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Bleaching plastic - peroxide concentration? 11 years 1 month ago #18810

HI!... Don't go any higher than the basic 3%. get a clear "GLASS" bowl and wrap it in aluminum foil. Shiny side towards the inside of the bowl. Make sure your white parts are very clean. Most parts will stay submerged but some u will need to hold them down with something. When the process starts you will notice a ton of air bubbles sticking to the parts. This will make them lighter and lift them to the surface. You will need to stir/flip parts occasionally and shake the bubbles off. To be honest, without the UV light the H/P doesn't do much. You have to use both together to get great results. I run a EXO-TERRA Repti Glo 10.0 UVB 26 Watt florescent light bulb installed in a small desk lamp. I hover the light inches from the H/P in the bowl. I then cover the top of the bowl and light with a cone made of aluminum foil. This concentrates all the UV light into the bowl. The heat from the light will slightly evaporate the H/P over time so you will need to top it up ever once and awhile. Depending on how bad the parts are you will unusually need to keep them under the light/H/P for at least 3-4 days. Some parts I have left up to 2 weeks. Most I leave for 5-7 days. 24 hours a day.

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Bleaching plastic - peroxide concentration? 11 years 1 month ago #18812

I'm gonna go in with a theory here - I'm gonna say the UV light is breaking down the unstable H/P molecules, so the stuff gives off oxygen bubbles, & it's the bubbling effect that's doing the cleaning, especially seeing as it takes so long.

Dunk the wheels in vinegar & throw some sodium bicarbonate in with them.... (Or coke with mentos, or similar).
There's a commercially available "bubbly cleaner" stuff, but I can't for the life of me remember what's it's called..... Vanish oxy-action? -try that

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Bleaching plastic - peroxide concentration? 11 years 1 month ago #18814

...

Spose the fundamental question is "What exactly is the "yellow" on old plastic, is it "on" or "in" the material, is it a physical or chemical change & is it reversible"


It's not that deep, it can be sanded off ... if it was pratical with that much fiddly detail :whistle:

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Bleaching plastic - peroxide concentration? 11 years 1 month ago #18815

...it's the bubbling effect that's doing the cleaning, especially seeing as it takes so long.
...


I don't think that can be the case, otherwise ultrasonic cleaning in plain water would take it off :(

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Bleaching plastic - peroxide concentration? 11 years 1 month ago #18819

Don't know then, just an idea, but then again, did you leave them in there for 2 days?
What else is in hydrogen peroxide that could be doing the cleaning?
I thought it was just stuff with loose oxygen that detaches itself & sticks itself to easily oxidised compounds (ie to form an oxide of that compound, as if you burned it).
The only other thing it does is fall to bits to give oxygen-gas & water (fairly quickly in an open container), particularly if you put energy into it, eg heat, high energy electromagnetic waves (UV light) etc to help break the weak H2O-O bonds

sorry, 1-2 weeks not days

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Last edit: by eddrick. Reason: misread post

Bleaching plastic - peroxide concentration? 11 years 1 month ago #18821

HI!... I believe the UV light is doing 80% of the whitening. I've tried it without the UV light and nothing much happens. Maybe 10% lighter. I've tried it with just the UV light and about the same 10%. It's weird how both components have to work together to get the end result.

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Bleaching plastic - peroxide concentration? 11 years 1 month ago #18823

Do an experiment using the same setup, but use heat rather than UV light (Also put it somewhere dark so sunlight doesn't affect the experiment) & let us know what happens.
Don't cover the bowl though, pure oxygen can be dangerous.

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Bleaching plastic - peroxide concentration? 11 years 1 month ago #18839

I think it is the UV light that does the job (probably in conjunction with a chemical process from the peroxide). The RC10 boys are very keen on this for whitening suspension parts. See here.
I've also heard that a UVB bulb (for a reptile terrarium) can be helpful.

Apparently peroxide works on ABS too.

Interesting reading here. suggests putting some "Oxy action" laundry power (e.g. Oxyclean) in with the peroxide. However, extreme caution should be taken when mixing chemicals (e.g. bleach can produce Chlorine gas = nasty).

The same site also suggests that stronger peroxide is NOT better.

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Last edit: by Martin Bell.

Bleaching plastic - peroxide concentration? 11 years 1 month ago #18854

Just a quote from this article :

The UV in the sun reacts with the Oxi and hydrogen peroxide, which liberate bromine atoms from the plastic. (the bromine is what makes the plastic yellow)


They added Oxi Action btw...

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Last edit: by Edou.

Bleaching plastic - peroxide concentration? 11 years 1 month ago #18889

Bromine? Nice, skin cancer all round then....

As for UV reacting with anything, what?! UV is an electromagnetic wave, it's not a chemical.... It's behaving like a low energy microwave on the process, introducing energy, exciting electrons etc

Another thought is that there could be some ion exchanging going on, not really sure as I thought Bromine formed -ve ions. Maybe the end result is H2Br + O2 gas or something.

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