Spandex yarn has formed different yarn styles due to different processing principles and technological processes, thus enriching the application fields of spandex fiber. This paper introduces the processing principle of core spun yarn, wrapped yarn and twisted yarn.

1.Core spun yarn of spandex yarn

Core spun yarn of spandex yarn which is wrapped with one or more non elastic staple fibers. Ring spinning, rotor spinning, electrostatic spinning and other spinning methods can be used, among which ring spinning is the most widely used. Domestic spandex is usually equipped with a set of active drafting and feeding mechanism on the ordinary ring spinning frame. The production process is to feed and combine the drawn staple fibers and spandex from the front jaw of the spinning frame at the same time, pass through the yarn guide hook, and then make the spandex core spun yarn through the twisting and winding of the steel ring and the steel ring. The content of spandex in the core spun yarn should not be too high, otherwise the cohesion between the coated fibers will be destroyed, resulting in the decrease of yarn strength.

This yarn has the advantages of low spinning cost, large yarn count range, wide wrapped fibers (cotton, wool, viscose, etc.) and flexibility. However, it has high requirements for the operation level of the equipment. It should try to reduce the number of starts and stops, reduce the breakage rate and reduce the phenomenon of coreless or eccentric cores.

2.Covered yarnof spandex yarn

Covered yarn of spandex yarn refers to the elastic yarn made by uniformly wrapping the wrapped short fiber or filament yarn with the pre stretched spandex as the core wire according to the spiral method. It is the most commonly used variety in spandex processing. The coated yarn is divided into single coating and double coating. Single coating refers to that the outer fiber is wrapped around the spandex wire in the direction of single helix, and double coating refers to that on the basis of single coating, it is wrapped with a layer of helix.

The single coated yarn is easy to expose the core yarn in a tense state, resulting in poor evenness and even whitening after dyeing, so it is not suitable for dark products. In order to avoid this disadvantage, spandex can be double coated.

3.Ply yarn of spandex yarn

Ply yarn of spandex yarn is made by twisting one or more strands of pre stretched spandex and other non elastic fibers. Twisting yarn is usually processed by a modified twisting machine. The linear speed of the output roller of the twisting machine exceeds that of the active feeding roller of the spandex, so the spandex is drawn in the process of unwinding the active feeding. The spandex in the drawing is combined with two or more single yarns through the worm yarn guide, and twisted to become the spandex twisting yarn.

The advantages of Ply yarn are: (1) It can be matched with various yarns or filaments (2) It is suitable for small batch and multi variety production. However, this kind of yarn is easy to be exposed under tension, resulting in color difference after dyeing, so it is not suitable for dark products.

Spandex yarn is a kind of high elastic fiber with excellent properties, such as large elongation and high elastic recovery rate. With the progress of chemical industry, chemical fiber and textile technology, the application field of spandex fiber will be broader.