Yarn fineness index
The fineness index of spinning yarn is the same as that of fiber and can be divided into two categories: direct index and indirect index. Direct indicators refer to diameter, cross-sectional area, circumference, etc. For fibers and yarns, it is more troublesome to measure direct indicators. Therefore, except for wool fibers, which use diameter to express the thickness of the fiber, other fibers and yarns generally do not use direct indicators such as diameter to express it. When direct indicators are needed in fabric technology, they are converted using indirect indicators. Indirect indicators use the relationship between the length and weight of spinning yarn to express linear density, and are divided into two types: fixed length system and fixed weight system. The fixed-length system refers to the standard weight of a certain length of fiber and spinning yarn; the fixed-weight system refers to the length of a certain weight of fiber and spinning yarn. The indirect indicators of the fineness of spinning yarn include linear density (Tt), denier (Ndem), metric count (Nm) and imperial count (Ne). The concepts and calculations of linear density, denier and metric count are the same as those of fiber. Please refer to the chapter. This section only provides examples. Example 1 It is known that the weight of a pure cotton yarn measured under the public moisture regain is 50g and the length is 2500m. What are its linear density Tt and denier Ndem? Solution: Substitute the known quantities into the formula. (1-9) and formula (1-10), that is: The test of indirect indicators of yarn fineness in production usually adopts the yarn weighing method. Use a yarn length measuring instrument to wind a certain length of spinning yarn (generally 100M for cotton yarn, 50m for combed wool yarn, and 20m for carded wool yarn). After drying in an oven, weigh the total number of skeins. If it is heavy, various fineness indicators can be obtained according to the definitions of each indirect indicator. (1) Expression and calculation of the fineness of the strand The fineness of the strand is expressed by the combination of the single yarn fineness and the number of single yarns n. When the fineness of the single yarns that make up the strands is expressed in terms of linear density, if the linear densities of the single yarns that make up the strands are the same, the fineness of the strands is expressed as: Tt strand=T t×n (2-2) If the single yarn densities that make up the strands are different, it is expressed as:
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