The truth about Retr0brite – busting myths with science…

[Jeff_Birt]

The truth about Retr0brite – busting myths with science…
 

One of the situations we are often faced with when restoring an old computer is a yellowed plastic case. You have probably heard of Retr0Brite, few things in the retro community have caused as much controversy, rampant speculation and unfounded opinions as this subject. While there has been a lot of speculation and theories passionately bandied about on this subject there has not been an effort to understand the process.
 

A combination of research and practical experimentation was done to try and answer the questions: What it is Retr0Brite doing and what is it doing, or not doing, to the plastic. We will discover where color comes from, what plastic is, what makes plastic yellow, and what Retr0Brite is actually doing. This video is the result of an effort to get to the bottom of the matter using a scientific approach.
 

I ask that you please keep an open mind and watch through to the end of the video before banging out a comment on your keyboard. 
 

https://youtu.be/YPl356YKcVs

[DavidD]

Here's the link to the paper he references on the Youtube page.

https://onedrive.live.com/?authkey=!AHWTfrYkz_I8Ioo&id=FB359F9996BEF8D1!335256&cid=FB359F9996BEF8D1

 

The conclusion:

Quote

Conclusion - Yes, it is a bleaching process.

All of this experimentation and research has led me to the conclusion that Retr0Brite is after all a bleaching process. It exhibits all the characteristics of a bleaching process and in fact hydrogen peroxide is a well-known bleaching agent.

 

The addition of TAED, which forms PeraceticAcid, another bleaching agent that works better at lower temperatures,is move evidence that Retr0Brite is a bleaching process.

 

It is rather anticlimactic in a way to come to the conclusionthat all one is accomplishing is bleaching something back to its original color. It does not sound to exciting or technical. There is no magical new chemical process that is replacing lost hydrogen atoms, there is no ‘stabilization of bromine’, or any other fantastical operation happening.It is just like bleaching your socks.

 

Edited July 4, 2021 by DavidD
Extract of conclusion

[wierd_w]

It is important to mention that not all bleaching processes are created equally though.

 

Hydrogen peroxide bleaching uses chemically activated oxygen only, for instance.. Hypoclorite on the other hand, can form complexes with chlorine, where peroxide wont.

 

 

I am rather curious if it is just the strongly oxidizing environment jamming the plastic full of free electrons. Curious if just a strong negative ion bath would do the same thing. (one of those otherwise very dangerous "ionic breeze" air filter systems, attached to an extension cord, and placed inside a plastic bin containing the items.)

 

(as for the issues the experimenter suffered, concerning electrolysis-- He needs to invest in carbon electrodes.)

 

 

Edited July 4, 2021 by wierd_w

[+OLD CS1]

1 hour ago, wierd_w said:

I am rather curious if it is just the strongly oxidizing environment jamming the plastic full of free electrons. Curious if just a strong negative ion bath would do the same thing. (one of those otherwise very dangerous "ionic breeze" air filter systems, attached to an extension cord, and placed inside a plastic bin containing the items.)

Simple enough to test.  Build a voltage multiplier with an AC input, and either a fanned out carbon fiber cable for the output or a simple needle or a few.  Of course, you will need to content with the ozone this creates.

[Keatah]

1 hour ago, wierd_w said:

I am rather curious if it is just the strongly oxidizing environment jamming the plastic full of free electrons. Curious if just a strong negative ion bath would do the same thing. (one of those otherwise very dangerous "ionic breeze" air filter systems, attached to an extension cord, and placed inside a plastic bin containing the items.)

How is Ionic Breeze dangerous?

[wierd_w]

Production of ozone.

[Keatah]

Kinda thought so.

[Jeff_Birt]

7 hours ago, wierd_w said:

It is important to mention that not all bleaching processes are created equally though

 

(as for the issues the experimenter suffered, concerning electrolysis-- He needs to invest in carbon electrodes.)

 

 

Yes, I made the point in the video that the choice of the bleaching agent depends on the job at hand. Bleaching your socks is a different job than bleaching paper pulp. And yes, carbon electrodes would have been a big benefit. The electrolysis rig ran long enough to show that the exposure to the hydrogen or oxygen gas alone had no discernible effect.

