The yellowing of the surface of a white or light-colored substance in response to external conditions, such as light or chemicals. This phenomenon is called yellowing.

The yellowing of white and dyed textiles will not only damage their appearance, but also reduce their service life. Therefore, the research of textile yellowing causes and anti-yellowing measures has been one of the hot topics at home and abroad.

What are the causes of textile yellowing?

photoyellowing

Photoyellowing refers to the yellow surface of textile clothing caused by molecular oxidative cracking reaction caused by sunlight or ultraviolet light. Light yellowing is most common in light colored clothing, bleached and brightened fabrics. When the fabric is illuminated, the light energy is transferred to the fabric dye, which causes the dye conjugate to crack, resulting in the fading of the light, and the surface of the fabric appears yellow. Visible light and ultraviolet light are the main factors causing fading of azo dyes and phthalocyanine dyes, respectively.

Phenol yellowing

Phenolic yellowing is generally caused by the contact transfer of NOX and phenolic compounds on the fabric surface. The main reactive substance is usually the antioxidants contained in packaging materials, such as butylphenol (BHT). After a long time of packaging and transportation, the BHT in the packaging materials will react with NOX in the air, resulting in yellowing of the clothing.

Oxidative yellowing

Oxidative yellowing refers to the yellowing of fabric after oxidation by air or other substances. When dyeing and finishing textile clothing, reducing dyes or auxiliaries are usually used. After contact with oxidizing gas, REDOX action occurs and yellowing occurs.

Brightening agent yellow

Brightening agent yellowing mainly occurs on light-colored fabrics. When the remaining brightening agent on clothing surface migrates due to long-term storage, it leads to excessive local brightening agent and yellowing of clothing.

The softener turns yellow

The cations in the soft additives used in the post-finishing process will oxidize when subjected to heat, light and other conditions, resulting in yellowing of the soft processing parts of the fabric.

What are the testing standards for yellowing resistance of textiles?

Test method for yellowness caused by natural light exposure :GB/T 8427-2008 "Textile Color Fastness test to artificial light Color fastness: Xenon arc" The test principle is to put the sample together with a group of blue wool standard samples in the box, under the artificial light source in accordance with the specified conditions, and finally the sample and blue wool standard samples for color color rating, evaluation of color fastness.

Test method of yellowing caused by ultraviolet light exposure: GB/T 30669-2014 "Textile color fastness test to light yellow color fastness" The test principle is that the sample is irradiated under ultraviolet light for a certain time, compared with the unirradiated sample, with the evaluation of discoloration with gray sample card grade.

Test method for yellowing caused by phenolic substances: GB/T 29778-2013 "Evaluation of Potential Phenol Yellowing for Color Fastness tests of Textiles", SN/ T2468-2010 "Test Method for Phenol yellowing of Import and Export Textiles", the test principle is to put each sample and control fabric in a test paper containing 2,6 ditert-butyl4-nitrophenol (BHT). It is placed between glass plates and superimposed on top of each other. A test pack is formed by wrapping it tightly with BH free polyethylene film and placed in an incubator or oven at the specified pressure for a certain period of time. The possibility of phenol yellowing in the sample was evaluated by evaluating the degree of yellowing of the sample with the gray sample card.

Test method of fabric yellowing caused by chlorine bleaching: FZ/T 01078 -- 2009 "Test method of Fabric chlorine yellowing" The test principle is to compare the sample with the original sample after chlorine bleaching, cleaning and drying in the washing machine, so as to evaluate the yellowing grade of the sample.

How to prevent the yellow of textile fabric?

(1) In the production and processing process, the enterprise should try to reduce the use of brightening agent, shall not exceed the yellowing point of brightening agent.

(2) When finishing and shaping the fabric, the temperature should not be too high. High temperature will make the dye or auxiliary agent on the fabric surface oxidize and crack, and then cause the fabric yellowing.

(3) In the process of packaging, storage and transportation, use packaging materials with low BHT content, and try to keep the storage and transportation environment ventilated at room temperature to avoid phenol yellowing.

(4) In the case of phenolic yellowed due to packaging of textile and clothing, in order to reduce losses, a certain amount of reducing powder can be scattered on the bottom of the package, the carton can be sealed for 1 to 2 days, and the carton can be opened and placed for 6h. After the odor has dissipated, the yellowed can be repaired to the maximum extent.

(5) In daily wear, should pay attention to maintenance, wash frequently and wash lightly, should not be exposed to the sun for a long time.