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The Rule of dyeing Spandex with Nylon Reactive Dye (Coloring agent for Spandex)

February 13,2023

Spandex fiber is a kind of elastic fiber, elastic fiber abroad collectively known as Spandex , in fact, spandex is only a major category of elastic fiber. Polyurethane Fibre has two varieties. One is made of aromatic diisocyanate and polyether chain segment embedded copolymer containing hydroxyl group, which is short for polyester spandex , and the other is made of aromatic diisocyanate and polyether chain segment embedded copolymer containing hydroxyl group, which is short for polyether spandex . The representative trade name of polyester spandex is Vyrent, while the representative trade name of polyether spandex is Lycra.

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The main properties of  spandex  fiber are: usually 500% ~ 700% of the elongation, elastic recovery performance is good. Retract 97% at 200% extension and more than 99% at 50% extension.
The relative density of various types of  spandex  varied little, generally ranging from 1.20 to 1.25, and the breaking strength was 4.41 to 8.82cN/tex(0.5 to 1.0g/denier). The strength of polyester type  spandex  was lower, while that of polyether type  spandex  was higher. The hygroscopic rate is generally 0.3%-1.2%, and the hygroscopic rate of compound wire is slightly higher than that of single wire. The heat resistance is generally kept at 95 ~ 150℃ for a short time without damaging the fiber, and the safe ironing temperature is below 150℃.
Fibers burn slowly and form a gelatinous residue after combustion. Excellent dyeing performance, can dye a variety of colors, strong affinity for dyes. Good acid and alkaline resistance, bleaching, no mildew.

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Law of dyeing

1. The general rule of fastness after dyeing  spandex  is: washing > perspiration (acid) > water immersion, and wet rubbing fastness is far better than dry rubbing fastness.
Analysis of the reason, after  spandex  coloring, dye or the combination of  spandex  coloring agent and dye will migrate in wet condition under the action of external pressure for a long time, and it is a slow process ( spandex  is a hydrophobic fiber, water molecules will not quickly enter the fiber, dye will not quickly migrate), so its washing fastness is good. Secondly, under the acidic condition of sweat stains, It is conducive to the ionization of amino group on the amide bond of  spandex  or  spandex  coloring agent, which can capture migrating dyes or the combination of  spandex  coloring agent and dyes, so acid sweat fastness is better than neutral water immersion color fastness. Under the action of friction, dry grinding will generate heat, resulting in thermal migration of dyes on the surface of  spandex , which does not occur under wet conditions.
2. Boiling soda ash after dyeing will reduce the fastness of  spandex  by about 0.5. This is because under alkaline conditions, the combination of  spandex  coloring agent and fiber and dye will be destroyed, thus decreasing the fastness. Second, after  spandex  dyeing with cationic color fixing agent, its fastness improvement is larger than anionic color fixing agent, cationic color fixing agent can react with the water-soluble group of dye (-SO3-), seal the water-soluble group, reduce the water solubility of the dye, and fixing agent on the surface of the fiber film, can isolate the dye, dry friction fastness will be improved accordingly.
3. Acid, disperse and nylon with reactive dye dyeing  spandex  sun fastness is worse than dyeing polyester or nylon filament. The main reason is that the crystallinity of  spandex  is low, and it is in a high elastic state at normal temperature. It is easier for air to enter into the fiber and change color under the action of sunlight. Moreover,  spandex  itself will turn yellow under the action of sunlight, which is also the reason for the low fastness to sun.
When cotton elastic cloth is dyed black,  spandex  will show white. Generally, a small amount of disperse or acidic black can be added to the dyeing bath to make it dyed with  spandex , but we should pay attention to the problem of fastness.
Secondly, for the black  spandex  coloring problem of polyester elastic force and nylon stretch cloth, a small amount of  spandex  coloring agent about 0.3% can be added into the dyeing bath when dyeing polyester stretch cloth, and nylon stretch cloth dyeing can be directly added into the dyeing bath dyeing  spandex  coloring agent, so that the  spandex  coloring problem can be basically solved. Other colors of  spandex  dew color problem, according to the above analogy.

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