Spandex is a highly elastic fiber, with a small amount of spandex fiber and other into a certain scale. Mixed use of fibers, woven elastic fabric can be used in tight underwear, shirts, sportswear, jeans, casual wear and other clothing, favored by consumers.
The soft chain segment of spandex fiber chain structure has two types of polyester and polyether, which are divided into polyester spandex and polyether spandex. Generally, polyether spandex has lower glass transition temperature and better elasticity than polyester spandex.
Spandex can be directly used to weave elastic fabrics in the form of bare silk, and can also be processed into a certain form of elastic yarn and then used to weave elastic fabrics. The most widely used are three types: spandex core-spun yarn, spandex twisted yarn and spandex covered yarn.
The processing principle of the three kinds of elastic yarns is different, which determines that the fiber structure is different, which is the fundamental factor affecting the performance of the yarn. Spandex core-spun yarn can be spun by ring spinning, eddy current spinning, electrostatic spinning and other methods, the most widely used is ring spinning. Spandex twisting is also called twine, which is processed by using a twisting machine after modification. The spandex covering yarn is processed on special equipment with empty core spindles, single coating when using one empty core spindles, double coating when using two spindles.
First, Structure characteristics and performance analysis of spandex core-spun yarn
Spandex core-spun yarn is a yarn made of spandex yarn with one or more non-elastic staple fibers. The core filament of the core-covered yarn is surrounded by the outer fiber, and the two are tightly combined. The core filament and the outer fiber have the same twist.
It has three significant characteristics: first, it has the same feel and appearance as the outsourcing fiber (cotton, wool, polyester, cotton, etc.), and the outer sheath composed of natural fibers has good hygroscopic property; Second, good elasticity; Third, the percentage of elasticity can be controlled below 20%.
Compared with other elastic yarns, spandex core-yarn has a remarkable feature that the yarn is not exposed under the state of tension tension. Therefore, the dyeing effect is good, and it is appropriate to do various colors of products, including dark colors.
Core-spun yarn has a relatively low strength compared to other types of elastic yarns. Under normal circumstances, the strength of a single yarn is only equivalent to 80% to 90% of the outsourced fiber of the same specification. The first thing to break is the outer fiber, and the strength formed by the outer fiber is the strength of the core yarn. Spandex is a filament of low strength and high elongation, which does not help the strength of the yarn in the core yarn, but destroys the adhesion between the fibers. Therefore, the higher the spandex content, the lower the strength of the core yarn.
Second, the structure characteristics and performance analysis of spandex twisting
Spandex twist is made by combining a stretch edge of elastic spandex and two inelastic yarns. If this yarn is decompressed, the tension is eased and the impact on the whole yarn is lighter, so that the yarns move to a stable state between each other, and the result is that the spandex wire enters the yarn core, and the other non-elastic yarns become the outsourcing layer, which has the corresponding appearance and feel.
This kind of yarn spandex yarn has the same twist with the outer yarn, and in the tensioning state, the spandex yarn has no obvious core sheath relationship with other yarns, but the relationship of twisting each other. So the yarn is exposed in the tensioned state of spandex. Because the coloring performance of spandex wire and other non-elastic yarn is inconsistent, it is easy to cause color difference, so it is not suitable to do dark products.
Spandex elastic twisting has the following advantages: First, spandex can be matched with various yarns or filaments; Second, it is suitable for small-batch multi-variety production, and even a twisting machine can process several varieties at the same time; Third, flexibility can be determined according to product use; Fourth, it can use the outsourcing layer yarn consistent with the fabric, so that the appearance of the product is consistent with the raw material of the fabric, and achieve the same hue after dyeing.
The strength of elastic twisting is the strength of non-elastic yarn matched with spandex. Therefore, the strength of the same specifications of spandex core-yarn is higher.
The degree of adhesion between spandex yarn and other non-elastic yarns is lower than that between spandex yarn and outer fiber in spandex core-spun yarn, so the elasticity of spandex yarn is higher than that of core-spun yarn.
Third, the structure characteristics and performance analysis of spandex covered yarn
Covered yarn, also known as wrapped yarn, one of the most obvious differences between covered yarn and other elastic yarns is that the core yarn has no twist. The core sheath relationship between the spandex and the outer layer is obvious, but the degree of adhesion between the core yarn and the outer layer is obviously lower than that of the core yarn and the twisted yarn, so the elasticity is higher than the first two. Elongation can be up to 200% (double wrapped yarn), and about 50% elasticity can be obtained in high-elastic fabrics.
The covered yarn is exposed to the core in the tensioned state, so it is not suitable for dark products. The feel of the covered yarn is harder than that of the core-covered yarn, and the strength of the covered yarn is the strength of the outer layer filament or yarn, so it is higher than that of the core-covered yarn of the same specification.
From the processing process of the covered yarn, it can be seen that the covered yarn is loosely wound, and the take-up rate is generally 60% ~ 95% according to the different uses. This is different from core-spun yarn and twisted yarn, which has great influence on weaving process parameters.
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