[Jeff_Birt]

5 hours ago, wierd_w said:

Production of ozone.

Some folks have tried this and had no luck. I think the number of ions generated by an ozone making apparatus is orders of magnatude less than that which occurs from H2O2 decomposing.

[Tanooki]

14 hours ago, DavidD said:

Here's the link to the paper he references on the Youtube page.

https://onedrive.live.com/?authkey=!AHWTfrYkz_I8Ioo&id=FB359F9996BEF8D1!335256&cid=FB359F9996BEF8D1

 

The conclusion:

 

Thanks.  Seems someone complained about my post asking for a summary not forcing a youtube page view as it's gone.  I appreciate that.  I can't always watch videos, and only linking that is just forced.

 

I do like the chain of thought weird has going there.  De-funking stuff in such a manner has its own differing ways so just carpet calling it bleaching is a bit much.  Bleach has its way, retrobrite has its, the chlorine example he used was another.  It's curious, makes you wonder, if it were really tested, what is it exactly doing at the more base chemical/molecular level.  For all we know it may be de-uglying it, but also killing the material itself where it'll fall apart like holy cheese balsa wood brittleness 10 years after the fact.

[wierd_w]

The "Structural color" suggestion in the linked paper is an interesting prosepect.

 

There are two major ways that a substance gets a "color".  The first one, is light absorption, due to valence electron configuration. (electron configuration in the electron orbital structures the compound presents at its outermost valences.)  Differing electron configurations have different quanta of energy they can absorb or emit, and that includes the energy of incoming photons. The second one, involves microscopic structures that function as cages or traps for photons of different wavelengths. (see for instance, the "blue" and "Green" on peacock feathers.)   

 

 

The implication here, is that this is kindof the first kind, but also kind of the second kind also.

 

 

A plastic molecule is a long, convoluted thing that looks a bit like a section of cooked ramen noodle.  (well, usually anyway. there are exceptions. Some look more like lasagna noodles) These tend to be comprised of carbon or nitrogen bond skeletons, with hydrogen bonding points along the sides of the chain.  A good example of the first type, would be PET. (Poly Ethylene Terepthalate)

 

It has a diagram model like this:

and a molecular representation like this:

 

 

An important thing to remember, is that bond angle is conserved with bond energy, due to VSEPR theory.

 

 

In the above example, the backbone is held together by oxygen atoms, that are themselves stuck to aromatic benzene rings, and to ethylene monomers.  Looking at this molecule, it should be vulnerable to UV light (which would help knock electrons off that hold the chain together at the oxygen bond points), and should be vulnerable to strong acids (through hydrolysis reactions, again on the oxygen atoms).  The little cis-trans double-bonded oxygen atoms at either side of the benzene ring allow the formation of hydrogen bonds (by incorporating ambient water vapor) between the chains, so that they lock together more or less tightly into more or less flat sheets.

 

 

An example of the second type, would be something like Aramid plastic. (Things like nylon, kevlar, etc.)

 

Those form dense sheets, through strong hydrogen bonding between chains, and are a nitrogen chain type polymer.

 

The inter-chain hydrogen bonds are illustrated with the ... between the Oxygen and Hydrogen atoms at cis-trans locations on the chain.

 

 

The one we are probably most concerned with is ABS though.  (Acrylononitrile butadiene styrene)

It is a tri-polymer, comprised of three different monomers: Acrylonitrile, Butadiene, and Styrene. 

 

 

A couple of things could happen here.  1, the double bond on the butadiene monomer could get oxidized, which will change the bond angle, and thus result in both structural color change, reduction in polymer strength, and change in outer valence configuration (and thus differences in photon absorption) of the resulting molecule. 

