Hi, 

I have successfully used resins that were stored for 10-15 years. It's the hardeners that go bad by water and carbon dioxide uptake, depends a lot on the packaging. The old hardener I used was stored in sheet metal bottles inside a can (air and water-tight), so it was discoloured (turned red) but still worked fine otherwise. Plastic containers unfortunately aren't that tight, if the hardener turns cloudy or even solidifies then it definitely needs to be discarded.

Resins can definitely be used much longer than the usually recommended 1 or 2 years or so shelf life, the manufacturers tell you that so they can sell more stuff, but I've seen hardeners go bad earlier than that depending on storage conditions.
If you invest a lot of money and time in a part, then buy new resin, or at least new hardener if you're not sure and use the old stuff for mold making, test runs etc.

The polyamine hardeners are usually light sensitive.  They can be stored longer in the dark.  They will darken and still be good but as brainfart says if they have gone solid then they are well past it.

Hi Donnacha,

Our IN2 Epoxy Infusion Resin has a stated shelf-life of 12 months. A bit like with food, this stated shelf-life is more of a guide rather than a hard and fast rule. Inside of the 12 months, we guarantee that the properties of the resin (in terms of its cured mechanicals, pot-life, cure time etc.) will be within tollerance of the published specification. Outside of the 12 month period the resin will often still work and still cure however the cured properties and particularly the pot-life and cure time will start to go outside of tollerance.

As stated by the other posters, it's certainly true that the resin itself is far more stable (ours have a 3 year stated shelf-life) but the hardeners are much more sensitive and really do start to go out of specification when they're older. I've certainly used our EL2 and IN2 well out of date and they have cured but as the others have said, if it's a critical part I would at the very least recommend that you replace the AT30 Hardener.


Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Thanks for the replies and advice, I'll definitely take it on board, Donnacha.