the degree of the fiber thickness, and the fiber fineness is also uneven as the length.

 

2 Fiber fineness and yarn strength

 

When the other conditions are constant, the finer the fiber, the higher the yarn strength, and the finer the fineness of the spinnable yarn. This is because the fibers are fine, the number of fibers contained in the yarn-forming cross section is large, the contact area between the fibers is large, the chance of slippage between the fibers is small, and the yarn forming strength is high. When the fiber of the cotton fiber is thin due to the poor maturity of the wall (the fiber strength is extremely low), the yarn strength is rather reduced.

 

3 Fiber fineness and yarn evenness

 

Generally, the finer and more uniform fibers are, the number of fibers in the yarn-forming section is large, and the uniformity of the yarns is better. In particular, when the number of fibers in the spun yarn is originally small, the finer fiber is used, and the effect of improving the yarn strength and improving the yarn drying is particularly remarkable. The relationship between fiber length and spinning process is also very close. From the structure and size of the spinning equipment to the process parameters of each process, it must match the length of the fiber used. For example, when the length of the raw cotton is different, the beating form of the cleaning machine, the length of the cotton feeding board of the card, etc. should be changed. The roller gauge in the cotton spinning machine can be adjusted. When the fiber length is long, the roller gauge is increased, and when the fiber length is short, the roller gauge is reduced. The twist factor of the spun yarn should also vary with the length of the fiber. In order to make the spun yarn have a certain strength, when the spun yarn is spun with a short fiber, the twist coefficient of the spun yarn should be selected to be large; when the spun yarn is spun with a long fiber, the twist coefficient of the spun yarn is generally small. The low twist factor increases the yield of the spinning frame.

 

Because of this, the length of the fiber is different, and the corresponding spinning process should adopt different process parameters.

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