What category of compound is this?

[strangerep]

I'm researching a product known as EzyEpoxy Grout, which is marketed as being superior to conventional epoxy grouts that tend to go yellow over time. EzyEpoxy does not go yellow (which I've verified by conducting a long experiment).

EzyEpoxy is a 2-part product mixed from a 2-cartridge gun. After a while it hardens to a rubbery consistency (and can be trimmed from surrounding tiles by blade) but later becomes rock-hard.

I'm curious what category of compound it really is.

The MSDS can be downloaded here. Key ingredients seem to involve cyclohexylamine, a polyoxy-aminomethylethoxy, silicon dioxide, sulfuric acid, and benzyl alcohol (which I'm guessing is used as a solvent?), which I list below:

EzyEpoxy Hazardous Components:

20%: 2,2'-dimethyl-4,4'methylenebis(cyclohexylamine)
10%: Poly[oxy(methyl-1,2-ethanediyl)], .alpha.-(2- aminomethylethyl)-.omega.-(2-aminomethylethoxy)-
5%: Benzyl alcohol
5%: Quartz (SiO2)
4.5% Sulfuric acid, barium salt (1:1)

(The non-hazardous components are not listed, so I'm unsure whether any of them are important in the hardening reaction.)

These compounds look VERY different from conventional epoxy constituents -- more like a 2-pack polyurethane(?) or even a hard variety of 2-part silicone? I done a little reading on Wikipedia, but it quickly exceeds my limited knowledge of chemistry.

So,... what broad category of compound is appropriate to describe this product?

 

[jedishrfu]

I couldn't find a direct answer to your question but felt you might be interested in this article about epoxy grouts pros and cons:

https://www.sciencedirect.com/topics/engineering/epoxy-grout

 

[strangerep]

I couldn't find a direct answer to your question but felt you might be interested in this article about epoxy grouts pros and cons:

https://www.sciencedirect.com/topics/engineering/epoxy-grout

Thanks, but unfortunately it seems to be behind a paywall.

I've used Mapei epoxy grout to tile a bathroom (travertine-look/beige porcelain, with beige epoxy grout), and a bedroom (marble-look porcelain, with white grout). The mechanical and mold-resistance properties of the epoxy grouts are great, but the now-yellow grout in the bedroom is very disappointing. The bathroom is ok -- even though it's yellowed a bit more than the original beige it still looks fine.

Over the past 10 months, I've been observing an experiment using the newer EzyEpoxy which is claimed not to yellow. Afaict, it has indeed retained its original brilliant gloss white colour.

FYI, my question arose from another thread I started last year here.

 

[jedishrfu]

That’s odd. I can see it at home. Maybe it’s country walled.

The article had info on grout tensile strength vs concrete tensile strength and expansion rates of both materials. It had some pros and cons related to discoloring too.

 

[TeethWhitener]

I'm pretty sure the MSDS is just listing the polymer as the developed (uncured) polymer, derived from the epoxide starting monomer. It's not a silicone (no silicon) and it's not a polyurethane (no amide). The structure is a polyethylene glycol (PEG) derivative:

The PEG structure is typical of polymerized epoxides. The diamine is the curing (crosslinking) agent. If I had to guess, I'd say the rest of the active ingredients are preservatives: benzyl alcohol is probably some sort of stabilizer (maybe a radical scavenger), the quartz is probably a dessicant, and the barium hydrosulfate is probably a buffer.

 

[strangerep]

The structure is a polyethylene glycol (PEG) derivative: [...]

Thanks. So I guess this is what Wikipedia calls a "polyol" on its polyurethane page (which seems to cover a vast range of compounds -- but also says it "needs attention from an expert in chemistry").

 

[TeethWhitener]

A polyol is a simply a compound with multiple hydroxyl groups. It’s not necessarily a polymer. Ethylene glycol is a diol (two hydroxyl groups), and is one of the simplest polyols. The suffix -ol just denotes the presence of a hydroxyl functional group (-OH).

