The surface of white or light-colored substances turns yellow under the influence of external conditions such as light, chemicals, etc. This phenomenon is called “yellowing”.
When white textiles and dyed textiles turn yellow, not only their appearance will be damaged, but their service life will also be reduced. Big discount. Therefore, the study of the causes of textile yellowing and anti-yellowing measures has always been one of the hot topics at home and abroad.
What are the causes of yellowing of textiles?
Light yellowing
Photoyellowing refers to the discoloration of textile clothing due to exposure to sunlight or ultraviolet light.
Causes oxidative cleavage reaction of molecules, causing the surface of clothing to turn yellow. Photoyellowing is most common in light-colored clothing, bleached fabrics, and whitening treated fabrics. After the fabric is illuminated, the light energy is transferred to the fabric dye, causing the dye conjugate to cleave, causing light fading and the surface of the fabric to appear yellow. Among them, visible light and ultraviolet light are the main factors causing fading of fabrics dyed with azo dyes and phthalocyanine dyes respectively.
Phenol yellowing
Phenol yellowing is generally caused by the contact transfer of NOX and phenolic compounds on the surface of fabrics. The main reaction substance is usually antioxidants contained in packaging materials, such as butylphenol ( BHT). After clothing and footwear are packaged and transported for a long time after leaving the factory, the BHT in the packaging materials will react with NOX in the air, causing the clothing to turn yellow.
Oxidative yellowing
Oxidative yellowing refers to the yellowing of fabrics caused by oxidation by the atmosphere or other substances. Textile garments usually use reducing dyes or auxiliaries during dyeing and finishing. After contact with oxidizing gases, oxidation-reduction occurs and yellowing occurs.
Whitening agent turns yellow
Whitening agent yellowing mainly occurs on light-colored fabrics. When the residual whitening agent on the surface of the clothing migrates due to long-term storage, resulting in local excessive whitening agent, And produce clothing yellowing.
Softener yellowing
When the softening additives used in the finishing process of clothing are exposed to conditions such as heat and light, the cations in them will oxidize, causing the softened parts of the fabric to turn yellow.
What are the testing standards for textile yellowing resistance?
Test method for yellowing caused by natural light exposure: GB/T 8427-2008 “Textiles Color fastness test: Color fastness to artificial light: Colored wool standard samples were used to grade discoloration and evaluate color fastness.
Test method for yellowing caused by ultraviolet light irradiation: GB/T 30669— 2014《 Textile color fastness test “Color fastness to light yellowing” The test principle is that after the sample is irradiated under ultraviolet light for a certain period of time, it is compared with the sample that has not been irradiated, and the gray sample card for assessing discoloration is used to evaluate the discoloration grade.
Test method for yellowing caused by phenolic substances: GB/T
29778-2013 “Textiles Color Fastness Test
Evaluation of Potential Phenol Yellowing”, SN/T2468-2010 “Test Method for Phenol Yellowing of Imported and Exported Textiles”, the test principle is to sandwich each sample and control fabric in a container containing 2,6 di-tert-butyl 4-nitrophenol ( BHT) test paper, place it between glass plates and stack them together, wrap them tightly with BH-free polyethylene film to form a test package, put it in a constant temperature oven or oven for a certain period of time under the specified pressure. Use the gray sample card for stain assessment to evaluate the yellowing grade of the sample to evaluate the possibility of the sample producing phenol yellowing.
Test method for fabric yellowing caused by chlorine bleaching: FZ/T 01078—2009《 Test Method for Chlorine Absorption and Yellowing of Fabrics” The test principle is to evaluate the yellowing level of the sample by comparing it with the original sample after bleaching, cleaning and drying with chlorine in a washing machine.
How to prevent textile fabrics from yellowing?
(1) Enterprises should minimize the use of whitening agents in the production and processing process , shall not exceed the increaseThe yellowing spots of the agent.
(2) When finishing and shaping the fabric, the temperature should not be too high. High temperature will cause oxidative cracking of dyes or additives on the surface of the fabric, which will cause the fabric to turn yellow.
(3) During the packaging, storage and transportation processes, use packaging materials with lower BHT content, and try to keep the storage and transportation environment at room temperature and ventilated to avoid phenol yellowing. .
(4) When textiles and clothing produce phenol yellowing due to packaging, in order to reduce losses, a certain amount of reducing powder can be sprinkled on the bottom of the packaging and the carton sealed. Pack for 1 to 2 days, then unpack and leave for 6 hours. After the smell has dissipated, you can repackage, so that the yellowing can be repaired to the greatest extent.
(5) When wearing it daily, you should pay attention to maintenance, wash it frequently and lightly, and avoid long-term exposure to the sun.
