1. Test method for fastness to finish dyeing
The test of fastness to dyeing refers to the fabric sample and a set of standard samples are exposed to the artificial finish source under the specified conditions, and then the two are compared for color change to evaluate the fastness of dyeing.
2. Ways to improve the fastness to finish dyeing
The fading mechanism of the dye is particularly complicated, but the main reason is that the dye is intensified after the dye is absorbed, and a series of chemical reactions occur to destroy the structure, leading to discoloration and fading. The fastness of fabrics to finish dyeing mainly depends on the chemical structure of the dye, as well as its aggregation state, combination state and mixed color matching. Therefore, the rational selection of dyes is particularly important.
3. Choose dyes according to fiber properties and fabric usage
For cellulose fiber fabrics, dyes with good oxidation resistance should be used; for protein fibers, dyes with good reduction resistance or containing weak oxidizing additives should be used; for other fibers, dyes should be selected according to the effect on fading.
4. Dyes should be selected according to the color depth
A large number of tests have proved that the fastness to finish dyeing of reactive dyes on cellulose fibers is directly proportional to the depth of the color, that is, the darker the color, the better the fastness to finish dyeing. On the contrary, the lighter the color, the dye is mostly in a highly dispersed state on the fiber, and the probability of being exposed to the light is higher, and the final dyeing fastness will be significantly reduced. Therefore, for dyeing light-colored varieties, dyes with higher fastness should be used. In addition, many finishing agents such as softeners and anti-wrinkle finishing agents are added to the fabric, which will also reduce the product's fastness. Therefore, dyes that are not sensitive to these finishing agents should be selected.