Problems in the application of textile color fastness standards
1. Introduction
Water-resistant dyeing fastness is an important test item for fabric products and is one of the assessment indicators stipulated in the mandatory national standard GB18401 “National Basic Safety Technical Specifications for Fabric Products”. Currently, the water-resistant dye fastness standard of fabrics used in my country is GB/T5713-1997. The dye fastness test of this standard is equivalent to the international standard ISO105-E01:1994. The level of water-resistant dyeing fastness is directly related to the performance of fabric products. However, there is an unusual situation in actual testing, that is, some printed fabrics will produce obvious visible marks after being soaked in water and dried. However, according to current standards The water fastness was tested, but it was found that the tested fastness level was particularly high, so the test results did not reflect the actual performance.
2. Testing principle
The testing principle of water-resistant dyeing fastness in standard GB/T5713-1997 is to sew the fabric and the backing fabric together, soak them in test water, squeeze out the water, and place them in a perspiration fastness tester. Pressure treatment; then put it into an oven at 37°C for 4 hours, take it out, and then hang it in the air not exceeding 60°C to dry; after drying, use the discoloration and staining gray card to evaluate the discoloration of the fabric and the staining level of the lining.
3. Problems in the application of standards
3.1 Standard test results
The problem sample tested in this experiment is a reactive dye printed fabric, with a white background and dark blue color. Tested according to GB/T5713-1997, its discoloration level and staining level are both 4 to 5 levels, which has reached the strict Class A “≥ 3 to 4 level” requirements of GB18401, and the detection level is particularly high.
3.2 Actual usage
According to the standard test results, a qualified report on water-resistant dyeing fastness can be issued. However, the work clothes made of this fabric have obvious problems in actual use, and marks appear after soaking and drying. As shown in Figure 1.
3.3 Analysis of standard issues
3.3.1 The production of imprints
The printed fabric may still have unfixed dyes or hydrolyzed dyes remaining. Reactive dyes are water-based and will migrate with the rest of the water during drying after washing, forming dye accumulation on the surface of the fabric. Imprints will be produced.
3.3.2 Reasons why marks appear but pass the test
1) In the test of standard GB/T5713, it has been processed in an oven at 37°C for 4 hours before drying. There is very little moisture before drying; however, during self-cleaning and drying, there is relatively more moisture in it. Migration occurs more easily.
2) GB/T5713 stipulates that when the sample is dried in the air, once an air-dried sample is found, it must be discarded and redone. This requirement is due to the fact that when the air-dried sample is drying, the water is dispersed too quickly, and the dye on it will be unevenly distributed due to migration, making the final result unable to be accurately judged. And when cleaning and drying by yourself, you don’t avoid air drying.
3) This sample has marks after being dried after washing. The main reason is that the print is printed on a white ground, and a little stain will be very obvious. However, no staining of the lining cotton was found during the test. This is because the standard GB/T5713 test fabric adopted is small, with a size of only 4cm × 10cm, and the concentration of migrating and accumulated dye is not enough to produce obvious marks. In fact, as can be seen from Figure 1, only one mark can be found on a larger area.
4. Suggestions
4.1 Standard aspects
Similar confusion may occur with light-colored printed or white printed fabrics, or even light-colored dyed fabrics. That is, the water-resistant dyeing fastness is fully qualified after standard testing, but larger samples may be soaked in water to dry. When dry, marks will appear due to dye migration and accumulation. In addition to GB/T5713 and the equivalent ISO105-E01:1994, the current water fastness standards for fabrics include the American Association of Colorists and Chemists standard AATCC107 and the Japanese Industrial Standard JISL0846. These standards have certain differences in terms of constant temperature time, selection of lining fabrics, and oven temperature. Through a large number of sample tests, some researchers found that different water-resistant dyeing fastness standards have little difference in the color change of the same fabric in the test results. The stain color varies greatly [1], but these standard detection principles and processes are basically the same, and they cannot reflect the actual performance of such extraordinary situations.
This kind of situation occurs when the dark part of itself contaminates the light part. It can be “self-stained”, but its dyeing fastness is not so bad that it contaminates the lining. Therefore, it is necessary to detect this type of product. method. There are two aspects that need to be studied in the detection method. One is the selection of sample size, because the effect of dye accumulation in this situation requires a sufficient area for the sample to appear; the other is the accuracy of the rating method, because the discoloration is uneven. It is its characteristic that it requires an overall evaluation of a larger area, which requires the development of corresponding sample cards or descriptive regulations.
4.2 Production
After washing this sample, obvious marks were found, which undoubtedly indicates a problem with the fastness. However, it passed the test according to current standards. For this type of fabric, we need to pay great attention to this possible phenomenon in the production of work clothes. If we go into the production of work clothes based on a qualified test report, only to find out after the finished product that there are marks after washing will cause huge irreparable losses.
Because this fabric is printed on a white ground, and the color is dark, the difference is obvious, which requires its dyeing fastness to be treated better than ordinary printing.Much more expensive. If the pattern and color of the printed fabric are similar to the ground color, even if “imprints” appear using the same process, they may not be visible due to the cover up of the ground color. Therefore, in printing and dyeing production, strict requirements are required for such samples in the printing, color fixing and cleaning processes. Omissions in any process may cause problems. In fact, the sample with the problem this time was later re-fixed, soaped and rinsed by the printing and dyeing company, and no traces appeared again.
AAASDGGERY6UFGH
Extendedreading:https://www.alltextile.cn/product/product-27-319.html
