Reasons affecting the color fastness of reactive dyes
Tag:
Reactive dyes fabric dyeing fabrics textiles
Reactive dyes dye cellulose fibers to form chemical bonds with the fibers in the form of covalent bonds. Therefore, theoretically, the covalent bond between the dye and the fiber can give the dyed goods excellent dye fastness. But in fact, dyes often fade, change color or become stained during testing, use, washing, and even storage. In particular, the wet rubbing fastness and soaping fastness when dyeing dark colors, and the sun fastness and chlorine bleaching fastness when dyeing light colors are all unsatisfactory. There are two main reasons for the poor dye fastness: one is the problem of the dye itself; the other is the problem of the dyeing process.
1. Dye issues
Reactive dyes dye cellulose fibers. The dye is chemically bonded to the fiber in the form of covalent bonds, but when the dye is affected by moisture, heat, light, acid, alkali and oxidizing agents, some parts of its parent structure will change. For example, the decomposition of azo groups, oxidation of amino groups, detachment of complex metal ions, or hydrolysis and cleavage of covalent bonds of dye fibers, etc. will result in discoloration and lower fastness of some dyed goods. Another example is that the covalent bonds established between reactive dyes and cellulose macromolecules will hydrolyze and break under certain conditions, turning into hydrolyzed dyes and falling off, resulting in poor wet fastness and light fastness of the dye.
2. Problems with dyeing process
During the use of reactive dyes, dyeing Whether the method is correct or not directly affects the dye fastness of dyed materials. For example: improper chemical materials, hydrolysis of dyes, too hard water, too many calcium and magnesium ions, causing dye aggregation and precipitation; improper fixation conditions, low fixation rate; poor washing and soaping after dyeing, and failure to remove unfixed dyes Net; the finished product contains acids, alkalis, increased chain breakage due to hydrolysis of the dye, etc., which will cause an increase in floating color. The so-called “floating dye” refers to the dye that is attached to the fiber but not bonded to the fiber. They include: dyes that are partially or fully hydrolyzed; dyes that are adsorbed on the fiber but do not participate in the reaction; dyes that have undergone an elimination reaction of the vinyl alum sulfate ester group and the sulfate ester group has fallen off, but are not bonded to the fiber. Since floating dyes have varying degrees of affinity for fibers, this creates difficulties in the washability of the dyes. Therefore, in actual use, it is impossible to completely remove the floating dye on the fiber by washing and soaping.
：Other
AAGHRTYJYITLUY
Disclaimer:
Disclaimer: Some of the texts, pictures, audios, and videos of some articles published on this site are from the Internet and do not represent the views of this site. The copyrights belong to the original authors. If you find that the information reproduced on this website infringes upon your rights, please contact us and we will change or delete it as soon as possible.
AA
