There a quite a few ways to whiten a fabric, and I would like to discuss a couple of them; specifically chlorine bleach and hydrogen peroxide. They are the most common methods and often how they are made and how their usage works is unknown to many.
Bleach, otherwise known as Sodium Hypochlorite, is made by combining sodium hydroxide (lye) with gaseous or liquid chlorine and then diluting this solution with water.
It whitens through the chlorine, which breaks down the natural color or pigmentation of the fabric (this also breaks down stains and such). Chlorine, which can be quite dangerous on its own and needs the lye to hold onto to keep it stable, hence the purpose of the lye and not just straight chlorine. This method of whitening, will produce the whitest white one can get for a fabric and is much cheaper for whitening than other methods. This method is also more abrasive and can affect the life of the fabric.
Bleach sound pretty simple, right? Well, Hydrogen Peroxide… not so much. This helps to get an idea of probably why the Bleach method is cheaper and more commercially available for whitening of fabrics.
Hydrogen Peroxide is basically commercially made by first using palladium to cause 2-alkyl anthraquinone and two hydrogen molecules to react and combine creating 2-alkyl anthrahydroquinone (the palladium is just used to cause the reaction and is not in the 2-alkyl anthrahydroquinone). Two oxygen molecules are then added to the 2-alkyl anthrahydroquinone. Now you basically have 2-alkyl anthraquinone and hydrogen peroxide combined into one compound because the added hydrogen and oxygen create hydrogen peroxide. The hydrogen peroxide is extracted from the compound using distillation, which separates the 2-alkyl anthraquinone from the hydrogen peroxide. The 2-alkyl anthraquinone is only used to get the hydrogen peroxide to combine and form properly and is not in the end product of hydrogen peroxide, it is necessary because attempting to combine the two hydrogen atoms and oxygen atoms directly can often times result in the wrong compound being formed.
Hydrogen Peroxide whitens through oxygenation from the oxygen atoms in the hydrogen peroxide that easily separate from it and bonds onto the pigment, removing it from the material. Fabrics colored using this method produce a less strong white, though this whitening method is less abrasive on the fabric itself.
Overall, I hope this has explained some of the basics with common fabric whiteners! Let me know if you want to know anything further or additional about them! Lastly, don’t forget to post in the comments your ideas for the next blog post!
Sources for information provided:
http://chlorine.americanchemistry.com/FAQs/Chlorine-Bleach http://alpha.chem.umb.edu/chemistry/ch471/documents/Hydrogenperoxide.pdf http://nzic.org.nz/ChemProcesses/production/1E.pdf