Why does the dyeing of cotton/rayon blends have different colors?

Pure cotton fiber has the advantages of good moisture absorption, alkali resistance and strong heat resistance, but the fabric finish, uniformity, feel and drape are not as good as rayon;

Rayon fiber has good dyeability, high brightness and color fastness, comfortable to wear, moisture absorption similar to cotton, but poor resilience and fatigue resistance, and is sensitive to temperature and tension.

The cotton/rayon blended fabric combines the advantages of the two. The fabrics made of muslin, vanillin, gabardine and other fabrics not only have the feel and comfort of rayon, but also have high moisture absorption and good dimensional stability. The characteristics of good gloss and high strength are well received by the public.

In the dyeing process, because rayon has a faster dyeing rate than cotton fiber, the color yield is higher, and it is easy to dye flowers, cotton/rayon blended fabrics are dyed with general reactive dyes, and the shade difference is large.

Because the dyeing is not synchronized, the flower is gray and white. This is not a color flower. And it can be solved by uneven dyeing and pre-treatment.

Need to dye cotton and rayon dyes with better synchronization.

Of course, another way of thinking is to reduce the dyeing speed of rayon;

In addition, there is information that the use of vat dyes for pad dyeing can also result in the problem of cotton/rayon dyeing homochromaticity; in "How to solve the problem of homochromaticity in cotton/rayon dyeing?" The following points are put forward in the article;

Due to the difference in structure and physical and chemical properties between cotton and rayon, the amount of color and shade after dyeing are different. The above two varieties were respectively subjected to continuous pad dyeing, cold pad batch dyeing and coil dyeing, and it was found that the continuous pad dyeing process had the best homochromaticity.

This is mainly because the dyeing time of cold pad batch dyeing and jig dyeing is longer, and the color difference between cotton and rayon is large. In the continuous pad dyeing process, the homochromaticity of the vat dyes is better than that of the reactive dyes. This is because the vat dyes are padding in a suspension, while the reactive dyes are covalently bonded to cotton and rayon.

The rayon fabric will swell and puff after being soaked. The increase in the diameter of the warp yarn will cause wrinkles on the cloth surface. Tentering treatment must be carried out before pad dyeing. After the bottoming machine is dried, the fabric width is reduced; after the reduction washing machine, the width is reduced again.

Therefore, it is necessary to stretch the frame before using the cleaning machine, otherwise wrinkles will occur. The criterion for judging is whether the widths of dry and wet cloths are similar. For the above two varieties, tentering is not required for blended cotton from cotton warp yarn, and tentering is required for blended cotton/rayon warp and weft.

In summary: cotton/rayon dyeing with vat dye pad dyeing can completely solve the problem of homochromaticity. However, because the vat dye chromatogram is not complete, the reactive dye dyeing process is sometimes required.

In short, in order to solve the dyeing of cotton/rayon blends, it is necessary to start from the selection of dyes, but also to make a fuss about the process of delaying dyeing and increasing leveling.