Polyurethanes are generally made by reacting a polyol (like ethylene glycol) with a diisocyanate. PEG is a condensation (loss of H₂O) product of ethylene glycol. Probably confusingly for the non-chemist, poly(ethylene glycol) is a polymer with no hydroxyl groups (except at the ends of the polymer chains) which is itself made up of monomers that are non-polymeric polyols. Polymer nomenclature is tricky.

 

[strangerep]

Probably confusingly for the non-chemist, [...]

Yes indeed. I think I'd better stick to maths and physics.

Thanks again.

 

[DaveC426913]

Thanks, but unfortunately it seems to be behind a paywall.

That’s odd. I can see it at home. Maybe it’s country walled.

Is it possible y'both are describing the same thing but with different expectations?

I see a page that's about 15 screens long and full of info, but in the form of what appear to be excerpts from some book, which you can buy.

 

[jedishrfu]

Yes that’s what I saw, the info though was somewhat useful with pros and cons of epoxies, and various tensile strength numbers.

 

[chemisttree]

A polyol is a simply a compound with multiple hydroxyl groups. It’s not necessarily a polymer. Ethylene glycol is a diol (two hydroxyl groups), and is one of the simplest polyols. The suffix -ol just denotes the presence of a hydroxyl functional group (-OH).

Polyurethanes are generally made by reacting a polyol (like ethylene glycol) with a diisocyanate. PEG is a condensation (loss of H₂O) product of ethylene glycol. Probably confusingly for the non-chemist, poly(ethylene glycol) is a polymer with no hydroxyl groups (except at the ends of the polymer chains) which is itself made up of monomers that are non-polymeric polyols. Polymer nomenclature is tricky.

I don’t think anyone would call this a derivative of PEG. Perhaps PPG but not some version or derivative of PEG. This, however, is clearly polypropylene oxide with amine terminations. That’s only the resin part of this product. The active epoxide isn’t listed. The percentages only add up to 45%! The other 55% is described as “non-hazardous” but I’m sure it’s the reactive part of the system. Likely diglycidyl ether... reactive diluent.

There is a slower reaction that continues the hardening process after the initial gel (rubbery) stage. Not sure of all the reactions going on but you have difunctional primary and secondary amines in the mix with some epoxy group that isn’t listed in the MSDS. Lotta stuff going on. Benzyl alcohol is also used as a thinner and a solvent for the amine hardener, which might not be soluble in the epoxy resin/reactive mixture.

PEG is usually made from ethylene oxide AND ethylene glycol, not a condensation of ethylene glycol itself. The monomer is ethylene oxide not ethylene glycol.

 

[strangerep]

[...lots of interesting stuff...]

And for extra credit...

What is your educated guess about whether the cured EzyEpoxy compound will eventually suffer yellowing and, if so, how long it might take?

 

[chemisttree]

There is nothing listed that is special in that regard. I’ll bet the magic is in the other part of the system. Likely a UV stabilizer.

 

[strangerep]

There is nothing listed that is special in that regard. I’ll bet the magic is in the other part of the system. Likely a UV stabilizer.

Hmm, I guess I should try to read up on that a bit more...

What are some examples of UV stabilizers? Do they give unlimited UV immunity, or just partial/temporary protection?

 

[chemisttree]

Hmm, I guess I should try to read up on that a bit more...

What are some examples of UV stabilizers? Do they give unlimited UV immunity, or just partial/temporary protection?

Read more here. UV stabilizers are like sun block for the product. Good Google term, “UV stabilizers epoxy”

 

[strangerep]

Read more here. [...]

Thanks.

Next question: what about yellowing that is not caused by UV? I.e., slow spontaneous long term changes to the cured epoxy molecular structure, even in the dark? I read about HALS in that article you linked but is that still relevant for yellowing that occurs regardless of the light level?

 

[chemisttree]

Yellowing is also caused by high temps and oxygen. Anything that might interfere with or react with the UV stabilizer or HALS compound will also lead to yellowing if exposed to the light. Anything that could generate free radicals, whether in the light or in the dark, causes it. So, oxygen is on the list I suppose.
Free radical scavengers might interrupt that process but you would need one that is colorless... kinda difficult but not impossible I suppose.
HALS are free radical scavengers so it would work for any process that involves free radicals in the dark as well.