What are the quality requirements for knitted yarn? Knitting requires a higher degree of evenness (i.e., the thickness uniformity of the yarn), good softness, certain strength and elongation, and low twist (yarn twist is relatively low). During the process of forming knitted fabrics on a knitting machine, the yarn is subjected to complex mechanical effects such as stretching, bending, twisting, friction, etc. To ensure normal production and product quality, knitted yarn should meet the following requirements:Knitted yarn
1. Yarn should have a certain strength and elongation
The strength of yarn is an important quality indicator for knitted yarn. Due to the tension and repeated loading of yarns during preparation and weaving, knitted yarns must have a certain strength. In addition, during the process of weaving into loops, the yarn also undergoes bending and twisting deformation, so it is also required that the knitted yarn has a certain degree of elongation to facilitate the bending into loops during the weaving process and reduce yarn breakage.
2. Yarn should have good flexibility
The softness of knitted yarn is higher than that of woven yarn. Because soft yarns are easy to bend and twist, and make the coil structure in knitted fabrics uniform, with a clear and beautiful appearance, it can also reduce yarn breakage and damage to loop forming parts during the weaving process.
3. The linear density of the yarn should be uniform and there should be fewer yarn defects
The uniformity of yarn linear density, also known as the dryness of yarn lines, is an important quality indicator for knitted yarns. A uniform yarn is beneficial for knitting processing and ensuring fabric quality, making the coil structure uniform and the fabric surface clear. If there are coarse knots on the yarn, the weaving cannot pass smoothly, causing yarn breakage or damage to the machine parts, and it is easy to form "horizontal stripes" and "cloud spots" on the fabric surface, reducing the quality of the knitted fabric; If there are details on the yarn, the strength is insufficient at this point, making it prone to breakage, affecting the quality of the fabric and reducing machine productivity. Because there is a multi loop system on the knitting machine that simultaneously feeds yarn into loops, it is not only required that each yarn has a uniform thickness, but also that the difference in yarn thickness between each path must be strictly controlled. Otherwise, it will cause defects such as horizontal stripes and shadows on the fabric surface, reducing the quality of the fabric.
4. Yarn should have good moisture absorption
The ability of yarn to absorb moisture in the air is called hygroscopicity. The moisture absorption capacity of various fibers varies greatly, and the amount of moisture absorption varies with the temperature and humidity of the air. The yarn used for knitting production should have a certain degree of moisture absorption. Under the same relative humidity conditions, yarn with good moisture absorption not only has good conductivity, but also benefits the stability of yarn twist back and the improvement of elongation, thus making the yarn have good weaving performance.
5. Yarn should have a certain degree of twist
Generally speaking, the twist of knitted yarn is lower than that of woven yarn. If the twist is too large, the softness of the yarn is poor, and it is not easy to be bent or twisted during weaving. It is also easy to produce knots, causing weaving defects and damaging the knitting needles; In addition, yarns with excessive twist can affect the elasticity of knitted fabrics and cause the coils to tilt. But the twist of knitted yarn should not be too low, otherwise it will affect its strength, increase the breakage during weaving, and the yarn will become loose, making the fabric prone to pilling and reducing its wearability. Therefore, selecting the correct twist is an important way to choose yarn reasonably. Knitted fabrics have different uses and twist requirements.
Sweat fabric should be smooth, tight, with a smooth surface and clear patterns. The twist of the yarn should be larger, which can be close to the standard of warp yarn for machine weaving with the same linear density. The twist of the yarn used for outerwear should be increased to enhance firmness and improve pilling and pilling. Cotton wool fabric and elastic fabric require a soft and elastic hand feel, and the twist of the yarn should be slightly lower. Generally, trademark yarns use the lower twist deviation of weft yarns with the same linear density for machine weaving. The yarn used for plush knitted fabrics requires less twist to facilitate flanging and ensure even pile thickness. In addition, the size of twist also varies with the yarn density.
6. Yarn should have good smoothness and a small coefficient of friction
Knitting yarn should be as free of impurities and oil stains as possible, and should be very smooth. Unsmooth yarn can cause severe friction and damage to the machinery, and there are many flying flowers in the workshop, which not only affects the health of workers, but also affects the productivity of knitting machines and the quality of fabrics.
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