Detailed differentiation of cotton yarn

Raw cotton with high fiber strength, moderate maturity and good uniformity has more opportunities to remove neps and impurities on the yarn during the preparation and weaving process. , and also needs to go through the sizing process, so the requirements for the color and impurity content of the raw cotton are low, the weft yarn is not sizing, the preparation process is simple, there are few opportunities to remove impurities, and the weft yarn is mostly exposed on the surface of the fabric, so the weft yarn affects the color and appearance of the fabric, Factors such as hand feel have a greater impact, but the weft yarn does not require high strength, so you can choose raw cotton with good color, less impurities, thicker and shorter, and slightly lower tension.

3. Yarn for knitting

Knitted products are made of single or several yarns knitted by a knitting machine. They are suitable for yarn breakage, defects, strength and dyeing effect. The requirements are higher. Knitted yarn is generally used to make underwear, which requires softness and comfort. Therefore, the twist of the yarn is small, and the evenness of the knitted yarn is important. The requirements are very high, and yarns with uneven thickness are particularly obvious on fabrics. Therefore, when blending cotton, all aspects of yarn strength, evenness, defects, and number of broken ends must be taken into consideration. Therefore, fiber slenderness and uniformity should be selected. Good, raw cotton with normal maturity, low short staple rate, and few defects. For knitting yarn for fleece fabrics, raw cotton with good maturity, good elasticity, and short length should be selected.

4. Yarn for dyeing

Generally, cotton fabrics need to be finished and dyed. The color absorption capacity of the fabric has a great relationship with the performance of the fiber. Light-colored cloth has a negative impact on raw cotton. The requirements are not high, but raw cotton with a low maturity coefficient and large differences cannot be used, otherwise it will cause uneven fiber mixing, and spots or stripes will appear on the fabric after dyeing. Therefore, light-colored fabrics are required to use less impurities and better color. of raw cotton. Dark cloth versus fiberThe requirements for color absorption capacity are high, and raw cotton with good maturity is required. The requirements for raw cotton for printed fabrics can be lowered, because after printing, some yarn defects and rungs on the cotton fabric can be covered. For yarn-dyed yarns, single-color fabrics are required. Yarn, one-color cloth, also known as Mitong cloth, is made of dyed yarn to weave high-end decorative or clothing fabrics. Because the yarn has to go through multiple processes during the dyeing process, the yarn is required to be free of hairiness, yarn defects, and joints. Currently, there are very few yarns in China that can reach high-end single-color fabrics.

5. Special yarns

There are many types of special yarns, such as curtain yarns for tires, high-end sewing threads, decorative fabric yarns, handkerchief yarns, etc. , it is required to select specifically according to the quality requirements when matching cotton, and the phenomenon of universal cotton matching must not be caused. In the yarn purchase contract, in addition to requiring the yarn mill to order yarn according to the purpose of the yarn, many orders also require specific quality and technical indicators of the yarn, such as evenness CV value, nep defects in the finished yarn, etc., as well as the quality of the cotton yarn. , in addition to production management, process conditions, mechanical status, operating level, etc., it is also related to all The quality of raw cotton has a lot to do with its reasonable use. Therefore, we must master the different requirements of yarn quality on raw cotton and the relationship between them, and give full play to the technical performance of the raw materials. When the cost of cotton distribution is relatively low, Under this situation, improving yarn quality, stabilizing production and reducing production costs play an important role.

Spandex’s scientific name is polyurethane fiber, also called polyurethane elastic fiber, commonly known as spandex filament. It was first successfully developed by the German company Bayer in 1937, but there was no industrial production at the beginning. It was not until 1985 that the American DuPont Company developed spandex yarn again (currently more popular, such as DuPont’s DuPont Spandex) and mass-produced it. Spandex is a special fiber with extremely high elasticity and is currently the most elastic synthetic fiber known in the world.

1. Appearance

The appearance of spandex yarn can be divided into Z direction and S direction, which is the twist direction of spandex yarn.

2. Elasticity

Spandex yarn has great elasticity and can be stretched to 4 to 7 times the length of the original yarn, and some can reach more than 8 times. The recovery rate is almost 100% under the original 2 times stretch. When the elongation is 400 to 500%, its rebound rate is 97 to 99%, which is incomparable to other fibers. In the molecular structure diagram of spandex fiber, the greater the molecular weight of the soft chain molecular segment, the stronger the resilience of the fiber. Polyether spandex has higher elasticity and resilience than polyester spandex; chemically cross-linked spandex has a higher resilience Good physical cross-linking…

3. Strength

The strength of spandex yarn is about 0.35-0.88 in wet state and 0.44-0.88 CN/dtex in dry state, which is 3-5 times that of rubber yarn. The effective strength can reach 5.28 CN/dtex.

