How many forms of spandex elastic fiber yarn are there?
Spandex elastic fiber is mixed with other fibers and spun into elastic yarn. There are currently three forms of yarn: spandex core-spun yarn, Spandex twisted yarn and spandex covered yarn. The three forms of yarn are essentially different in processing principles and structural properties. Therefore, their uses and weaving properties also vary greatly. The structural diagram of the three types of yarns is shown in the figure.
What is the origin of spandex fiber and what are its main properties?
Spandex fiber is a kind of elastic fiber. Elastic fiber is collectively called Spandex abroad.
(Spandex), the product name of our country is spandex. In fact, spandex is only a major category of elastic fiber. Spandex fiber (Polyurethane
Fibre), referred to as PU fiber, has two varieties. One is a copolymer made of aromatic diisocyanate and polyester segments containing hydroxyl groups, referred to as polyester spandex. The other variety is made of aromatic diisocyanate and polyether containing hydroxyl groups. Segment-embedded copolymer, referred to as polyether spandex. The representative trade name of polyester spandex is Vyrent, and the representative trade name of polyether spandex is Lyera.
(Lecla).
The main properties of spandex fiber are: usually an elongation of more than 500% to 700%, and good elastic recovery performance. It retracts 97% at 200% elongation and over 99% at 50% elongation.
The relative density difference of various spandex is small, generally 1.20~1.25, and the breaking strength is 4.41~8.82cN/tex (0.5~1.0g/denier). The strength of polyester spandex is lower. Polyether spandex has higher strength. The moisture absorption rate is generally 0.3%-1.2%. The moisture absorption rate of multifilament is slightly higher than that of monofilament. The heat resistance is generally between 95 and 150°C. Short-term storage will not damage the fiber. The safe ironing temperature is below 150°C.
Fiber burns slowly and forms a gelatinous residue after burning. It has excellent dyeing performance, can be dyed in a variety of colors, and has strong affinity for dyes. It has good acid and alkali resistance, can be bleached, and does not become moldy.
Spandex dyeing
Spandex can be dispersed Dyes with dyes and acid dyes, but the fastness of these two dyes is too poor, and experiments have shown that nylon reactive dyes (dyed with nylon elastic fabric) and dispersed cationic dyes (dyed with CDP elastic fabric) basically do not stain spandex. , does this mean that these two dyes are not suitable for spandex dyeing? In fact, it is not the case. Under the premise of using suitable additives as a medium, reactive dyes for nylon can be used to dye spandex, and the fastness and depth are relatively good.
There are very few pure spandex fabrics on the market, so spandex dyeing is relatively unfamiliar. Pure spandex fabrics can be used together with low-elastic fabrics or non-elastic fabrics to increase the elasticity and resilience of the fabric. And when the elastic fabric is stretched or pressed, if the color of the spandex is inconsistent with the filament, there will be a problem of color leakage of the spandex, which requires dyeing the spandex.
For dyeing light colors of spandex
It can be dyed with acid dyes or disperse dyes under acidic bath conditions. Under the same dye dosage conditions, disperse dyes have various effects on spandex. The fastness is better than acid dyes, but different disperse dyes have different fastnesses to spandex. Generally, disperse dyes can be used for dyeing when the dye dosage is less than 0.5%.
Spandex is a high elastic fiber. Considering that dyeing for a long time under high temperature conditions will cause the spandex to lose elasticity, it is usually dyed below 100℃, and spandex is not resistant to alkali. Furthermore, disperse dyes and acid dyes are suitable When dyeing under acidic conditions, generally spandex is dyed under acidic bath conditions, and the pH is around 5.
Various dyes can be used to dye spandex using suitable additives as media. This type of additives is called spandex colorant or spandex colorant on the market. It is mainly used for reactive dyes for nylon, Spandex dyed with acid dyes is generally zwitterionic in nature.
The working principle is roughly as follows:
Under acidic conditions, the amide bonds and other groups in spandex are ionized and become positively charged, and the spandex coloring agent reacts with them Reaction, the color fixing agent is fixed on the spandex. Since the spandex coloring agent contains amino cations, the dye and the spandex coloring agent can also occur.minutes, gradually raise the temperature to 40°C, add bleaching water three times, add 1/5 of the total amount of bleaching water for the first time, 2/5 of the total amount of bleaching water for the second time, and add the remaining 2/5 of the bleaching water for the last time. According to the actual bleaching process Time operations.
2. After bleaching, drain water and add water at the same time. The water temperature will gradually drop. The reason for this is to prevent the spandex from being brittle and elastic due to a sharp drop in temperature.
3
Soft
Due to the different formulations of softeners and silicone oils from various additive manufacturers, some softeners and silicone oils can damage the elasticity of spandex. This is mainly due to the small amount of solvent in their components, which affects the elasticity of spandex. influential. Some silicone oils and softeners basically do not contain this solvent and have no effect on the elasticity of spandex. Choose the appropriate silicone oil for softening.
4
Solvent
Since the spandex weaving process contains silicone-based oils, the oils need to be removed during the dyeing and finishing process. Many scouring agents contain solvents, which have a great impact on the elasticity of spandex.
5
Physical cutting
Because the characteristic of denim is nostalgia, many of them need to be physically damaged and cut. The damage exerts uneven force on the spandex elastic yarn, resulting in blistering of the spandex and the exposed yarn. The thread can also break easily, causing loss of bullets.
6
Drying temperature
Generally, the drying temperature of denim fabrics containing spandex elastic yarn is lower than 60°C, so excessive temperature will cause great damage to the spandex elasticity.