 

It might be possible that ripping the likely "suddenly attached hydrogen" that would happen if that became a single bond (something has to satisfy the bond energy there, and that something is usually hydrogen when it comes to carbon bonds) off, (such as with a strong negative ion bath, or a strongly oxidizing environment with lots of charged oxygen) would force the molecule to regain a double bond there, restoring the polymer's original chain structure. HOWEVER-- the total chain would also be at risk for hydrolysis reactions, that would break apart the chain, and thus lead to the "crumbling, cracking, brittleness" you are describing.

 

I would suggest a more radical set of experiments in a laboratory using small test granules, and an atomic force microscope, where a sample of yellowed ABS is exposed to vacuum chamber straight UV light, and measured (before and after exposure) with the AFM, to see how the structure changes, then again with retrobrite.

 

 

I am curious if a combination of UV light (to help break that bound hydrogen off), combined with a strong negative ion bath (ozone ions), would do the trick, by liberating that hydrogen (to form water vapor + oxygen), and forcing a double-bond to form again.  It would run the risk of oxidizing the rest of the chain though. (breaking the carbon-carbon bonds probably requires less energy than the carbon-hydrogen bond we are targeting.  Doing this a lower temperatures would help control this.)

 

(Note, I am not actually a polymer chemist. I just remember my college chemistry class.)

 

 

This paper suggests that the degradation that occurs happens at the butadiene monomer component, which is where I also suspected.

 

They suggest that during thermal forming, peroxides form suspended in the molten plastic charge, then then serve as catalysts in the degradation of the plastic under UV irradiation.

 

 

 

 

 

 

 

 

 

Edited July 4, 2021 by wierd_w

[Tanooki]

@wierd_w Thanks.  I'm no biochemist so I could never have dug around enough to put that together so well.  Yes that's basically reading what you put there is where my thought were going on the potential circumstance of having a brittleness hit the plastic due to the process being involved in whatever retrobrite really could be doing here.  Bleaching by it's basic household knowledge is effectively a chemical that meets color and shreds it's essence away restoring the formerly white product, whether it's the stain, or the stain and any factory(or home) dyes applied to said surface.  Basically another way, much like bleaching someones a hair too long sucks the color out entirely and leaves it damn near white if it's in long enough, even does it to the skin too which is why people end up using gloves.  It tears the very pigment off stuff, and that ripping could be creating a situation of progressive brittleness where is breaks down the very original strong bonds of the ABS plastic basically leaving many microscopic holes you can't see like a teen sponge.

 

I like the idea of some real controlled tests, it would be fantastic to know what damage or not that really is doing for a short(or long?) term bleaching effect to restore the pretty look of the original product.

[Jeff_Birt]

8 hours ago, Tanooki said:

I do like the chain of thought weird has going there.  De-funking stuff in such a manner has its own differing ways so just carpet calling it bleaching is a bit much.  Bleach has its way, retrobrite has its, the chlorine example he used was another.  It's curious, makes you wonder, if it were really tested, what is it exactly doing at the more base chemical/molecular level.  For all we know it may be de-uglying it, but also killing the material itself where it'll fall apart like holy cheese balsa wood brittleness 10 years after the fact.

Well, here is the rub; if you actually watch the video or read the paper you know why that conclusion was reached. There is nothing magical about bleaching it is a well understood chemical process that alters the atomic bonds in the molecules. Again, watch the video and you would have learned that too...

[Jeff_Birt]

2 minutes ago, Tanooki said:

@wierd_w Thanks.  I'm no biochemist so I could never have dug around enough to put that together so well.  Yes that's basically reading what you put there is where my thought were going on the potential circumstance of having a brittleness hit the plastic due to the process being involved in whatever retrobrite really could be doing here.  Bleaching by it's basic household knowledge is effectively a chemical that meets color and shreds it's essence away restoring the formerly white product, whether it's the stain, or the stain and any factory(or home) dyes applied to said surface. 

Bleaching does not 'shred its essence away', it changes double atomic bonds into single bonds, altering the 'shape' of the chromophore altering the wavelengths of light if reflects therefor changing its color. Again, gone into in great detail in the video. Please don't create more myths.

The effect on human hair by bleaching is a different subject.

