Heat and epoxy

[silentneko]

So we all know that cured epoxy can soften with heat, but what about when the heat is gone? Is the epoxy permanently damaged, or does it reharden?

[jacquesmm]

It becomes hard again.

[silentneko]

Awesome.

The reason I ask is I have become a big fan of heating my wood parts (cleats, brackets, hatch lip...) prior to neat coating/epoxy priming them. It makes a huge difference, instead of the resin pooling on the surface it gets pulled deeper into the wood. On occasion I'm adding a cleat or neat coating a part that is secured prior to glassing the rest and just wanted to make sure I'm not permanently damaging anything.

[OrangeQuest]

Interesting idea.

[jacquesmm]

I have to check that. Some heat in the sun is one thing (that was my reply) but deliberately heating the resin may have other effects.
Somebody should ask System Three.

[joe2700]

In the TDS for silvertip epoxy there is a "Heat Deflection Temperature" of 128°F and a "Maximum Service Temperature" of 160°F.
https://cdn.shopify.com/s/files/1/1000/ ... 2554198805

I read that as it gets soft above 128°F and could be permanently damaged above 160°F. I also remember the post cure temperature for silvertip being 140°F but I can't find the source for that. If you are using a different epoxy I would find the TDS from the manufacturer to find out what temps are safe.

[silentneko]

140 or 160 degrees is more then enough. I'm just heating it so it's warm to the touch. I've read that to be most effective you should heat a surface to about 30 degrees above ambient temp. If I had to guess I would say I'm maybe around 120 degrees or so.

[joe2700]

You should be safe then if you are using silvertip. Whenever I am doing the first layer of glass over bare wood I also raise temperature and let it drop as I work. End up with no bubbles as the wood is trying to pull the resin in as you say.

[OrangeQuest]

Yes, I would think the cooler liquid epoxy will cause the surface temps to drop as soon as it starts touching it unless you are heating the wood for a few hours in a oven where more than the surface is heated up.

Just me guessing out loud.

[OrangeQuest]

Now I have been epoxying outside in sunlight and the wood is being heated up and got bubbles due to the wood still being heated.