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Analysis of the color fastness to soaping of textiles 2021.12.08

Comparison of test methods for soaping and dyeing fastness

Fastness to soaping dyeing is one of the more common assessment items of fastness to dyeing. Soaping dyeing fastness refers to the degree of color fading of colored fabrics after soaping under specified conditions, and it includes two evaluation contents of original color 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 fabric are stitched together in a certain way, after soaping, the white cloth is stained due to the fading of the colored fabric. The degree of fading or staining should be tested under the designated source and rated by a standard gray card. The results are divided into 5 levels, with 5 being good and 1 being bad.

The relationship between dye structure, coloring and post-treatment process and soaping dyeing fastness

In daily tests, a considerable part of fabrics, including cotton, wool, polyester, nylon and their blended chemical fiber fabrics, and spandex elastic fabrics, have staining of nylon and acetate fiber linings at level 3 or below . Although the dyes and printing and finishing processes used in different fiber materials are different, the problems that arise are quite similar. This is mainly related to the floating color of the cloth surface and the transfer of some colored fiber particles, so it is also related to the types of dyes used, the coloring process and the post-treatment process.

The fastness of soaping dyeing of reactive dyes is determined by the unfixed dyes

Taking reactive dyes as an example, theoretically speaking, because the dyes and fibers form a covalent bond, washing with water cannot easily cause dye desorption, fading and bleeding. Therefore, the fastness of soaping dyeing of reactive dyes is good or bad The decision is based on the number of unfixed dyes (hydrolyzed dyes and a small amount of unreacted dyes). If the hydrolyzed dye cannot be completely removed by soaping, the subsequent water washing will cause continuous color fading. The soaping fastness is also related to the bond stability of the bonding dyes, and the bond-breaking dyes will also wash off with water. Therefore, the most important factors affecting the fastness of soaping dyeing are the structure and performance of the dye, followed by the coloring and post-dyeing processes. Reactive dyes have a high fixation rate, or a slow hydrolysis rate, the amount of hydrolyzed dyes is small, and the amount of dyes that need to be cleaned and removed is also small. Unfixed dyes and hydrolyzed dyes are low in directness, have 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 not easy to wash and clean.

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