Epoxy hardener expiration ?

I hope the guys with more experience can help out with a bit of advice regarding hardener properties, or any chemist around ?

I got the hardener in a plastic container and realized that the cap cracked from overtightning. I probably realized this too late, fixed the cap but the hardener turned somewhat redish, darker colour.

Question - what does this to the chemical properties ? It probably reacted with air - but in a half full airtight container there is still air right, but does not necessarily turn darker.

The hardener seems to work the same way (subjective opinion- don't know if the mechanical properties actually changed).

Supplier has no idea about this.

Opinions ? Is it safe to use it ?

Regards,

Florin,
That's a hard one because there are so many kinds of epoxy curing agents on the market. Epoxy resin is all pretty much the same and does not react with air readily. The only additive is usually a reactive dilutent to make it easire to wet out fabric. I have used some high temp hardner that had a distinctive reddish tint to start with. Does it have any chemical names on the container? perhaps TETA, Polyamide, or something like that?
Kevin

Kevin,
The resin system comes from Bostik/Resoltech, called Epiphene RE4020, hardener DE 4020. I think I remember the hardener is based on modified aliphatic amines. Should have mentioned this earlier. The hardener is a bit yellowish from the start, but that container turned darker, a bit redish.

Regards,

you have a bit of moisture in it. even though it is not west system stuff, give them a call.

I'm looking at an industrial formulator's catalog (magnolia plastics, www.magnaepoxy.com). Their Modified Aliphatic Amine is a general room temp fast cure hardner. Their comments: "accelerated reactivity", "fast cure in thin sections", "fast cure low viscosity". They offer the folllowing general note:"Unsealed containers of each component will allow the component to absorb moister form the air - especially the hardner. Extensive water absorption by the components will alter the chemistry of the reaction and change the properties of the cured materials". Hope this helps!

Thanks guys,

I guess the contaminated hardener should be ok for making non structural fillings.

Regards,

test a small sample first