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Description of test requirements for yellowing fastness of textiles
The common yellowing in textiles mainly includes optical yellowing and phenolic yellowing. The former refers to the yellowing of the textile surface caused by sunlight or ultraviolet light; the latter refers to the yellowing of the textile surface caused by nitrogen oxides or phenolic compounds. Compared with conventional color fastness tests such as water resistance and perspiration resistance, the standard and test of textile yellowing fastness started relatively late.
Two test methods for yellowing of textiles:
1. Light yellowing test This unit has carried out certain research on the light yellowing test of textiles. The method used is basically similar to the test method for light fastness of textiles, only the light source used is different. The basic test principle is to cover the head and tail parts of a rectangular textile with a shading sheet, and then place it in a special test box. The change of the color of the light part of the sample, according to the GB250 gray sample card to evaluate the degree of discoloration of the sample, so as to determine the ability of the textile to resist light yellowing. The schematic diagram of the test is shown in Figure 1. Figure 1 Schematic diagram of textile light yellowing test 
2. Phenolic yellowing test According to Caurtauldsmethod and ISO105-X18:2007, the test device for phenolic yellowing test is basically the same as the commonly used test instrument for color fastness to perspiration. The sample to be tested and a piece of fabric for time control were wrapped with test paper containing phenol and then sandwiched between glass plates to form a combined sample. After applying a certain pressure, wrap it with polyethylene film and place it in an oven at a specified temperature. , remove it after a period of time, disassemble the polyethylene film after cooling, take out the control fabric and the sample and immediately use the GB251 gray sample card to evaluate the staining grade of the sample. If the staining of the control fabric reaches a predetermined value, the staining level of the sample is the test value, otherwise, the test is repeated. Assessmentofthepotentialtophenolicyellowingofmaterials.
Description, analysis and discussion of the test requirements for textiles' yellowing fastness.
From the above description, we can see that the light-yellow colorfastness of textiles mainly refers to the discoloration of textiles under a certain relative humidity and temperature environment after being irradiated by ultraviolet light or ultraviolet/visible light. Phenomenon, in general, it will be equivalent to the light fastness of textiles, but in fact the two concepts are essentially different: the light fastness test is mainly about the fading degree of dyes on textiles after exposure to light; and the evaluation of light yellowing It is the light yellowing of textiles caused by the addition of chemicals such as bleaching agents during processing. At present, the standard HG/T3689-2001 'Test method for resistance to yellowing of footwear', which is used for testing textile light yellowing, is mainly applied to the evaluation of light yellowing of white or light-colored shoe materials. limitations. The phenomenon of phenolic yellowing of textiles is mainly due to the reaction of phenolic antioxidants (BHF) contained in packaging materials with nitrogen oxides (NOX) in the air during packaging, transportation or storage of textiles, resulting in yellowing or discoloration of textiles. Change. The test methods of Caurtauldsmethod and ISO105-X18:2007 both simulate the environment of phenolic substances that textiles may come into contact with during packaging, storage and transportation, and have good guiding significance for the evaluation of phenolic yellowing of textiles. my country should formulate relevant standards as soon as possible.
Conclusion In view of the above analysis, this paper summarizes the following suggestions:
Compared with the test of phenolic yellowing, the test of light yellowing of textiles is still in its infancy. In the future standard formulation and method research, more attention should be paid to the testing standards of textiles on the basis of the currently used test standards for shoe materials. The characteristics of the test, such as temperature and humidity, light time, etc., are carefully analyzed and studied to more truly reflect the light yellowing performance of textiles. The yellowing fastness test of textiles requires that in white or light-colored products such as wool, silk, man-made fibers, and leather, bleached textiles all have yellowing phenomena to varying degrees, some occur during processing, and some occur in In the process of use, no matter which one has a serious impact on the appearance quality of the product. But so far, such tests and assessments in China are mainly limited to export products. Due to the lack of standards and methods, most domestic enterprises have not yet had relevant assessments.
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