The titer of the core filament and the number of monofilaments in it should be selected according to the fabric use and the number of spinning threads. For the same titer core filament, the finer the monofilament, the more the number of roots, the softer and smoother the fabric, and the less the number of roots, the better the rigidity and crispness of the fabric. For the covered product, there is no need to consider the gloss of the core filament, and the glossy core filament can be used to reduce the production cost; if the exposed product is produced, the gloss of the core filament should be considered, and the bright filament should not be used as much as possible, so that the product will cause aurora and affect the use effect. For example, in the production of 11.8tex (50s) polyester-cotton core-spun yarn for skirts and shirt fabrics, it is advisable to use ordinary low-strength and high-elongation 5.56tex (50D)/24F semi-glossy polyester filament as core yarn. When the core spun yarn is used as sewing thread, the high-strength and low-elongation glossy polyester filament with a large number of monofilaments above 7.78tex (70D)/36F is generally selected. When used as a rotten outerwear fabric, glossy polyester filament below 7.56tex (68D)/36F can be used. However, for the core spun yarn of rotten flower fabrics, the titer of the core filament should be too large to master, generally using 7.22-8.33tex (65-75D)/36F matte or semi-gloss polyester filament, in case the rotten part is too thin, too thin and causes aurora. The core yarn used in stretch fabrics can be selected according to the fabric application. Generally, polyester 7.78tex (70D) spandex yarn is used, and its drafting multiple is about 3.8 times. The medium (medium and low-count) spandex core-spun yarn for warp strength corduroy and elastic labor cloth has a larger spandex wire draft, about 3.8-4.0 times, which can ensure that the buttocks and knees have a relatively high resilience when the elastic pants are taken. 2.2 Selection of outsourced fibers.
If cotton fiber is used for outer fiber, theoretically speaking, raw cotton with long length, high count count and good maturity should be selected as much as possible. However, depending on the use of the product, if it is not a high-speed sewing thread, but a shirt fabric or skirt, or other rotten decorative fabrics, there is no need to choose good raw cotton, because they do not need to withstand the test of strong friction and high-temperature melting like high-speed sewing thread, and will not produce the phenomenon of "peeling", so the use of 30mm long raw cotton can meet the requirements. However, the outer cotton used as a core-spun yarn for rotten fabrics has fewer nep impurities. If cotton is selected as the outer fiber, it is better, with low strength, good dyeing performance and less nep impurities.