Due to the development of denim varieties, different types of denim have different requirements for the quality of the yarns used. The basic requirements are as follows:

When selecting cotton fibers to achieve better dyeing performance, denim manufacturers should choose cotton with better maturity and less impurities. The yarn is necessary to have good leveling and permeability. If the maturity of the cotton fibers is poor or the fibers contain dead cotton, after the warp yarns are dyed, severe dyeing unevenness will occur, affecting the color light and causing streaks or color spot dyeing defects.

2. During the weaving process of denim, to achieve all the necessary stable weaving states for the denim style, denim manufacturers usually choose a relatively large on-machine tension and need to withstand multiple opening stretching. Therefore, the warp yarn is required to have high strength and excellent elasticity.

3. The requirements for the dryness and defects of weft yarns in denim are stricter than those for warp yarns. When the evenness of the weft yarn is large or there are many defects in the bamboo joint yarn, it will result in low yarn strength and a large unevenness rate of strength, which seriously affects the surface style and appearance quality of the denim. When the weft yarn has severe bamboo knots, it will form faintly visible white streaks on the fabric surface, which is detrimental to the distinctive "blue with white" style of denim fabric. Therefore, denim manufacturers require that the yarn be evenly spaced and have few defects.

4. The yarn should have few fuzz. Excessive fuzz can also cause unclear openings in the warp yarns during weaving, affecting the style of the fabric surface.

5. The joints of the yarn are few and small. Denim is generally arranged in a 3/1 right twill pattern. The knot ends of the warp yarns are relatively exposed on the fabric surface, forming a black or white spot that does not match the color of the fabric surface, thus creating a defect. Although the knots and defects of weft yarns are not as obvious and easily exposed as those of warp yarns, which may affect the appearance quality of the product, too many knots can also cause scattered white star defects on the fabric surface. One of the advantages of rotor spinning is that it has a large roll capacity and fewer knots than ring spinning.