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Thread: Removing yellowing from plastics - Part 2

  1. #1

    Default Removing yellowing from plastics - Part 2

    The original thread is over 200 posts long now and getting to be a heavy read for some, so Lorne and I thought it was best that we start a new thread here, with a "Story So Far" summary, before we start more experiments.

    So, what has been discovered and learned so far?

    1. We have learned that a magic concoction has been created that can reverse the years of yellowing of plastics, caused by the brominated flame retardants (which were added to the plastic when it was a masterbatch) migrating to the surface of the plastic and attracting oxygen molecules which become attached by a co-ordinate bond.

    2. Bromine molecules are susceptible to ultra-violet light, in that chemical bonds involving bromine molecules can become destabilised if irradiated by UV light. This is what we are exploiting to remove the oxygen molecule from the brominated flame retardant.

    3. The yellowing can be reversed to a degree by immersing parts in hydrogen peroxide or "Oxy" on their own, however, on their own they don't do that much; what is needed is a chemical called TAED (tetra acetyl ethylene diamine), which is a chemical found in the "Oxy" type laundry boosters. Why is this useful? It's useful because it catalyses perborates and percarbonates in the "Oxy" to produce peroxides; it can also catalyse hydrogen peroxide, which is exactly what we want. This is what makes the mixture much more potent.

    4. The optimum mixture and conditions for reversing yellowing of plastics seems to be the following:-

    A) Hydrogen peroxide solution, the strongest you can lay hands on;
    B) UV light, either as sunlight or a UV lamp;
    C) Approx 1/4 teaspoonful per gallon of "Oxy" laundry booster.

    Parts immersed in this mixture will have the yellowing reversed in six to eight hours on average. Severe yellowing may take longer but it will only be a matter of a day or two. The mixture once made will last about four days before all of the peroxide is spent.

    5. A more recent development is that the mixture can be made into a gel. Initial tests with Xanthan Gum added to the original mixture have shown that it can be made into a thicker material which can be brushed onto surfaces. This mixture foams up but still removes the yellowing when put under UV light, and can remove yellowing in four to six hours. This method also drastically cuts down on the amount of liquid required and means large areas can be treated at a relatively low cost. Other thickeners such as corn starch, hydroxy ethyl cellulose, wallpaper paste, latex or similar inert thickener may also work, however, tests are in the early stages, feel free to try some of these and report back if they work.

    6. Recent tests by Lorne have shown that powdered hair bleach and hydrogen peroxide solution can give a similar effect to the original "Oxy" mixture, however, there may be side effects associated with using this material; early tests have seen adverse effects on paint and stickers may also be affected by this product. The original "Oxy" mixture does not affect paint or stickers, unless the stickers are held on with a water based glue or are paper stickers.

    7. If you are planning to do this in a hot climate, please be aware that this mixture will heat up during the day. Lorne is in Arizona and found that temperatures in excess of 100F (38C) and beyond were encountered, which caused some warping and distortion of large pieces. If this is the case where you live, always add the component to a cold mixture and check the temperature during the day.

    We will add to this original post in the thread as we learn more. If you wish to read the original thread, it's here:-

    http://www.vintage-computer.com/vcfo...ad.php?t=11877

    The story continues.........
    Last edited by Merlin; October 7th, 2008 at 11:05 PM.

  2. #2
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    @ Merlin
    Well done.
    You might want to edit that first post, to add a link to the part 1 thread, in case someone stumbles across this new post and wants to delve further into what we've learned.

    Now, with regard to the last post in Part 1, I think the Umpire blew the call by calling a Strike before the ball even reached the plate. (It's not a Home Run, but it's at least a Ball).

    Here's the lastest (drastic) results - done in three hours this morning:

    I think this is a good start for this new thread.
    (The Televideo was originally black and white).

    Before:
    Televideo 925 - before.jpg
    Gutted and ready to go:
    Televideo 925 - gutted.jpg
    Keyboard before:
    TV925 keyboard - before.jpg
    Keyboard done:
    Televideo 925 - keyboard done.jpg
    For comparison (processing the balance of the case will be done in the next week):
    Televideo 925 - keyboard done & case.jpg

  3. #3
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    Sep 2008
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    Columbia, SC USA area
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    @ Lorne

