Article: 1901
By Robert Krausert, January 2010

Ever interested in techniques for curing epoxy? Here is a discussion that was captured from the RocketNW list server, and might help you when trying find methods to cure epoxy.

Scott Barfield Asked:
Any of you guys ever built a tube curing oven? I am looking for info on temp control circuits.

Sam Grado Responded:
Look for used laboratory equipment, specifically clinical lab equipment. I have used a lab incubator as a curing oven for 5 years. They offer excellent temp control & monitoring and are about the size of a large mini-fridge. They usually come with a clear door (poly or tempered glass). I bought mine for $125.00.

Greg Clark Responded:
I used a temperature switch that I got at the local appliance repair shop.  I think they’re used to turn on and off the heat in things like clothes dryers.

Like this: http://www.thermodisc.com/productdetail.asp?ProductID=17

Or you could build this!!!

http://www.sparkfun.com/commerce/product_info.php?products_id=81

Marty Weiser Responded:
I just adjust the heat source and any venting to get the temperature I want in mine.  1″ foil faced foam panels that are held together enough to not fall apart and a 300W light bulb gives about 150F in a 2′ x 2’x 4′ oven. Taping the seams and weighting the lid would increase that a fair bit as would using 2″ thick foam.  But it would be harder to break down and store.

Bob Yanecek Responded:
I used 1″ foil covered foam to make an oven 2′ X 2′ X 6′ then added a ‘milk house’ style heater that has a built in (but uncalibrated) thermostat. While temperature comes up fast, it takes me about 10-15 minutes of fiddling to adjust the thermostat to achieve any particular stable temperature (max is about 180 deg F).

Greg Deputy Responded:
My favorite setup was the guy’s who took a standard electric oven, then added a fan and a foam box on the front.  Automatic thermostat, as well as timer.  If you have the space and a 220v outlet, you can find old electric ovens for free or close.

Andrew MacMillen Responded:
I did pretty much the same, but over the top, and longer for hybrids 😉 I thought I’d shared this back when, but don’t see it.

http://www.macmillen.com/rocketry/cure_oven/

Greg Deputy Asked:
Is 170 hot enough?  The epoxy I have wants a post cure to 250, but maybe I just have something weird…

Andrew MacMillen Responded:
I use System Three T88 general purpose epoxy. I cure it at at 90F, which will cure in 3 hours but I usually stop at 2. Once my air frame section section is done, I post-cure at 120 for 1 hour to finish all the cross-linking, and maybe some inter-layer bonding. T88 has a max service temp of 160F, so I stay well below that to prevent de-linking.

System Three & West Systems are both marine oriented, so are lower temp than Aeropoxy. It’s ‘glass’ temp is around 200F, so even it shouldn’t go over 150F where it looses 90% of it’s strength. I think some of that may be recovered when cooled.

High temp special epoxies like the one ShadowAero used to carry, prepreg cloth, etc are a whole different story.

Andrew MacMillen Added:
One other note: elevated temps don’t allow as much penetration. That’s not so critical if you’re laminating over peeled cardboard or making standalone composite tubes. But it is a factor for bond strength at centering rings, fin roots, couplers, etc. where 75-80F for the initial cure might be better.