Analysis of color fastness to soaping of textiles

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Color fastness of textiles to soaping and dyeing

Comparison of test methods for color fastness to soaping

Color fastness to soaping is one of the more common color fastness assessment items. Color fastness to soaping refers to the degree of fading of colored fabrics after soaping under specified conditions. It includes two evaluation contents: original fading and white cloth staining. Original fading refers to the fading of colored fabrics before and after soaping; white cloth staining refers to the situation where white cloth and colored fabrics are sewn together in a certain way, and after soaping, the white cloth is stained due to the fading of the colored fabrics. The degree of fading or staining should be tested under the specified light source and rated with a standard gray card. The results are divided into 5 levels, with level 5 being better and level 1 being poor.

The relationship between dye structure, dyeing and post-treatment technology and soaping color fastness

In daily tests, a considerable number of textiles, including cotton, wool, polyester, nylon and their blended fabrics, as well as elastic fabrics containing spandex, stained nylon and acetate fiber linings within 3 level or below. Although the dyes and printing and dyeing processes used in different fiber materials are different, the problems that arise are quite similar. This is mainly related to the floating color on the cloth surface and the transfer of some colored fiber particles, and is therefore also related to the type of dye used, the dyeing process and the post-processing process.

The color fastness of reactive dye dyeing products to soaping depends on the unfixed dye

Take reactive dyes as an example. Theoretically, since dyes form covalent bonds with fibers, water washing cannot easily cause dye desorption, fading and bleeding. Therefore, reactive dye dyeing products The color fastness to soaping depends on the amount of unfixed dye (hydrolyzed dye and a small amount of unreacted dye). If the hydrolyzed dye cannot be completely removed by soaping, the color will continue to fade after subsequent washing. Soaping fastness is also related to the bonding stability of bonded dyes, and bond-broken dyes will also fade when washed. Therefore, the most important factors affecting the color fastness to soaping are the dye structure and properties, followed by dyeing and post-dye treatment processes. Reactive dyes have a high fixation rate or a slow hydrolysis rate, resulting in a small amount of hydrolyzed dye and a small amount of dye that needs to be removed by washing. Unfixed dyes and hydrolyzed dyes have low directness, good water solubility, are not easy to stain, and are easy to wash off. However, if the dye concentration is high and the amount of residual dye is large, it is difficult to wash off.

The functional fabrics produced by the city’s textiles have been tested and their color fastness to soaping can reach level 4-5, which meets the requirements of international standards.

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