    Awesome results! Is that with the Xanthan Gum mix?
    Cheers!
    Wmmullaney

    Collection: Replica I TE, 3 Apple IIe, Apple IIgs, Apple Performa 630cd 68k, 4 PowerPC Performa, 2 Timex/Sinclair 1000 and 1500, PC/AT c286 clone, Commodore 64 and 128, NCR box with a 386 mobo, TRS-80 PC-2, DreamCast, PlayStation 1 and 2, 2 iMac G4, Powermac G3 beige and aqua, Twinhead 386, Toshiba T1910, Zenith zwl-183, set of Intel MCS-8 boards (CPU, RAM, ROM, I/O)

  4. #4
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    Quote Originally Posted by wmmullaney View Post
    @ Lorne

    Awesome results! Is that with the Xanthan Gum mix?
    Nope - this was with the "Strike" powdered bleach mix. It's sticks real good to the verticals which is what I'll need, to do the rest of the case.
    We'll work on the XG mix to see if we can't thinken it up and make it stickier.
    (The PB mix smells much better than the XG mix though)
    Last edited by Lorne; October 7th, 2008 at 01:56 PM.

  5. #5

    Default

    Wow. I shoud realy considering doing this with my Amiga 500. It looks like it has been in the sun for YEARS (it is nearly plain yellow with a hint of grey).

    However, I neither got the time or oppertunity to do it, because of homework, ain't old enough (16 years) to handle the kind of chemicals used, ech...
    Last edited by per; October 7th, 2008 at 01:44 PM.

  6. #6
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    Columbia, SC USA area
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    I need to watch this thread closer Need to do something like that to my poor little IIe.
    Cheers!
    Wmmullaney

    Collection: Replica I TE, 3 Apple IIe, Apple IIgs, Apple Performa 630cd 68k, 4 PowerPC Performa, 2 Timex/Sinclair 1000 and 1500, PC/AT c286 clone, Commodore 64 and 128, NCR box with a 386 mobo, TRS-80 PC-2, DreamCast, PlayStation 1 and 2, 2 iMac G4, Powermac G3 beige and aqua, Twinhead 386, Toshiba T1910, Zenith zwl-183, set of Intel MCS-8 boards (CPU, RAM, ROM, I/O)

  7. #7
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    VERY impressive work, guys.... very impressive...
    Just what I needed - something ELSE to consume my free time

    T

  8. #8
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    Quote Originally Posted by Sharkonwheels View Post
    VERY impressive work, guys.... very impressive...
    Just what I needed - something ELSE to consume my free time

    T
    You have free time? What's it like?

    I seem to recall the term, vaguely, sorta like something called "vacation"
    Legacy Computers and Parts

    Sales of, parts for, and repairs to, Vintage and Legacy computers.

  9. #9
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    Quote Originally Posted by per View Post
    Wow. I shoud realy considering doing this with my Amiga 500. It looks like it has been in the sun for YEARS (it is nearly plain yellow with a hint of grey).

    However, I neither got the time or oppertunity to do it, because of homework, ain't old enough (16 years) to handle the kind of chemicals used, ech...
    Hey, I didn't know there was another 16 year old on the forum! I'll have to remember that. Granted we aren't old enough to handle that stuff, the internet is a wonderful thing and knows no age. That, or have an older family member get the for you.

    So far so great on this de-yellowing stuff. I'll the people who said you cant do it will have to eat their words with a fork and spoon! May not be of much help, but try either boosting the XG in the mixture or adding a thickening agent--like flour.

    --Jack
    Come to the dark side...we have cookies.
    Wanted: Somebody to buy alot of my stuff
    AT&T PC 6300 site

  10. #10

    Default

    @ Yzzerdd

    That is exactly the current thinking, I am going to try some experiments with Xanthan Gum this weekend. I've got some Kelzan D and also some hydroxy ethyl cellulose to play with. I think the problem with the XG is getting it to disperse as it can be difficult to mix in and can go like semolina; a small amount of glycol or glycerine may help. I'll know more once I've done some kitchen chemistry .

    Wallpaper paste is actually starch, which is something I will also try out to see if it works.

    @ Lorne

    I am a bit concerned about the effect the hair bleach had on the black component you tested and also the keys on the keyboard as pictured above (assuming you treated the keys). The 'bloom' on the dark plastic suggests that some kind of chemical attack on the surface has occurred, the effect you saw on paint isn't good either, escpecially for those with screen printed logos on cases, keyboards etc. We'll need to watch out for this going forwards. It doesn't happen with the original mix, so my educated guess is that it's the solvents in the hair bleach causing this.
    Last edited by Merlin; October 8th, 2008 at 12:42 PM.

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