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How do I thin out 2-part epoxy? Answered

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:
https://www.instructables.com/id/How-to-make-homemade-micarta/
https://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.

Discussions

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TheFrankTurk
TheFrankTurk

7 weeks ago

There is a video out there where the guy thins his epoxy with a heat gun. That's fine if you want to accelerate the reaction that sets up the resin, not so great if you actually need to handle the resin longer. Normal off-the-shelf 2-part epoxy will thin with isopropyl alcohol, but you have to be VERY careful to add and mix in drops, not squirts. The other thing to consider is that thinned epoxy has WAY less structural value than unthinned. I have used thinned epoxy with (black) colorant to fill voids in guitar bodies. It takes a LONG time to set up but the thinned mixed spreads into skinny voids very well. You can get a nice glossy finish, but it's not good as a bonding agent or structural support anymore.

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StephanP13
StephanP13

3 years ago

I've used MEK to thin out a two part epoxy to spray a water treatment plant, and worked great. I think it was 4 part epoxy 1 part MEK or 5 part epoxy to one part MEK, I don't remember.

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david.r.usher
david.r.usher

5 years ago

2-5% acetone or lacquer thinner will make it thinner but it will not be as strong. Pot life is increased a little depending on the speed the volatile evaporates at. Note that this makes the epoxy flammable until cured. This also changes the color of the epoxy usually. Acetone has the most impact on viscosity with the least impact on strength. But is also evaporates faster than lacquer thinner. For more info and charts see

http://www.westsystem.com/ss/thinning-west-system-epoxy/

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Re-design
Re-design

7 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.

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yoyology
yoyology

Answer 7 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.

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mpilchfamily
mpilchfamily

7 years ago

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. 

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yoyology
yoyology

Answer 7 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.

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Prfesser
Prfesser

7 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!