Application of fabric color fastness test standard to printed fabrics

I. Introduction Color fastness to water is an important test item for textiles, and it is one of the assessment indicators stipulated in the mandatory national standard GB18401 'Basic Safety Technical Specifications for National Textile Products'. At present, the color fastness standard of textiles used in my country is GB/T57131997, and the color fastness test of this standard is equivalent to the international standard ISO105-E01:1994. The level of color fastness to water is directly related to the performance of textiles. However, there is a special situation in the actual test, that is, some printed fabrics will have obvious visible marks after being soaked and dried in water. The fastness was tested, but it was found that the fastness level of the test was very high, so there was a phenomenon that the test results could not reflect the actual performance. 2. Test principle The test principle of color fastness to water in the standard GB/T57131997 is to sew the textile and the lining fabric together, soak in the test water, squeeze out the water, and place it in a perspiration fastness tester for pressure treatment; Then put it in an oven at 37°C for 4 hours, take it out, and then hang it in the air at no more than 60°C to dry; after drying, use the discoloration and staining gray card to evaluate the discoloration of the fabric and the staining grade of the lining. 3. Problems in the application of standards 1. Standard test results The problem samples tested in this test are reactive dye printing fabrics, white and dark blue. Tested according to GB/T57131997, its discoloration level and staining level are both 4-5, which has reached the most stringent A-class 3-4 requirements of GB18401, and the detection level is very high. 2. Actual use situation According to the standard test results, a qualified report on water fastness can be issued, but the clothing made of this fabric has obvious problems in actual use, and prints appear after soaking and drying. As shown in Figure 1. 3. Analysis of standard problems 1. The production of imprints The printed fabrics may still have unfixed dyes or hydrolyzed dyes. Reactive dyes are water-based, and they will migrate with the movement of water during the drying process after washing. Dye deposits form on the surface, and imprints are formed where the dye accumulates. 2. Reasons for the appearance of imprints but the test is qualified 1) In the test of standard GB/T5713, it has been treated in an oven at 37 ℃ for 4 hours before drying, and there is very little water before drying; but in self-washing and drying, the With relatively more water, swimming is more likely to occur. 2) GB/T5713 stipulates that when the sample is dried in the air, once it is found that there is an air-dried sample, it must be discarded and redone. The reason for this requirement is that when the sample with air-drying phenomenon is dried, the water dispersion is too fast, and the dye on the above will be unevenly distributed due to migration, so that the final result cannot be accurately judged. When washing and drying by themselves, it does not avoid air-drying. 3) This sample appears imprinted after washing and drying. The main reason is that the printing is white, and a little stain is very obvious. However, no staining was found on the lining cotton in the test, because the standard GB/T5713 test fabric used was small, with a size of only 4cm10cm, and the concentration of dye accumulated by swimming was not enough to produce obvious imprints. In fact, it can be seen from Figure 1 that only one imprint can be found in a larger area. 4. Recommendations 1. In terms of standard, light-colored printed or white-ground printed fabrics, and even light-colored dyed fabrics may have similar confusions, that is, the color fastness to water is fully qualified after the standard test, but the samples may be larger Imprints will appear when immersed in water to dry due to the accumulation of dye migration. In addition to GB/T5713 and the equivalent ISO105-E01: 1994, the current textile color fastness standards include the American Association of Dyeing and Chemists Standard AATCC107 and the Japanese Industrial Standard JISL0846. There are certain differences in the selection of lining fabrics and oven temperature. Some researchers have compared a large number of samples and found that the test results of different water fastness standards for the same fabric have small differences in discoloration and large differences in staining [1], but These standard detection principles and procedures are basically the same, and none of them can reflect the actual performance in such special cases. This kind of situation is that the dark part of itself is contaminated with the light part, which can be self-contaminated, but its color fastness is not bad enough to contaminate the lining, so it is necessary to establish an independent testing method for this type of product. There are two aspects that need to be studied in the detection method. One is the selection of the size of the sample. Because of the effect of dye accumulation in this case, the sample needs a sufficient area to appear. The second is the establishment of the rating method, because the discoloration is not uniform. It is its characteristics and requires a larger area of ​​overall evaluation, which requires the development of corresponding sample cards or descriptive regulations. 2. In terms of production, obvious imprints are found after washing this sample, which is undoubtedly a problem with fastness, but it is qualified by the current standard. For this type of fabric, special attention should be paid to this possible phenomenon in clothing production.If you rely on a qualified test report to put into clothing production, and only after the finished product is found to have imprints after washing, it will cause irreparable huge losses. Because this fabric is printed on white ground, and the color is dark, the difference is obvious, which requires the treatment of its color fastness to be much stricter than ordinary printing. If the color of the printed fabric is similar to the color of the ground, using the same process, even if there is an imprint, it may not be seen due to the cover of the ground color. Therefore, in the printing and dyeing production, strict requirements are required for such samples in each process of printing, color fixing and washing, and the omission of any process may cause problems. In fact, the sample with the problem this time has no imprints after re-fixing, soaping and rinsing by the printing and dyeing company. Learn more about washing color fastness test: http://www.shuixsld.com
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