Online there are multiple how-too's for whitening yellow plastic. The process even got a name "retrobrite" because many dorks like us use these methods to restore old game console and computer cases.What i am trying to determine in this question is the underlying chemical process that all these methods contribute to.
The methods used are:
1. Hydrogen peroxide + UV light
2. Hydrogen peroxide + elevated temperature
3. Ozone from ozone generator + UV
4. Ozone from ozone generator + elevated temperature.
Elevated temperature (above 60*C) induced bleaching effect of peroxide, is a well known phenomenon. So it makes sense that peroxide+heat works better than just peroxide.
So my first thought would be bleaching effect of peroxide, but then the need for UV light is irrelevant. https://en.wikipedia.org/wiki/Peroxide-based_bleach
well not completely irrelevant, but somewhat. O=O or O-H bond is 5.15eV (https://en.wikipedia.org/wiki/Bond-dissociation_energy
) which is equivalent to UV at 238nm.
Ozone has dissociation energy of 3.76eV per bond, so that is 329nm.
My point being that the basic UV lamps that most people buy are 390 or 365 nm wavelength... sooo only a small fraction of accidental high energy UV rays from those lamps actually does any work?
Or is there more to the chemistry of brightening the plastics than just formation of reactive oxygen?
The elevated temperature with peroxide definitely works, but all i can see from elevated temperature is increase of reaction rate, i can't see any mechanism, such as UV that would form reactive oxygen...
What am I missing?
Is there something else going on?