The quality of yarn for knitting shall meet the following requirements!

Knitting requires higher evenness (i.e., uniform thickness of yarn), good softness, a certain level of strength and extensibility, and relatively low twist. During the formation of knitted fabrics on knitting machines, yarns are subjected to complex mechanical stresses such as stretching, bending, twisting, and friction. To ensure smooth production and high-quality end products, yarns for knitting must meet the following requirements:

1. Yarn shall possess adequate strength and extensibility
   Strength is a critical quality index for knitting yarn. Since yarns endure constant tension and repeated loading during preparation and weaving processes, they must have a certain degree of strength. In addition, yarns undergo bending and torsional deformation during loop formation in knitting. Therefore, knitting yarns are also required to have a certain level of extensibility, which facilitates loop formation and reduces yarn breakage.
2. Yarn shall have good softness
   Knitting yarn demands higher softness than weaving yarn. Soft yarns are easier to bend and twist, which contributes to uniform loop structure and a clear, attractive appearance of the knitted fabric. Meanwhile, it can reduce yarn breakage during weaving and minimize damage to looping components.
3. Yarn shall have an appropriate twist
   Generally speaking, the twist of knitting yarn is lower than that of weaving yarn. Excessively high twist will reduce yarn softness, making it hard to bend and twist during weaving. It may also cause yarn snarling, leading to fabric defects and damage to knitting needles. Moreover, over-twisted yarn will impair the elasticity of the knitted fabric and result in loop distortion. However, the twist of knitting yarn cannot be too low either; otherwise, its strength will be compromised, increasing breakage during weaving. Additionally, low-twist yarn tends to be bulky, making the fabric prone to pilling and reducing its wearability. Therefore, selecting the right twist is a key step in rational yarn selection. Twist requirements vary depending on the intended use of the knitted fabric.
   • Jersey fabric requires smoothness, compactness, a clean surface, and distinct texture, so the yarn twist should be relatively high—close to the standard twist of warp yarn for weaving with the same linear density.
   • Yarn for outerwear should have a higher twist to enhance fabric stiffness and improve pilling resistance.
   • Interlock fabric and stretch fabric demand a soft hand feel and good elasticity, so the yarn twist should be slightly lower, generally adopting the lower tolerance limit of the twist of weft yarn for weaving with the same linear density.
   • Yarn for fleece-knitted fabrics requires an even lower twist to facilitate napping and ensure uniform pile thickness.
   In addition, the optimal twist level also varies with the linear density of the yarn.
4. Yarn shall have uniform linear density and minimal defects
   The uniformity of yarn linear density, i.e., yarn evenness, is a crucial quality index for knitting yarn. Yarn with consistent evenness is conducive to smooth knitting processing and high fabric quality, ensuring uniform loop structure and a clear fabric surface. Coarse slubs on yarn will hinder knitting operations, causing yarn breakage or damage to machinery parts, and may form horizontal stripes or clouding defects on the fabric surface, degrading product quality. Thin places on yarn, on the other hand, have insufficient strength, which easily leads to breakage, affecting fabric quality and reducing machine productivity. Since knitting machines have multiple feeding systems for simultaneous loop formation, it is not only required that the yarn in each feeding path has uniform thickness, but also that the thickness difference between yarns of different paths is strictly controlled. Otherwise, horizontal stripes and shadow defects will appear on the fabric, lowering its quality.
5. Yarn shall have good hygroscopicity
   Hygroscopicity refers to the ability of yarn to absorb moisture from the air. Different fibers vary greatly in hygroscopic capacity, and the moisture absorption amount changes with ambient temperature and humidity. Yarn used for knitting should have moderate hygroscopicity. Under the same relative humidity conditions, yarn with good hygroscopicity not only has better electrical conductivity, but also helps stabilize yarn twist and improve extensibility, thereby enhancing its knitting performance.
6. Yarn shall have good smoothness and a low friction coefficient
   Knitting yarn should be free of impurities and oil stains as much as possible and have a smooth surface. Rough yarns will cause severe wear to machinery parts, leading to equipment damage. They also generate more flying fibers in the workshop, which are harmful to workers’ health and will reduce the productivity of knitting machines and the quality of the final fabric.