Spandex is a highly elastic fiber, with a small amount of spandex fiber and other to form a certain scale. The fiber is mixed, and the woven elastic fabric can be used for tight underwear, shirts, sportswear, denim, casual wear and other clothing, which is favored by consumers.
There are two types of soft segments in the spandex fiber chain structure: polyester and polyether, which are divided into polyester spandex and polyether spandex. Generally, polyether spandex has a lower glass transition temperature and better elasticity than polyester spandex.
Spandex can be directly used in the form of bare silk to weave elastic fabrics, or bare silk can be processed into a certain form of elastic yarn and then used to weave elastic fabrics. Among them, there are three most widespread forms: spandex core spun yarn, spandex twisted thread and spandex covered yarn.
The processing principles of the three elastic yarns are different, which determines that their fiber structures are quite different, which is the fundamental factor affecting the performance of the yarn. Spandex corespun yarn can be spun by ring spinning, vortex spinning, electrospinning and other methods, and the most widely used is ring spinning. Spandex twisting thread, also known as stranded thread, is processed after modification by using a twisting machine. Spandex covered yarn is processed on special equipment with hollow core spindles, which are covered in a single layer when one core spindle is used and double-layer when used in two.
Spandex corespun yarn structure characteristics and performance analysis
Spandex core-spun yarn is a yarn spun with spandex yarn as the core and one or several non-elastic staple fibers. The core yarn of the core yarn is surrounded by the outer fibers, which are tightly bonded and have the same twist as the outer fibers.
It has three significant characteristics: first, it has the same feel and appearance as the outer fibers (cotton, wool, polyester, cotton, etc.), and the outer sheath composed of natural fibers has good hygroscopicity; Second, the elasticity is good; Third, the elastic percentage can be controlled below 20%.
Compared with other stretch yarns, spandex corespun yarn has a significant feature that the core yarn is not exposed when the yarn is tense and stretched. Therefore, the dyeing effect is good, and it is advisable to make products of various colors, including dark colors.
Compared to other types of stretch yarns, corespun yarns have comparatively lower strength. Under normal circumstances, the strength of a single yarn is only equivalent to 80%~90% of the same specification when the outer fiber is yarn alone. The first break of the core spun yarn is the outer fiber, and the strength formed by the outer fiber is the strength of the core spun yarn. Spandex yarn is a low-strength and high-elongation filament, which does not help the strength of the yarn in the core-spun yarn, but destroys the holding force between the fibers. Therefore, the higher the spandex content, the lower the strength of the corespun yarn.
Structural characteristics and performance analysis of spandex twisted thread
Spandex twisting thread is made of stretching elastic spandex yarn edge drawing edge and two inelastic yarns combined and twisted. If this yarn is unwound, while easing the tension, a lighter impact is added to the whole yarn, so that the yarns move to a stable state with each other, and as a result, the spandex yarn enters the yarn core, and the other inelastic yarn becomes the outer layer, so as to have the corresponding appearance and feel.
This kind of yarn spandex yarn has the same twist as the outer yarn, and in the tension state, the spandex yarn and other yarns have no obvious core sheath relationship, but the relationship between twisting each other. As a result, the spandex yarn is exposed in tension. Because the coloring performance of spandex yarn and other non-elastic yarns is inconsistent, it is easy to cause color difference, so it is not suitable for dark products.
Spandex elastic twisted yarn has the following advantages: first, spandex yarn can be matched with various yarns or filaments; Second, it is suitable for small batch and multi-variety production, and even a twisting machine can process several varieties and types at the same time; Third, the elasticity can be determined according to the use of the product; Fourth, it can be used with the same outer yarn as the fabric, so that the appearance of the product is consistent with the raw materials of the fabric, and the same hue can be achieved after dyeing.
The strength of the elastic twisted thread is the strength of the non-elastic yarn that is matched with the spandex yarn. Therefore, the strength is higher than that of spandex core-spun yarn of the same specification.
The degree of holding of spandex yarn and other non-elastic yarns in elastic twisted yarn is lower than that of spandex yarn and outer fiber in spandex core spun yarn, so the elasticity of twisted yarn is higher than that of core spun yarn.
Analysis of the structural characteristics and properties of spandex covered yarn
Covered yarn is also known as wrapped yarn, and one of the most obvious differences between covered yarn and other stretch yarns is the core yarn twistlessness. The core sheath relationship between spandex yarn and outer layer in covered yarn is obvious, but the degree of holding between core yarn and outer layer is significantly lower than that between core spun yarn and twisted yarn, so its elasticity is higher than that of the first two. The elongation can reach 200% (double yarn wrapping), and about 50% elasticity can be obtained in high-elastic fabrics.
The covered yarn has the phenomenon of exposing 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 spun yarn, and the strength of the covered yarn is the strength of the outer filament or yarn, so the strength is higher than that of the core spun yarn of the same specification.
From the processing process of the covered yarn, it can be seen that the covered yarn is loose winding, and the winding rate is generally 60%~95% according to the different uses. This is different from core spun yarn and twisted thread, which has a greater impact on the weaving process parameters.