What factors affect the color fastness of reactive dye printing?

The reason for the bad color fastness of reactive dyes: the fixation rate of reactive Du dyes is low, and the fixation rate of domestic K reactive dyes is mostly 60% ~ 70%. Therefore, the unfixed dyes (including hydrolytic dyes and dyes that do not react with fibers) on fabrics must be removed by adequate washing and soaping. However, there is intermolecular force between the unfixed dyes and cotton fiber, and some of them remain on the fabric after soaping. At the same time, the covalent bond between some reactive dyes and cotton fiber is easily broken due to the influence of external conditions. These are the important factors that cause poor color fastness. If the barium value of semi-finished products is low, the adsorption capacity of cotton fiber to dyes is small, the fixation rate of reactive dyes will be reduced, and the color fastness will be poor.

1 color fastness to dry rubbing

When testing the color fastness to dry rubbing, the friction force between the dry white cotton fine cloth and the figured cloth is far greater than the intermolecular force between the unfixed dye and the cotton fiber. Therefore, these dyes are easy to fall off in the process of rubbing, resulting in poor color fastness to dry rubbing.

2 color fastness to wet rubbing

When testing the color fastness to wet rubbing, the friction between the dye and the wet white cotton cloth will cause the dye to fall off, and the unfixed dye contains hydrophilic groups, which is very easy to transfer from the cotton fiber to the wet white cotton cloth, resulting in poor color fastness to wet rubbing.

3 color fastness to perspiration

Under the action of perspiration, some reactive dyes are prone to break bonds and hydrolyze, resulting in the increase of hydrolyzed dyes. Moreover, the unfixed dyes are easy to diffuse and transfer to the white cotton fabric, resulting in the fading of Perspiration resistance and the deterioration of staining fastness.

4 color shift fastness

The color fastness was determined according to the requirements of Japanese customers. The capillary test method was used to sew 10 cm × 2.5 cm white cotton cloth and 3 cm × 2.5 cm fancy cloth to be tested together, hang the white cotton cloth, then soak it in 0.05% Pingjia solution for 30 min, and dry it naturally to evaluate the penetration of color spots on the white cotton cloth. Due to the surface active agent Pingjia has the function of color stripping and diffusion, the unsettled dyes migrate to the white cotton cloth with the solution, resulting in the poor color transfer fastness [2].