epoxy cure time

[darryl]

Just wondering- today I coated the inside of a steel can with epoxy as a barrier against moisture. Normally a full 24 hours is suggested before putting it to use. I've had it in the oven at 150F for about five hours today, and it's been out for a couple hours. It's completely tack free and has no smell left whatsoever.

Anybody have a rough guestimate about relating temperature to cure time? How far along am I now by comparison to room temperature cure? Have I got the equivalent of a day or so into it?

It is a container for a one-shot wood glue applicator. I have the pump almost complete, and I'm basically at the point of using 5 min epoxy to glue the cover on the can. The can is the bottom half of a 1 lb propane tank. I'm going to work on it some more, then take a few pics if my camera has power.

I can look stuff up like anyone else, but I thought maybe somebody would know this off the top. Maybe also there's a proper or maximum temperature to use for fast curing without damaging the coating or compromising the bond.

[Dr. Rob]

Yes.

A fella at Scotch 3M Aerospace once told me that you can count on half the cure time for each ten degrees centrigrade above ambient (=room temp) temperature.

ie a one-hour cure time @ 20° becomes a half hour @ 30°.

Within limits of course; otherwise outgassing and other problems may arise.

Rob

.

[darryl]

Thanks, Rob. That means that at 65C, which is what my setting was, the 24 hours worth of cure took less than two hours. So my five hours of heat has at least given it a couple days worth at room temp. No wonder it was tack-free to touch. I'm good to go tomorrow-

[ptjw7uk]

Remember the higher the cure temperature the runnier the epoxy gets!
(Dont ask how I know!)

Peter

[darryl]

Yeah, I used that to advantage when rolling the can around to spread the epoxy. I started with it cold, but then put it in the oven for several minutes. It certainly never got like water, but it thinned out pretty good anyway.

I'm having some trouble with the piston- air is leaking past it and affecting the uptake of the glue. I anticipated this, but thought I might be able to get away with no ring on the piston. It seemed to hold air while I was testing it, but obviously it's not good enough. Now I'll have to add the o-ring, which I probably should have done from the start. Easy enough, just won't be able to use this tomorrow- oops, it's today already, and well into it. Must go to bed now.

[Benta]

My favourite 24-hr epoxy for glueing is UHU Endfest 300. Don't know if you get it over on your side, probably has another name.
When i use it, I either use a big heat pistol for larger pieces, or I put it in the oven at 150 degreees Celcius (it's rated for 180 degrees max).
Curing time in the oven? 5...10 minutes, and the strength according to the datasheet is 3 times higher than if I had let it cure at room temperature for 24 hours.
It does get nice and runny at high temperatures, which I see as an advantage, provided your fixture is good.

Cheers,

Benta

[darryl]

I ran my oven at the lowest temperature it will come on at, since I didn't want to have any issues with air quality in the house. Just me here anyway, but I do have to live in the house and I've sickened myself before with fumes, etc. Years ago, but still- There was a slight smell while mixing the epoxy, but that went within the first 15 minutes I'd guess, and the heating didn't raise any smell at all. In fact, I could not smell it at all after the cure started, nor in the house at all at any time during the 5 hour bake. I'm happy about that, and the cure time is short enough that I can mix and pour one afternoon, then use the result the next day. That's as fast as I need it to work, so I've pretty much got my parameters down, for this epoxy at least.

The glue pump project might get relegated to another use, probably as a cutting fluid pump. It seems to work well with water, but not so good with glue. I'll likely go back to the last idea for glue, which is a pressurized container with a trigger operated exit orifice and flow control adjustment. I have previously worked out most of the details for that, so-- well there's a couple of projects defined a little better now.

Got the dovetail drawer assembly press operating a few days ago, and the bugs worked out. Now to remember to get some AA's charged and take the camera to work and take some pics-