In this natific newsletter, we will guide you through how to control the most important pre-treatment for cellulosic fibres: Hydrogen peroxide (H202) bleaching.
This is not only important for dye houses and vendor but for retailers and brands too, because working close with your partners is essential if you want to get your colors right.
Various reasons such as efficiency, cost savings, easy handling, and being environmentally friendly makes the advantages of the process obvious.
What is H202 bleaching?
Peroxide bleaching is a process that gives the fabric good hydrophilicity (i.e. an affinity for water, readily absorbing or dissolving in water) and a constant degree of whiteness.
This is a pre-requisite when dyeing the desired shade in the most convenient way without facing too many problems.
The bleaching process is intended to remove any disturbing substances from the cellulosic fibre that may cause problems during dyeing (like fats, waxes, seed shell residues, lignin and fibre accompanying substances). In certain cases, depending on the origin of the cotton, there can be disturbing heavy metals like iron that cause damage to the fabric.
When do you need to control H202 bleaching?
H202 bleaching needs to be carried out mainly for pale and brilliant colors, where yellowish color of the cellulosic fibre would have negative impact on shade.
If you don’t want your final result to be yellowish, it’s important to get the process right.
Make sure this is limited in all circumstances!
Peroxide bleaching is a harsh process. The fabric gets damaged due to the release of free reactive oxygen radicals, giving less tear strength values to the fabric.
How to get your H202 bleaching right
The most common auxiliary to prevent too strong degradation of cotton is a peroxide stabilizer. This will help to get a safe and reliable bleaching process. As peroxide is not stable in alkaline conditions and will degrade over time, it needs to be stabilized over the whole bleaching cycle.
If the peroxide bleaching process isn’t stabilized, the cotton fabric will result in deviating degrees of whiteness within the lot and the tear strength values of fabric will be poor.
A well-balanced bleaching recipe must include auxiliaries as follows:
- Wetting agent with good washing and dispersing effect
- Peroxide stabilizer
- Sequestering agent
- Detergent with good emulsifying and soil suspending properties
Check your bleaching effect
The degree of polymerization (DP) has become industry standard to evaluate the bleaching process efficiency. The DP is between 2 500 – 3 000 before the bleaching process and should not fall below 1 800 after the bleaching.
Other quick test methods to check peroxide-bleaching efficiency:
- TEGEWA drop test for absorbency of fabric (< 1 sec). The drop should have circular expansion, not oval.
- Test of residual peroxide. After the bleaching process, 10-20% of actual peroxide amount should still be on the fabric.
We are happy to help you with your H202 bleaching process! Don’t hesitate to contact our support team at firstname.lastname@example.org.
your natific team