Instructables

How do I thin out 2-part epoxy?

I'm wanting to make some micarta-like material, using two-part epoxy and paper. I've done a test run, and the material was rigid after it had cured for a few days, but didn't cut like I hoped it would, because the epoxy didn't penetrate the paper. Part of the issue was that the paper was coated, but I'd also like to thin out the epoxy some so that it will soak into the paper better. I'm inspired in this endeavor by these two instructables:
http://www.instructables.com/id/How-to-make-homemade-micarta/
http://www.instructables.com/id/Mokume-Kireji-DIY-Woodgrain-Composites/

The epoxy I'm using is 3M Scotch-Weld DP-190. The label says it contains epoxy resin, polymeric diamine, kaolin, and carbon black. The complete MSDS is here. This is what I'm using, because it's what I have. Got a case of these two-tube dispensers cheap at a yard sale. :-)

So, what can I use to make this more liquid? Right now the consistency is a little bit thicker than honey. It doesn't spread out when applied to paper, and doesn't soak in at all. My limited knowledge suggests that toluene, listed on the MSDS, might work, but I'm hoping for something a bit less volatile.

I'm aware that whatever I do is likely to extend the curing time, but that's not necessarily a bad thing.

Re-design2 years ago
Try thinning it with alcohol. I used alcohol to thin epoxy back when I flew R/C planes. You will extend the curing time and my lose a bit of strength but not much.
yoyology (author)  Re-design2 years ago
Thanks. That's one of the things I was finding as I searched online. I also had a recommendation to use warm water to raise the temperature of the two parts before mixing.

I may try a couple of small batches, one with alcohol, one warmed, and see how they do.
You don't use a 2 part epoxy. Its not the same thing as a fiberglass resin. You need to use a fiberglass resin because it is more fluid and will permeate materials like fiberglass and paper.  

As you have found 2 part epoxy is too thick and won't work. I'm afraid there is no way of thinning the mixture out so it will be absorbed by the paper. If you do find a chemical that will safely thin it out it will likely never cure at all. So get a can of fiberglass resin. You can pick it up at most auto parts stores for about $15. 
yoyology (author)  mpilchfamily2 years ago
I know that fiberglass resin would work best for this application, but I was hoping to find a way of using what I've got.
Prfesser2 years ago
Epoxies can be thinned with alcohol, but don't use the common 70% isopropyl alcohol (rubbing alcohol).  Either 91% isopropyl, or denatured alcohol (Lowes, Home Depot, paint stores) should work.  Yes, it will make the product weaker, though I don't know how much weaker.  Not enough to be a serious problem for your application.

The purpose of kaolin in DP-190 is to thicken the mixture.  I know you got your epoxy quite inexpensively, but ideally you would want an un-thickened epoxy.  A quick look on Ebay shows a 9 oz kit for $20 with free shipping.  Laminating epoxy is much thinner and soaks into most paper pretty easily.  I've made parts for model rockets with several layers of kraft paper soaked in laminating epoxy.  Works a treat.  And you can buy different curatives for the epoxy resin:  fast, slow, and medium.

Polyester resin is indeed thinner than your epoxy but it reeks; can't use it indoors.  Laminating epoxy is about as thin, or thinner, than polyester resin.

Good luck!