Heat curing epoxy

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jeff k
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Joined: Tue Feb 03, 2015 4:51 pm

Heat curing epoxy

Postby jeff k » Fri Dec 04, 2015 5:43 pm

Hi All,
I'm building a squirt, restoring 2 GW Invaders and a 1975 Glastron GT 150. Yea.... I should have my head examined. Anyway, The squirt and 1 invader are in my basement for the winter and I'm doing a dual build and restoration. The temps are around 60 to 64 in the basement over the winter months and epoxy takes a LONG time to dry on my fiberglass cloth layups. I have been heat curing the epoxy with halogen work lights and have found I can accelerate my drying times from 48 hours to about 2 hours by applying the heat lamps. My question is, by doing this am I degrading the epoxy in any way? I have been using MAS low tox, slow drying hardener and it is fine in the summer months as far as dry time. In my cold basement it is SLOOOOOOW to cure and that's why I started using the heat. Good idea?, or bad?
This boat project is destroying my wallet, But it is enriching my soul.

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Re: Heat curing epoxy

Postby slug » Sat Dec 05, 2015 4:58 am

Jeff; I'm a fan of the Low Tox (allergies) and I've used it in my last two builds. I have a heated (gas) garage, and when I do my epoxy (last thing before I shut down for the day) I turn the heat up to 90 deg. F.

Works for me with no adverse affects.


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Re: Heat curing epoxy

Postby Ibrew2be » Sat Dec 05, 2015 8:12 pm

I've been puzzling over this question of yours for a couple of days now. I think what you are doing is fine, and won't compromise the physical properties of the epoxy. I don't think the approach you are using gets the epoxy hot enough to do any harm. Here's my rationale.

There's an old chemist's rule of thumb which says that the rate of a chemical reaction about doubles for every 10 Celsius degrees that the temperature is raised. If we say that your reaction time went to 2 hours from 48, in round numbers, that would imply a temperature rise of about 55 Celsius degrees. That's about 100 Fahrenheit degrees. So by these calculations, your epoxy would be at about 160F.

Question: is that too hot? The reason that I think it isn't is because in some applications, temperatures in the range of 150 to 200 Celsius are used to cure the resins. Your temperature is likely well below that.

If you had one of those infra red temperature sensors you could check out my back-of-the-envelop temperature calculations to see what temperature your hull is while the epoxy is curing.
Barry Shantz

Imp built and launched. Thinking hard about Boat 2.0

jeff k
Posts: 36
Joined: Tue Feb 03, 2015 4:51 pm

Re: Heat curing epoxy

Postby jeff k » Sun Dec 06, 2015 6:13 am

The 150 to 160 degree figure would be fairly accurate. I only do this on small localized areas and repairs. A few times the area got hot enough to see some steam/smoke come off the epoxy. I backed the lights off at that point. It was a learning curve at first. The epoxy seems to harden nicely with good strength.
This boat project is destroying my wallet, But it is enriching my soul.

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