Phenolic Yellowing Test Method in Textile Industry

Last Updated on 16/01/2021

Phenolic Yellowing in Textile

Md. Shafiqul ISLAM (Newton)
Manager –Softlines lab, Epyllion Testing Lab Ltd,
Gazipur, Dhaka, Bangladesh


It is the discoloration of textiles caused by the action of oxides of nitrogens on yellowable phenols. For phenolic yellowing to take place three components are required; yellowable phenols (OH), oxides of nitrogen (NOx) and certain pH conditions.

phenolic yellowing of white fabric
Fig: Phenolic yellowing of white fabric

During the production process, when storing and when using the goods. It can also have different cause. Often, yellowing concerns a reaction with phenols. This we call phenolic yellowing or gas fading by NO2.

phenolic yellowing or gas fading by NO2

Apart from the frequent attack on white or pastel shades, dark shades are also affected, which becomes duller in appearance. It can occurs by fiber degradation, by color break down by chemical destruction.

The test papers are impregnated with a methanol solution containing the phenolic compound and oxides of nitrogen. The pH conditions are provided by the material under test. The yellowing comes from the phenols. Chemically, the yellow substances form through nitration and/or oxidation of specific phenolic substances often found to be present in antioxidants and preservatives. The control fabric goes yellow (dark lemon), during the test, ensuring that correct test conditions have been used. BHT-free film is utilized during the test to ensure that the yellowing that has occurred is not due to products within the film.

What is the Test Method Used for?
The phenolic yellowing test method is a simple predictive test, typically used to assess the potential of white or pastel-coloured textiles to transit or storage yellowing. It is specifically for phenolic yellowing i.e. the discoloration of textiles caused by the action of oxides of nitrogens on yellowable phenols. The test is not intended to deal with many other causes of discoloration, i.e. migration or fading of optical brightening agents, gas fume fading, the oxidation of fabric lubricants and so on.

Outline of Test
The risk of yellowing is evaluated by a contact test. Each test specimen is folded between a phenol-impregnated test paper. The test package consists of 5 test specimens and one standard control fabric wrapped and sealed in BHT-free polythene film. A Perspirometer maintains constant pressure on the package, and an incubator provides the specified environmental conditions. On removal from the incubator the specimens are compared with their original and the intensity of yellowing assessed using the standard Grey Scale for Assessing Staining.

Phenolic yellowing testing
Fig: Phenolic yellowing testing

Which color affected most:
Basically in all textile all colors affected by this. Specially it is very visible on light color and white. When it is dark color we found shade little bit duller.

Out of the box it can be happened:
If fabric long term exposure to heat or light or some time even by blending certain fabric. Visible when we use softeners, lubricants, OBA or salts. Some time by ozone [denim] or other elements in the air. Some times by using perfumes, lotions, medicines, detergents, washing softeners, starch etc.

What can we do to avoid it:
However quality is a cloudy topics. But if your product make into yellow that is not comfortable for you.

So, we should avoid it by:

  • Using BHT free polythine.
  • Maintaining PH 6 or below 6.
  • Make free your production area from oxides of nitrogen.
  • Using finishing chemical free from phenolic compound
  • Using non ionic or anti-ozone softener.

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