How To Improve The Color Fastness Of Reactive Dyes

The main thing to talk about here is Cotton fabric Color fastness of! Let's talk about the wear fastness of dark colors, such as dark red and black!

In most cases, the reason for the low wet rubbing fastness of cotton fabric is not the shedding of dyes, but the shedding of raw fibers of cotton after dark dyeing, which reduces the appearance fastness. Due to the high friction resistance of cotton in the wet state, the raw fiber is attached to the stained white cloth after falling off. In the dry state, cotton has less friction resistance and less shedding of raw fiber, so it is unlikely to have problems in dry friction fastness.

When confirming the wet rubbing fastness, use reactive black dye to dye and soap cotton fiber, and then use organic solvent (dimethylformamide) for extraction test. Even the dyed fabric with good dye fixation can only reach Grade 2-3 in the wet rubbing fastness test. Therefore, poor dyeing is not the direct cause of poor wet rubbing fastness.

However, if the dyes attached to the fabric surface are not thoroughly soaped, the wet rubbing fastness may sometimes be lower than Grade 2. The dyed material must be soaped thoroughly during dark dyeing. According to the test results dyeing The limit of its dark wet rubbing fastness is 2~3 grades, but generally it is difficult to reach 3 grades.

As mentioned above, the shedding of raw fiber will have a certain impact on the yarn shape, fabric texture and other fiber surface states. Even if the same dye and depth are used for dyeing, it will also produce a difference of about half a grade. Reducing the friction coefficient of fiber surface has a certain effect on improving the wet rubbing fastness. It is also very effective to use waterproof finishing agents such as silicon. If these methods are used, it may change the style or functionality of the fabric, so it is not suitable for any situation.

In addition, the wet friction resistance of polyester fabric is smaller than that of dry friction resistance. On the contrary, it has high wet friction fastness and low dry friction fastness.

Dyeing cellulose fiber with dyes forms chemical combination with fiber in the form of covalent bond. Therefore, theoretically, the covalent bond between dyes and fibers can endow dyes with excellent dyeing fastness. However, in fact, its dyes often fade, discolor or stain during testing, use, washing, and even storage. In particular, the wet rubbing fastness and soaping fastness when dyeing dark colors, and the fastness to sunlight and chlorine bleaching when dyeing light colors are unsatisfactory.

There are two main reasons for its poor color fastness: one is the problem of the dye itself; Second dyeing Problems.

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