Shelf life of epoxy?

[MuddyFeet]

I have some epoxy left over from a major boat building project. It's about 8 years old and always been stored in the basement. I dip into it now and then for small projects on the boats or around the house.

I'm rebuilding a centerboard trunk this winter -- a little more involved than the odd repair job. Should I buy "fresh" epoxy? I'd hate to have the project not turn out well because I used "old" epoxy.

I have nothing to base my concerns on, just wondering. A search of old threads didn't offer any insight...

Thoughts?

[DanO]

I've just used 2 year old epoxy (System 3) on a mahogany glued/bronze drifted transom. I seem to recall something in the literature about epoxy having a limited shelf life of a year or so, but mine seems solid as a rock. The only problem I noticed was that the working time was cut pretty short. Seemed to heat up and solidify pretty quickly. All in all I wasn't that worried since the transom is drifted together and if the epoxy fails, I figure I could always rout the seams and reglue.

I'm not sure about using 8 year old epoxy, though. I'd call the manufacturer for advice(they'll probably tell you to buy more in any event!)

Dan

[JimConlin]

IIRC, the word on this subject from the Gougeons was:
Over time, resin gets thicker.
Over time, hardeners get darker.
Mechanical properties are not significantly affected.

Personally, I'd do a test or two.

[Dave Carnell]

Twenty years ago I bought some 2-part epoxy tile adhesive as military surplus from Morgan Marine. It was manufactured in 1950 says the MilSpec label. I recently mixed up a batch to fill a hole in some house trim. It cured normally and worked fine.

The only epoxy I have seen deteriorate with age was some 1:1 tabletop resin where the hardener gelled in about a year. It was a polyamide hardener vs. the more common polyamines.

[Bruce Hooke]

I've used Gougeon epoxy that old and it has given every sign of working, but it was much darker and redder than new stuff. However, I tried to reserve it for less critical uses like coating, rather than bonding. Is the strength of the epoxy really essential to the integrity of the centerboard trunk or will it be backed up with mechanical fasteners? If the former I might be inclined to use some newer stuff, just for piece of mind...

[John B]

I'm with Bruce. exactly .

[Stiletto]

I found a couple of small jars that had been left on the boat for a couple of years. I unscrewed the clear jar and had a sniff, yep epoxy, I assumed the other was the hardener as it had a golden colour.
I unscrewed the top and had a sniff, AARGH it just about lifted the top off my head with an incredibly strong ammonia smell.

This was a hell of a lot stronger than the smell it had when it went into the jar so some sort of change has happened.
I will save it and try it for some non boat application more out of interest than anything as it is only a small amount. The hardener did seem darker than usual.

[Rancocas]

What about freezing? I left some epoxy out in my barn with temperatures now in the 20's (F). Will it still be good when it warms up?

[JimConlin]

The resin might crystallize a bit in the cold. Warm it well in a water bath until the crystals dissolve.

[bainbridgeisland]

I investigated this question at work a few years ago. If the viscosity is workable requalify the stuff with a gel timer test: Mix 100 grams at 70 deg F and time how long it takes to gel. If within 20% of MFG specification, it is probably ok. We do a hardness test too but have never had one fail if the resin gels on time.

I talked to multiple MFG about this before we instituted it. They all agreed most epoxies are very robust, less so the hardeners.

In my opinion, despite the common one year shelf life, with proper storage epoxies have more like 10 year life.

[MuddyFeet]

Thanks for everyone's advice. I checked with Gougeon Brothers (not that I don't trust this forum!) and they confirmed that, when stored at room temperature there should be no problems. They did note, as mentioned here, that it would be darker. Again, thanks for the advice.