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Removing yellowing from plastics - Part 2

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Yes Lorne, the mixture was sticky enough to tack onto verticals. It's a bit thixotropic so brushing it on thins it down slightly, however, enough of it sticks to ensure that it works.

I also had to re-apply it as I stopped at two hour intervals to take the photos. A bit of a pain but worth it for the information it gave us.

The gel is stable until you add the 'Oxy', so you could make a batch of gel and store it until you need it.
 
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@ Merlin:
BTW, that case wasn't yellow, it was brown !

When I first tried the XG, I had to apply some additional mix too - the stuff is so thick and sticky, it's tough to apply it onto all portions of the part in the same thickness. I'm wondering if something like a putty knife would be better than a brush for application. The mixture seems to want to stick to the brush as well as the parts.

I've got a batch going at the moment. 1 pint of H202, 1 tsp of xanthan gum & 1 tsp of isopropyl alchol (I like fast), and 1/2 tsp of Oxy.

I tried mixing the XG and alcohol first and they mixed nicely. I added a little H202 and it lumped up like crazy, so I added the rest of the H202 and put the whole thing into my kitchen Osterizer blender. That mixed it up real good, with no lumps anywhere. It gets a bit foamy beause of all the air getting mixed in - makes it sticky though, which is good. Then I added the Oxy.

After this batch, I think I'm going to be able to decide whether I prefer the XG or the powdered bleach better. I know the PB is faster, and the parts do smell real nice afterward (really - I checked), but I'll see how they compare with the actual de-yellowing performed.
 
Merlin said:
OK,

I have a test in progress involving a 1985 'breadbox' Commodore 64 that is browner than George Hamilton / Dale Winton / David Dickenson / insert overtanned celebrity here.

My mixture is:-

1 pint 35% H2O2
1 teaspoonful xanthan gum (Kelzan D to be precise)
1/2 teaspoonful 'Vanish Oxy Action Plus'
I teaspoonful glycerine

I dispersed the gum in the water, glycerine and peroxide using a food mixer.
Click to expand...

"dispersed the gum in the water"

What water?
There's no water in your list of ingredients.

C'mon Merlin, you're not writing an MSDS - what else are you putting in there that you're not telling us about? Quit holding back on us.
 
@ Lorne

Sorry, I meant the H2O2, my mistake.....

I used a Braun stick hand blender. I added the xanthan gum and H2O2 together along with the teaspoonful of glycerine then gave it about 30 seconds of blending in short bursts. This made a smooth mix with no lumps. I then added the Oxy, gave it another 10 seconds then applied it to the case.

I have to admit I am chuffed with the results, that's about the most severe test we have ever given it and it has worked. It also seems pretty goof-proof as long as you watch the temperature and don't over do the Oxy.
 
OK, I've got to give the thumbs up to the hairdreser's powdered beach & H2O2 mixture. I tried the xantham gum mixture, checked it after four hours and it hadn't done the job. In addition, it was spotty in its coverage. I washed off the pieces and coated them with the H2O2 and powdered bleach mixture and in two hours they were fine. The PB mixture sticks to the verticals better than the XG as well. You just can't use the PB mixture when there's painted parts involved.

Merlin:
You've got to gve this PB mixture a try. It doesn't bubble like the other mixtures though. That makes me think that there isn't enough TAED in the PB mixture. Do you see any danger in adding the Oxy to the PB mix? I'm thinking that could improve the process.

RE: a previous reply of yours regarding garden chairs; I was sitting on the deck after coating the computer casing parts, and was looking at my deck chairs. In Phoenix, AZ we get over 300 days of sunshine per year, so everything weathers badly (incl garden hoses, deck chairs & people). I had chairs that used to be a green color, but after two years in the sunshine, are now brown. I tried a pressure washer on them, and that didn't get them any lighter. I had a little H2O2 solution left over, so I thought what the hell, the chairs are toast, why not try a little of the solution on them?

(The back, far right chair is the one I treated).

Here's what they looked like before:
Lawn chairs 002.jpg
And here's what they looked like after (top and bottom right side are the sections I treated)
Lawn chairs 004.jpg
It was just a couple of test patches, but the rest of the chairs will now get the treatment.
 
Well done mate, that's not a bad call, using it on garden chairs. I bet you are walking aound the house now, looking for things to clean up; careful, it could become an obsession.....:mrgreen:
 
Very good so far on these tests. Yes, the PB mix looks better.

But perhaps I missed something--What happened to the original mixture, that involved the urine-be-gone or whatever it was called? Didn't it get the job done, work on paint, and have little adverse effects?

--Jack
 
'Urine Rescue' is actually 35% H2O2 solution, we just got used to using the chemical name, that's all.

'Oxy' is is still used.

We added xanthan gum to make a gel, in order to reduce the cost; immersing parts in a tank of liquid hydrogen peroxide costs a lot when the part is large, so we developed a gel to keep the volume of liquid down.

Glycerine or alcohol are added in small amounts to help the gum dissolve, that's all.

The original mix I use with the 'Oxy' doesn't damage paint, Lorne's hair bleach approach can attack some paints it seems; we really need more tests to confirm this.

