Thread: Epoxy CPR

The chemical combinations in epoxy resin aren't necessary to know and you can't get them at the local hardware store anyway.

The Glycol groups in the epoxy will crystallize when exposed to freezing temperatures. This is normal and sitting the container in a bath of warm water will restore the resin no matter how bad it's gotten.

Epoxy does have a shelf life, which according to most formulators is about a year. This said I've used epoxy that was several years old and it worked fine, though I didn't test it and didn't use it on highly loaded parts.

If you have old, crystallized epoxy, warm it (I've used the micro wave more then once). Steel containers can affect hardener more then anything else. It'll turn red and it contaminates the hardener too. Again, I've used old epoxy, in steel containers and it's worked, but if more then a couple years old, I wouldn't trust it to hold your keel on.

but I don't think I can use all the resin before it becomes useless.

What makes you think it will become useless?

Originally Posted by PAR

The chemical combinations in epoxy resin aren't necessary to know and you can't get them at the local hardware store anyway.

I know but as a nosey chemist (analytical not adhesive)... one component has a melting point of 122C so something has to make it mobile

Originally Posted by PAR

What makes you think it will become useless?

I have a 2 litre container that is completely solid and didn't think I could revive it, didn't want the same to happen to another container however seems like they can be revived with a bit of warmth.

thanks

Tor what brand epoxy are you using? (Us labrats are nosey too).

Hell. I didn't know epoxy can go off.

I have bought a 30L pack of BoteCote for our Hartley which has taken us 18 months so far and will probably take another 2-3 years to finish.

I hope I haven't wasted my money. That stuff is not cheap!

Originally Posted by Tor

I know but as a nosey chemist (analytical not adhesive)... one component has a melting point of 122C so something has to make it mobile

I have a 2 litre container that is completely solid and didn't think I could revive it, didn't want the same to happen to another container however seems like they can be revived with a bit of warmth.

thanks

Might help ... I don't really think it is a melting problem - I believe it is solvent/solute behaviour.

My understanding is that epoxy is close to a supersaturated solution. So if some of the more volatile components evaporate off then then it passes the supersaturated point.

Another thing that can cause it is like hot tea taking more dissolved sugar and cold tea taking less, if the epoxy (typically the resin component) experiences a temperature drop then some of the dissolved materials will come out of solution.

Warming then restores it to liquid by redissolving the crystallised ingredients that have "come out of solution".

Because of the energy curves once redissolved with heat it will remain liquid for quite a long time.

However a prolonged temperature drop may mean that less of the dissolved materials can again drop out of solution.

Like PAR I've used epoxy that is much older than a year - I think this is quite a conservative figure - after seeing thousands of boats launched by home builders over lots of years there have been very few failures indeed - even though I know the patterns of home boatbuilders well and most would be using epoxy that is more than a year old for part of their build.

If I was building a boat that was taking design right to its limits - a real out and out raceboat, I would probably suggest ordering new epoxy for the job.

It is easy to mix a bit to see if the epoxy goes off. My feeling for my own building is if it is more than three years old I would be keeping it away from high stressed components - of which there are only a few in my boats - really only the mast step and partner and the mast.

Best wishes
Michael Storer

Mik's comments about resin age are pretty much what I think as well. Assuming a 3:1 margin, 3 years is likely safe for highly loaded parts, but I'm not going to build a carbon spar out of it and "find out".

Epoxy is (typically) an acetone reacted phenyl, (given some electricity and pressure) which produces Bisphenyl A (a couple of phenyl groups and acetone). Unattached acetone and some phenyl is knocked off the Bisphenyl A molecule and epicholorohydrin is introduced (activation) and a couple of glycol groups get placed on the end of the bisphenyl A molecule. The resulting reaction cures into Diglycidol ether of bisphenyl A.

You had to ask. BTW this is the shortest description of what epoxy is I've ever managed.

PAR

A lovely concise description of epoxy...

BoatMik,

Yep that's what I've concluded

labr@

Botecote

Good value and good service

All

Thanks for the feedback. The resin appears to be able to be brought back from the brink, I don't think I'll push the design issue as I'm building canoes/yaks and I'm too lazy to paddle that fast and not brave enough for white water.

cheers

Bote cote epoxy has no solvent whatsoever, if you want to reconstitute your crystallized epoxy all you need to do is either make a hot box or stick it in the bath tub/sink with hot water straight from the tap just ensure you dry the outside of the containers after this, hope this helps