The color fastness of textiles usually includes resistance to soaping, rubbing, light, bleaching or oxidizing agents (reducing agents), ironing resistance, perspiration resistance and perspiration light color fastness, etc. Among them, soaping resistance, friction resistance, light resistance, water resistance and perspiration resistance are several color fastness indicators that most buyers pay high attention to in actual production and trade.
Color fastness ratings are: Level 1, Level 1-2, Level 2, 2-3 Level, level 3, level 3-4, level 4, level 4-5, level 5. Level 5 and level 9. Level 1 is the worst, level 3 is basic, and level 5 is the highest, but it’s almost impossible. Level 3 can only be a basic level, an intermediate level.
Color fastness to soaping
1. Resistance to soaping Color fastness test method
Color fastness to soaping is one of the most 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 on a standard gray card. The results are divided into 5 levels, with level 5 being the best and level 1 being the worst.
2. 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 at level 3 or above. Level 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 on the cloth surface and the transfer of some colored fiber particles, and is therefore related to the type of dye used, the dyeing process and the post-processing process.
3. The color fastness of reactive dye dyeing products to soaping depends on the unfixed Dyes
Take reactive dyes as an example. Theoretically, since dyes form covalent bonds with fibers, washing with water cannot easily cause dye desorption, fading and bleeding. Therefore, The soaping color fastness of reactive dye dyed products depends on the amount of unfixed dyes (hydrolyzed dyes and a small amount of unreacted dyes). 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 that affect the color fastness to soaping are the dye structure and properties, followed by dyeing and post-dyeing treatments. 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.
4. 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 color 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-processing, and the color fastness to soaping is good.
Color fastness to rubbing
1. Comparison of testing methods for color fastness to rubbing
The color fastness to rubbing test is Refers to the test in which the colored sample is rubbed with dry rubbing cloth and wet rubbing cloth respectively, and then the degree of staining of the rubbing cloth is evaluated. The test results are divided into 5 levels, with level 5 being the best and level 1 being the worst. Although the testing process is simple, it is the most basic color fastness assessment indicator for textile products. It is almost one of the items that buyers from all over the world must assess when placing orders. The technical conditions of rubbing fastness testing standards in various countries are very similar, but there are also some differences.
2. Main factors affecting color fastness to rubbing and their control measures
During the process of friction between textiles and other objects, the color shedding or staining of the rubbed objects is affected by many factors. There are two ways of color shedding and staining: one is that the dye on the textile falls off or fades and is stained on the surface of the friction object; the other is that the dyed fibers fall off and adhere to the surface of the friction object.
3. The main reason for staining
Although they have different chemical structures There are certain differences in the covalent bond strength and adhesion between reactive dyes and cellulose fibers, but their effects on the wet rubbing fastness of dyed fabrics are basically the same. When dyed fabrics are wet rubbed, the covalent bonds formed between the dye and the fiber will not break and cause floating color. The transferred dye usually does not form a covalent bond with the fiber, but only relies on van der Waals forces to produce adsorption, that is, floating color.
Light fastness
1. Lightfast colorwash.
3. Color fastness to rubbing:
Place the sample on the rubbing fastness meter , rub it with a standard rubbing white cloth for a certain number of times under a certain pressure. Each group of samples needs to be tested for dry rubbing color fastness and wet rubbing color fastness. Use a gray card to rate the color stained on a standard rubbing white cloth, and the resulting grade is the measured color fastness to rubbing. Rubbing color fastness requires two tests, dry rubbing and wet rubbing, and all colors on the sample must be rubbed.
4. Sunlight color fastness:
Textiles are usually exposed to light when used, and light energy can destroy dyes and cause the well-known The “fading” of colored textiles causes the color of colored textiles to change, generally becoming lighter or darker, and some will also change the color light. Therefore, it is necessary to test the color fastness. The color fastness test is to test the sample with different fastnesses. The graded blue wool standard cloth is placed together under specified conditions for sunlight exposure. The sample is compared with the blue wool cloth to evaluate the light fastness. The higher the grade of the blue wool standard fabric, the more lightfast it is.
5. Color fastness to perspiration:
Sew the sample and the standard lining fabric together, put it in the perspiration solution, and then clamp it on the perspiration color fastness meter, put it in the oven at constant temperature, and then dry it, and use a gray card to grade it and get the test results. . Different testing methods have different sweat liquid ratios, different sample sizes, and different testing temperatures and times.
6. Water stain color fastness:
Test the sample treated with water as above.
7. Chlorine bleaching color fastness: After washing the fabric in chlorine bleach under certain conditions, evaluate the degree of color change. This is Color fastness to chlorine bleaching.
8. Non-chlorine bleaching color fastness: After washing the fabric under washing conditions with non-chlorine bleaching, Evaluate the degree of color change, which is the non-chlorine bleaching fastness.
9. Pressing color fastness:
Dry test After the sample is covered with cotton lining fabric, it is pressed for a certain period of time in a heating device with specified temperature and pressure, and then the gray sample card is used to evaluate the discoloration of the sample and the staining of the lining fabric. The color fastness of hot pressing includes dry pressing, tidal pressing and wet pressing. The specific test method should be selected according to different customer requirements and testing standards. </p