At least there's two ways to get the job done now.......:mrgreen:
 
NOOOOOOOOOOOOOOOOO!!!!!

Bleach will only make the plastic go brittle; read the thread carefully as the formula is there.....

M
 
Lorne and I have worked with peroxide based bleaches, not chlorine based ones, bleach is a misleading term I suppose.

Using household bleach (which contains sodium hypochlorite BTW) may remove the yellowing in the short term, but it will make the plastic brittle and will discolour again over time as Chlorine is a halogen, just like Bromine.

Science bit over.
 
All I can find around here is 3%, that obviously isn't doin anything, I was thinking, what would happen if you boiled some of the water out of the peroxide? Would it make a stronger peroxide or totally ruin the mix?
 
I have been watching this thread for awhile now and have been hesitant to voice my opinion about the whole thing. First, the discovery of being able to remove that awful yellowing from aging plastic is great. I commend you guys for the time and expense of all the work you have done.

However I feel the safety aspect of using hydrogen peroxide has been downplayed. I have worked as a technician in the chemical industry since 1973 and seen first hand how dangerous some of these chemicals can be. To the average person, hydrogen peroxide isn't bad stuff. What you get at the pharmacy is 2% - 3% peroxide. You can put it on a cut or even rinse your mouth with it. The peroxide you get at a store selling hair care products is labeled as 10, 20 or 30 "volume". This is not the same as "percent". 20 volume is only 6% H2O2 and 30 volume is 9%.

The reality of hydrogen peroxide is that the higher the concentration, the more hazardous it becomes. 30% H2O2 is nasty stuff. If it comes in contact with certain chemicals (referred to as incompatibles) it will react violently. I don't know how people are obtaining this stuff. I was under the impression that chemical vendors would only sell this to someone that could prove they had a good working knowledge of chemistry.

To show the dangers associated with peroxide I will give you some real life experiences I have seen.

As an R&D technician a few years ago, our department was running some experiments with peroxide. Initially a Phd chemist was brought on board to do these experiments. He was in a lab at the far end of our building by himself. All the other chemists worked in one big room. I asked our group leader why he wasn't working with the rest of us and the reply was "he's running epoxidation reactions(peroxide reactions). If something goes wrong no one else will get hurt." Sure enough, an experiment detonated on him. He was OK because the setup was behind a shield.
Later that year I came on shift and was left an experiment where a chemist was trying to concentrate the peroxide content in an aqueous solution through distillation( this is the same thing that wmmullaney suggested in the last post). About 10 minutes later the setup detonated blowing shards of glass everywhere. I was lucky and was in an office about 5 feet way on the other side of the wall.
An incident occurred one day in our plant. They were using H2O2 to treat several hundred gallons of material in a tank. Previously, copper zinc oxide(an incompatible) had been used in the tank and had not been cleaned properly. As soon as the peroxide came in contact with the copper zinc oxide it reacted violently sending blue fireballs out the top of the tank. That was the last time hydrogen peroxide was used at the plant.
One of our chemists told me a story about an incident that occured when he was in college getting his doctorate degree. One of the students went to the basement to get a chemical out of a refrigerator. When he opened the door he discovered an old bottle of 95% hydrogen peroxide. He gently closed the door, went upstairs and called the bomb squad to come get it.
The stories go on and on.

My point in making this post is to show people that this material is not something to be played around with. It's potential for serious physical harm is great. Check the MSDS sheets for more information about the characteristics of this chemical and proper handling of it. Our member Lorne has been working closely with Merlin who is knowledgeable and can make suggestions about what chemicals can be used and what cannot. Always use chemical gloves and goggles and use only what has been spelled out by Merlin in the posts! I strongly suggest that no one does experimentation on their own!
 
I think those plastic face shields that cover your face should be used also. Lab coats are nice too. Both of those items are inexpensive and can be found anywhere.

http://www.fixandweld.com/images/SSP11.jpg

http://www.nixonmedical.com/assets/images/REDKP70WH_cuffed_lab_coat.jpg

The important thing is to read the MSDS beforehand to know what to do in case you do screw up and get some of the chemical on your clothes, skin, face, eyes, etc.

Also you need to know that if something does react with peroxide it will be an exothermic reaction (plenty of heat) so your plastic tub might soften/melt and release the chemical all over the place.

Oh, and keep this junk away from pets.
 
Thanks guys, wise words indeed.

In response to the comments about the strength of peroxide, my experiments were done using 35% (not volume), in order to test this under extreme conditions; if anybody's kit was going to be ruined, it was mine and I know how to handle these chemicals. If it was going to to bang, it would have on me, and nobody else. If I can thrash these ingredients up in a hand blender at a few hundred RPM, you can rest assured that the mixture is safe and there aren't any incompatibles. I am a chemist remember, I can't say the same for all of you closet alchemists out there; if you aren't sure of what you are doing or adding, don't add it, OK?

Now that the process has been proved, I would recommend that people use a lower strength grade, for the added safety factor it gives, at the expense of a little bit more time. The TAED we add as part of the 'Oxy' also makes some extra peroxide, due to the percarbonates and perborates added into the 'Oxy' ingredients.
 
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