1. Test method for color fastness to soaping
Soaping color fastness is one of the most common color fastness assessment items. Soaping color fastness refers to the degree of fading of colored fabrics after soaping under specified conditions, which includes two evaluation contents: original fading and white cloth staining. As-is fading refers to the fading of colored fabrics before and after soaping; white cloth staining refers to the situation that white cloth and colored fabrics are sewn and stacked together in a certain way, and after soaping, the white cloth is stained due to fading of colored fabrics. The degree of fading or staining should be tested under the specified light source and graded on a standard gray card. The results are divided into 5 grades, with 5 being the best and 1 being the worst.
2. Relationship between dye structure, dyeing and post-treatment process and color fastness to soaping
In daily tests, a considerable number of textiles, including cotton, wool, polyester, nylon and their blended fabrics, as well as spandex-containing elastic fabrics, stained nylon and acetate fiber linings at grade 3 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 of the cloth surface and the transfer of some colored nits, so it is also related to the type of dye used, the dyeing process and the post-treatment process.
3. Soaping fastness is also closely related to the dyeing process
In addition, soaping fastness is also closely related to the dyeing process. The dye adsorption and diffusion are sufficient, the fixation rate is high, the residual dye and hydrolyzed dye are less, and it is easy to wash off. The dyeing process is reasonable, the covalent bond between the dye and the fiber is not easy to break during dyeing and post-treatment, and the color fastness to soaping is good.