Epoxy Cures a Long Time - Doesn't it?

General Composites Discussions Composites Talk
#1

I’m pretty new to epoxy. I’ve been using PER for the last 8 years and am used to it being all done in a few hours – overnight at the least.

I mixed some System 3 with the fast hardener last night. I mixed some with some chopped up FG and that application took longer than I thought. So when I went to use the rest, it had already kicked off. It was smoking and hot. So I put it in a safe area and went inside. That was about 6:30 PM.

I came home from lunch today and it was still warm. The work was hard, but I could make an impression with my fingernail. How long does epoxy take to cure fully? My other epoxy work seems to take a couple days to get fully hard.

If my PER kicked off before I could use it, I would expect it to be cured in a couple hours.

#2

Most epoxy systems reach full hardness after 7 days @ room temp.

Theres a lot of things that will cause a layup to smoke:

-Resin rich (puddling)
-Working in the sun
-“Pot Life” effect in the actually layup (due to being resin rich).
-To many layers applied at once.

The only way to know when epoxy will cure is by reading the manufacturer’s literature. Then factor in the temperature your working in. There really is no rule of thumb.

#3

i wouldn’t demold an epoxy part in less than two days… polyester kicks fast and hard, epoxy is more linear. and after you demold the part, don’t put it somewhere where it can bend, cause it might.

#4

I guess I should clarify ---- the smoking epoxy was in the cup – not on the piece :wink:

#5

Thanks for the info. I never realized epoxy takes so long. If y’all wouldn’t have told me that, I might’ve messed up some parts with my impatience. :slight_smile: