In an earlier issue of natific news, we promised we'd be back to share with you the seven most crucial areas for a dye house to be in control of their color development.

This is not only sent to dye houses and vendor but to you as a retailer/brand too because working close with your supply chain partners is essential if you want to get your colors right.

In this first of seven news articles, we will guide you to become a top performing dye house by giving you insights on how to control the most important pre-treatment for cellulosic fibres: the Hydrogen peroxide (H202) bleaching process.

Various reasons such as efficiency, cost savings, easy handling, and being environmentally friendly makes the advantages of the process obvious. Let’s have a closer look.

What is H202 bleaching?
Peroxide bleaching is a process that gives the fabric good hydrophilicity (i.e. having 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 and waxes, seed shell residues, lignin and fibre accompanying substances). In certain cases, depending on the origin of the cotton, there can be also disturbing heavy metals like iron that cause catalytic damage to the fabric.

When H202 bleaching needs to be controlled
If you don’t want your final result to be yellowish, it’s important to get the process right. 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.

Make sure this is limited in all circumstances
One has to know that such a peroxide bleach is quite a harsh process for cotton. The fabric gets damaged due to the release of free reactive oxygen radicals. The long chain molecules will be broken and the fragmentaries show less viscosity giving less tear strength values to the fabric.

This damage caused to the fabric has to be limited.

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

How to determine the 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 (< 1second). 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 natific@support.com.

The next area that we will help you address is R/C, you don’t want to miss that one!


Sincerely,

your natific team


Ps. If you missed the natific news where we listed all 7 areas that your dye house should be able to control, click here to read it.





 

 











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