Any suggestions for degassing epoxy floor coating?

[bob_mp]

Hi,
I'll be putting down the epoxy color coat in my garage late this afternoon. Last time, I ended up with lots of bubbles, perhaps due to air getting entrained in the epoxy during mixing. I probably should have waited until later in the afternoon as well. I have no reason to think that the product itself had anything to do with the problem.

A friend, former Professor of Chemistry, suggested degassing it the epoxy. After watching some YouTube videos, here's the plan:

I've got a 2 stage, 7 CFM vacuum pump, a 40 quart vacuum chamber, and a bunch of paint buckets. I'm planning on mixing the epoxy thoroughly, air be damned, in small batches (1-2 gallons) and then degassing it for 4-5 minutes after it burps. This will bring it to a good rolling boil under vacuum.

Anyone have any experience doing this? Any suggestions?

Any worry about changing the chemistry by letting it boil under a vacuum (boiling out the solvents, for example)?

I'll let you guys know how it turns out.

Thanks!
Bob

 

[Interex]

Isn't out gassing from the concrete itself? Maybe I misunderstood the term when I heard it long ago.

 

[bob_mp]

You are correct, there is outgassing of water vapor from the slab. What I was referring to is removing air from the epoxy coating mix along the following lines:

Cheers,
Bob

 

[Shea]

A caution flag goes up on this for me. If you mix your epoxy properly, apply it in ribbon on the floor immediately after mixing, spread it out with a squeegee and then backroll with a good quality roller, you shouldn't have any issues with bubbles. This is discounting of course out gassing of the concrete.

That said, if you are using 100% solids epoxy, you will have very little if any solvents in the mix. If you aren't using 100% epoxy, removing solvents may cause a couple of problems. The first is the ease of application. Many companies use solvents or water as a carrier agent to make the epoxy go on smooth like paint so that it is an easier process for a DIY person. It's also important for the penetration of the product into the concrete. The second is that is may speed up the curing process and make it difficult to spread.

Another thing to consider is that when mixing 100% solids epoxy, you need to get it out of the bucket as soon as you can or it will increase in temperature due to the thermo reactions of the epoxy and start to cook in the bucket. Leaving it in the bucket for 5 minutes after mixing it is not a good idea.

I admit it's a novel idea, but I would definitely call the manufacturer before attempting it.

 

[bob_mp]

An update

It's better, but there are still some bubbles. Hopefully they will lay down tonight.

It seems to work well for small batches -- something like half a gallon works very well. The epoxy flooring expands a LOT -- close to 10:1. In the smaller batches, I could get it to burp and lay down in 6-7 minutes and it didn't get too hot. Zero bubbles on that batch.

Then we started on larger batches -- very different animal. With the larger batches, I need to bleed the vacuum to prevent overflow, and this slows down the process. The thing you are working against is time. The lack of convection cooling results in the larger batches getting (really) hot and this stokes the reaction.

Big batches are difficult -- the CFM of the pump, the volume of the chamber, and heat all conspire against you.

It might also be that I am sucking out solvents that inhibit the reaction or improve workability. My painter was telling me that the stuff was sticky. Degassing definitely seemed to speed up the reaction.

Tomorrow, I'll put down the clear coat. It's alleged to have a longer pot life.

I'll post up some pics tomorrow of the finished result.

Cheers,
Bob

 

[LegacyIndustrial]

Bob:

This sounds interesting.
There are several things that can cause this...

Very open, porous concrete being coated with a viscous 100% solids epoxy.
Prime out-gassing candidate, no matter what temp. Can be avoided by using a primer.

High-Speed mixing, introduces air bubbles, they try to escape during cure.
Very common, can be "porcupine rolled" to release these bubbles.

Moisture in concrete, releasing on a hot day or present for other reasons.
Coat in the evening as the temp is dropping. Perhaps consider a negative side waterproofing coat.

If you use a low-speed drill for mixing you should not have issues with air-bubbles and no need to remove them but your pump sounds like fun!

 

[bob_mp]

Thanks Scotty for the feedback.

I don't know what to make of mixing and what high speed is. I had my drill on low -- does this count (jk)?

Can you educate me on "porcupine" rolling?

For the smalller batches, the mix burped and laid down (and boiled) beautifully. With the larger batches, I didn't have enough time or chamber to flatten it. I think I need more pump; I definitely need more chamber.

I did notice the following -- the pump, working against an empty chamber, pulls down to 29 mm in a big hurry. With the epoxy in there. it's much more slow (hopefully a good thing).

Pics to follow tomorrow.

Cheers,
Bob

 

[Shea]

Bob, porcupine rollers are used to relieve surface tension when rolling epoxy. They help to eliminate any bubbles caused by out gassing or mixing. I liked using them when rolling on primers and for humid days. Just google "18" porcupine rollers".

 

[bob_mp]

Hi Shea,
Thanks for the pointer. I wasn't aware of these -- the manufacturer recommended a different type of roller; which are conventional and designed for epoxy. I think this might be the trick. If I ever do this again, I will get one.

The epoxy coat bubbled up last night as before, though not as much as before. The bubbles were much smaller and less dense. Still not a happy thing.

This morning we resanded the whole garage and wiped with alcohol. This evening,we put down the clear coat with the micro glass beads in it, which I degassed.

This went really well. The clear coat responded really well to the vacuum chamber. It burped quickly (about 90 seconds) and didn't have the same exothermic kick. It expanded to 10x the original volume and then collapsed. It came out like glass, wasn't very hot, and went down really smooth. No bubbles so far.

I am cautiously optimistic -- if tomorrow it looks like it did this evening, I am totally psyched.

Bob