What controls the cure time of epoxy? If I have 15 minute epoxy and I use hardener from a 30 minute epoxy set, what will the cure time be? Does the epoxy or the hardener control the cure? I have both epoxy and hardener leftover from different sets with different hardening times. Is there a problem using them together? Thanks for your response. Howard
Ultraviolet light (in some cases).
Temperature.
Completeness of mixing.
Purity of the mix (pure resin & hardener) vs. mixture of materials (thinning or thickening agents).
Age of the two parts?
I'm gonna guess 22.5 minutes. The two viscosities may not match well. How do they get different viscosities of resins and hardeners? I don't know.
Mix some up and see if you like the results. If you do, use up the stuff. If you don't, you at least learned something before throwing the stuff away.
I think the hardener is the greater factor, but the purity of the resin may make a difference, too.
It depends, too, on the joint you're using them on. Does the joint have some natural strength (interlocked in some way) or is the epoxy the sole means of making the joint? Is it a piece that you won't miss in flight or will the plane crash if you lose it?
The more I valued the part, the more I'd want a reliable epoxy to glue it in. At the other end of the spectrum, some folks like to use epoxy to coat a firewall or the area around gas tanks.
Marty
what many people don't understand about epoxy...
the "5 minute" epoxy means you have ABOUT 5 min from when you star mixing to when you can't apply it and get a good bond. It does NO mean its "cured" in 5 min. Full strength from 5 min epoxy takes 30 mi to 48 hrs.
30 min epoxy.. same basic story.. but full strength 2 hrs to 3 days.2 hr epoxy.. might still feel "tacky" 24 hrs later... can take a wee to get to full strength (keep it clamped 6 hrs minimum or you will b sorry
-- fhhuber50677
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Funny you ask.
Last weekend I grabbed some 30 minute epoxy and then grabbed the hardener bottle next to it (I saw the "3" out of the corner of my eye) and mixed them together with some microballoons.
Well, I had 30 minute epoxy and 3 hour hardener sitting next to each other.
It's a week later and it still hasn't set up...and I don't think it will.
Don
It could be that they are completely incompatible types. Many of the fast curing types are similar in composition. Nearly all of the longer cure types are very different animals. I used some stuff from JPL that would only cure in an oven at 200F for an hour or so. Otherwise, it would just sit there as a gooey mess. Once cured, it was stronger than aluminum!
Shoot the stuff you mixed up incorrectly with your heat gun and let it get pretty hot, then put a light bulb nearby to maintain some elevated temperature and maybe you can coax it into curing. If it won't set up. hitting it with the heat gun again should make it more liquid and easier to clean up with alcohol .
Charlie
Well, that would be good for an experiment but it was a small amount so I trashed it. I did set it in front of my tabletop heater for about 45 minutes...didn't help. I kept it around for a week just to see if it would set up but it was still unchanged when I trashed it.
Don
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