[wierd_w]

Human hair has superficial similarities to aramid plastics, in that it too is comprised principally of a polyamide group.  Hair is naturally colorless. (white).  It is the presence of a larger organic molecule that is able to shift and move around its valence electrons (melanin) that gives the hair its color, in combination with the mechanical distributions of that molecule inside the hair shaft.

 

Most hair shafts are hollow inside, and that hollow shaft tends to be where the melanin gets most heavily concentrated.  Peroxide bleaches make small holes that penetrate into this hair shaft, and that process is facilitated by the ammonia based compounds found in most commercial hair dyes, or commercial permanent kits.  The peroxide then oxidizes the melanin inside, making it unable to perform its usual function, (and also turning it from dark brown/practically black, to a straw color).

 

 

In this case, we are changing the bond angle of the butadiene monomer component, by attempting to rip that hydrogen off, using chemically activated oxygen. 

 

This corresponds to the two equally accurate descriptions of what Reduction/Oxidation reactions do.

 

Oxidation reaction either removes hydrogen, or adds oxygen.

 

Reduction reaction either adds hydrogen, or removes oxygen.

 

In this case, (ABS + Retr0Brite + UV light), it appears we are removing hydrogen. 

 

 

Since we are removing hydrogen, it would make sense to try and better control the reaction to avoid breaking bonds in places we do not want them to be broken. (Since doing so, is what will result in short chain defects, resulting in spalling, cracking, and embrittlement of the plastic.) The best ways to do that is to control the temperature, control the wavelength of the UV light so that it is more specific for that bond configuration (specificity of absorption, due to the different valence energy of the carbon-hydrogen bond, vs the carbon-carbon bonds), and control the stoichochemistry of the surrounding ion bath (only sufficient excited oxygen to perform the desired reaction, and not more or less.)

 

An idealized process could be devised with better understanding of the chemistry involved.

[Tanooki]

Birt I get you're being salty with the air quotes and the rest because I wouldn't watch your video, but after years of people spamming their pages on here and other forums, I just don't bother anymore, even in the cases where I can actually have the time to watch.  I didn't then, but the snark wasn't needed so well, yeah, not watching it.  It's rude to pop into a forum and just try and grab views and subs going hey check my video.  I thought AA actually had or did at one point a thread for people just pushing their videos to curtail that.

 

 

Wierd, so it's superficial at best, may work for a basic comparison but nothing more.  The idea of porousness in either case of the hair or plastics, the addition of the other agent to cause the change makes sense.  While I'll admit at a low level I wouldn't get it as I didn't do chemistry in college, at a high level I'd find it fascinating to read up some solid proof of whatever is actually going on.  Far too long people have just said retrobrite it and that's that, a few coming back years later talking about discoloration creep again, but in the most cases not.  What's going on, what maybe went on again that re-caused the issue.

[wierd_w]

The research paper i linked the abstract to suggests that moisture, or other hydrolisis promoting compounds are present in the molten plastic when it gets injection molded. Those substances then react with the UV light, and become reactive. Further UV exposure, in the presense of those now reactive compounds promotes a reduction reaction, in which the carbon double bond in the butadiene is hydrogenated. (Becomes a single bond, and a hydrogen becomes attached).  This alters the bond angle, and changes the light absorption properties of the plastic, as well as weakening it.

 

Hydrogenation is a form of reduction reaction.

 

From what i can tell, retrobrite tries to reverse the reaction, by pulling that added hydrogen off, and causing the double bond to reform.  That process requires energy and a catalyst, or a reactant..  Retrobrite uses a UV light source and heat as the energy source, and reactive oxygen species as the reactant.

 

What i said prior, is that we want precise application of where the energy gets applied.  Different bonds between atoms have different valences on those atoms filled, and that changes the light frequencies they can absorb.  By precisely controlling the KIND of UV, (what frequency band) we can target the hydrogen atom at that bond point and blast it off, without attacking the other bonds in the plastic (because they cannot absorb the light, and so the energy needed to break them apart is not available).  Heat would be undesirable as an energy source because it would affect the whole molucule without that specificity.