Polyester yarn

Hot sale dope dyed polyester poy 100% polyester yarn

After finishing the dyed fabric, why does the color light change? How to deal with it?

1. Causes

After dyeing and finishing, the color light of the fabric will change to some extent. This is a common phenomenon in dyeing. After analysis, the following factors are closely related to the fluctuation of color light.

① After many dyes are dyed, they are not stable but metastable (vat dyes are the most prominent). After the wet and heat treatment of the rear passage, the following changes may occur:

a. The dye molecules in the highly dispersed state in the fiber will further aggregate, which will change the crystalline state of the dye to some extent.

b. The dye molecules in the fiber will change from the parallel state of the fiber molecular chain to the vertical state, which will change the orientation of the dye.

c. The dyes with the tendency of molecular isomerization (CIS trans) will change their configuration.

The change of crystal, orientation and configuration of the dye dyed in the fiber will inevitably lead to the change of the absorbance of the dye, which will cause the fluctuation of color and light.

② Common finishing agents (softener, waterproof agent, antibacterial agent, UV resistant agent, etc.) will cause the following problems in the process of wet and heat treatment:

a. There are some complex chemical reactions between cationic auxiliaries and cationic dyes.

b. The auxiliary film on the fiber will turn yellow to some extent.

C: The pH (mainly acidity) of the finishing solution will cause the color light of the dye to change.

d. After finishing agent can promote disperse dyes to produce different degree of "heat transfer" and "heat sublimation" at high temperature. The complex relationship between finishing agent and dyestuff will inevitably affect the color light of dyeing.

③ After finishing, the color light of dyed cloth may change during the placing process. The main influencing factors are as follows:

a. There are different "three sensitivities" (humidity sensitivity, heat sensitivity and photosensitivity) in common dyes. That is to say, the dyeing light will vary with the moisture content, temperature and light intensity of the fiber. Therefore, once the moisture content, temperature and light of the fabric change, its color light will be different.

b. The residual minerals and heavy metal compounds (mainly from water and finishing agent) in the fabric will slowly have complex chemical interaction with the dye during the placing process, which will cause the change of color light.

c. In the process of placing the color cloth, the acid, alkaline gas or oxidizing and reducing gas in the surrounding environment will also lead to the decline of the stability of the dye, and then the color and light will change.

2. The countermeasures are as follows

① After dyeing, it must be fully cleaned (saponified). There are two reasons: one is that full washing (soaping) can promote the dye in the fiber to achieve stable state in terms of crystallization, orientation, configuration, etc.; the other is that floating color (including staining) dye is more sensitive to humidity, heat, light, acid, alkali, chemicals, and more likely to cause changes in color and light. Fully washing (saponification) the floating color and all kinds of dyeing chemicals can be removed as much as possible, which will undoubtedly improve the stability of the color light.

② The dye should be optimized. To choose "three sensitive" phenomenon is not obvious, color light by finishing agent and acid, alkali effect is small. Disperse dyes should have good fastness to "heat transfer" and "heat sublimation".

③ The finishing agent should be used preferentially. To choose the yellowing of small, light impact on the color. Therefore, it is necessary to do pioneering experiments in advance.

④ The workshop should strengthen ventilation and improve the air cleanliness. Moreover, the cloth box should be covered and the finished product should be timely.

The above comprehensive measures can obviously improve the color and light stability of dyed fabrics.