4. Production process

Spandex covered yarn is divided into single package, double package and other covering forms. Among them, nylon spandex and polyester spandex are mainly single-packed (Haining City, Zhejiang) air-coated yarn. The outer fiber filament and spandex yarn are simultaneously drawn through a certain type of nozzle, and the high-compressed air is sprayed regularly to form a rhythm. Sexual network dots of yarn. The fabric feels soft and smooth; the mechanical covering yarn continuously rotates and wraps the outer fiber filament around the core spandex that is drawn at a constant speed. It is twisted and has a twist. The smooth and crisp fabric style is its main feature .

Empty machine-wrapped yarns have their own advantages and disadvantages when weaved in downstream weaving factories. Empty bales generally need to be sized when being warped on an air-jet loom, otherwise the fabric is prone to fluffing and broken wires, etc. However, it can be used directly after beating up. Considering the cost alone, the production capacity of empty bales is much higher than that of machine bales, making the price lower than that of machine bales, which facilitates the reduction of costs for downstream weaving mills. Although the core yarn is not exposed in machine bags, it is generally not prone to quality problems during spinning and weaving except for uneven twist. However, the output is low, and the price is therefore more than RMB5000/T higher than empty bags of the same specification. The price of fine denier covered yarn It is even higher than RMB10,000/T for empty packages of the same specifications, thus greatly increasing the cost of using machine packages.

In the spinning process, the pre-draft ratio of spandex is an important process parameter. It affects the elasticity of the covered yarn and fabric, as well as the strong elongation and uniformity of the covered yarn. strength and creep properties. The pre-draft multiple of spandex is too small, which cannot give full play to the advantages of elastic fabric. When the draft is too high, it is difficult to spin, and it is easy to cause wire breakage, and the product quality will decrease; in addition, the percentage of spandex fiber also affects The elasticity of the covered yarn is high, and the elasticity is good. When the spandex yarn specifications are certain, increasing the draft ratio will reduce the percentage of spandex yarn, that is, the pre-draft multiple of spandex is inversely proportional to the percentage of spandex in the finished yarn.

The strength and elongation of the covered yarn increases with the increase of the spandex pre-drafting multiple. After the spandex is stretched to a certain value, the retractability of the spandex yarn causes the outer fiber to be in a curled state, and the spandex core yarn Straightened; increase the pre-drafting ratio appropriately, reduce the percentage of spandex, and curl the outer fiber to a large extent. However, when the draft is too large and the deformation amplitude of the spandex yarn approaches the critical value of deformation, the strength and elongation of the covered yarn will decrease, but it will help the evenness of the covered yarn.

The phenomenon of deformation changing with time under the action of constant drafting force is called creep. The covered yarn has good creep resistance when the spandex yarn is pre-drafted 3.5 times.

The twist of the machine package affects the quality, elongation and evenness of the yarn. Increasing the twist can increase the cohesion between the covering fiber and the spandex yarn, thereby increasing the strength of the covering yarn. The elongation of the machine bag is mainly determined by the performance of the spandex core yarn. If the twist is too large and the outer fiber is wrapped too tightly, the elastic effect of the spandex yarn cannot be fully exerted, causing the elongation to decrease. As twist increases, evenness improves. The twist is too small and the outer fibers are loose. During the spinning process, the fibers will move slightly along the axis of the yarn due to friction and other reasons. Therefore,The dryness has deteriorated.

The presence of spandex yarn in the machine bag will weaken the cohesion between the outer fiber filaments. The twist is too low and the outer fiber will be loose, which will affect the covering effect and lead to core exposure. Therefore, the twist should be adjusted during mechanical wrapping. On the high side. But if the twist is too high, the fabric will feel hard and have poor drape. Generally, the twist needs to be adjusted as the denier of the yarn changes. For example, for N40D+20D machine packages, the twist is 600 twists, while for N70D+40D or T150D+40D machine packages, the twist can be controlled at around 480. Some small In order to consider delivery time and reduce production costs, spinning mills will reduce twist or increase equipment speed to increase output, which is not conducive to the quality of wrapped yarn.

1. Pure spun yarn

Pure spun yarn is composed of the same fiber, such as pure cotton yarn, acrylic yarn, polyester yarn, nylon yarn, viscose yarn Glue yarn, etc. 2. Blended yarn

Blended or twisted yarn is a yarn composed of two or more fibers, such as: blending of cotton yarn and polyester yarn; blending of cotton yarn and acrylic yarn; spinning of wool yarn and polyester yarn; rabbit hair Yarn nitrile blended yarn; polyester/viscose/nitrile blended yarn, silk yarn and cotton yarn twisted yarn, etc. At the same time, there are yarns composed of two or more filament yarns called blended yarns. Common blended yarns for socks include polyester-cotton, cotton-polyester, wool-polyester, wool-polyester, silk-viscose, etc.