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Epoxy Mixing Ratios.....

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Epoxy Mixing Ratios.....

Old 04-03-2010, 06:47 PM
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Juan Rodriguez
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Default Epoxy Mixing Ratios.....

Ok guys (and gals )

I know this topic has been "partially" discussed before but I could not find a specific answer while doing a search..... So here is the "specific" question for the experts and folks with experience......Here is the scenario.....

While discussing "working time" of using epoxy today with one of the fellas , I was informed that I could vary the working time of a two part epoxy by simply using 1/2 of the recommended hardener.... In other words, if I wanted to lengthen the working time of say, 30 min 2 part epoxy, I could mix it at a ratio of 1:1/2(of hardener) vs the "standard" 1:1 ratio.

I would like to hear from the forum members "why" this practice would be OK or "why" this practice is not a good idea.....

I'm conducting an experiment as we speak using this un-conventional mixing ratio to see if it fully cures using 30 min Devcon 2 part epoxy...

Thanx in advance for all of your comments !
Old 04-03-2010, 07:33 PM
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Gray Beard
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Default RE: Epoxy Mixing Ratios.....

I have read that you can do this and lengthen the cure time but have never tried it. I have tried to add more hardener to quicken the cure time but it didn't work or I was too timid when I tried it?
Old 04-03-2010, 07:52 PM
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Default RE: Epoxy Mixing Ratios.....


ORIGINAL: Gray Beard

I have read that you can do this and lengthen the cure time but have never tried it. I have tried to add more hardener to quicken the cure time but it didn't work or I was too timid when I tried it?
Thanx for your comments, Gray.......

Please keep them coming, fellas.....[sm=teeth_smile.gif]
Old 04-03-2010, 09:03 PM
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pmw
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Default RE: Epoxy Mixing Ratios.....

RCReport magazine did an excellent study of this question a couple of years ago. They found that the working time can be varied as you suggest, but the strength was hardly affected. I don't recall the various ratios they tried, but I don't think went as far as 2 to 1. Seems like about 40% was as far as they went. About 100% epoxy and 60% hardner. I'm interested in your results.
Old 04-03-2010, 09:28 PM
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Charlie P.
 
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Default RE: Epoxy Mixing Ratios.....

I would not recommend it. I have done gallons of epoxy with various boating projects and nowhere did I find messing with the mix ratio as a means of adding time. Temperature, yes. Various hardeners, yes. But starving the hardner will result in uncatalyzed resin that never hardens. The 50/50 mixtures have more than just the resin & hardener in the seperated bottles. You may get away with it or you may not. Why risk it. Just get a longer pot life epoxy (I only use 30 minute or even longer with the West & System Three epoxies).

Here's a free read. http://www.systemthree.com/sys3news/?cat=6 All about epoxies and additives.
Old 04-04-2010, 08:33 AM
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Juan Rodriguez
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Default RE: Epoxy Mixing Ratios.....

Thanx for your responses so far, fellas....

The result of my "experiment" so far is that while the "mix" is not a "gooey mess", the small amount I mixed has not fully cured. You can press your finger into the epoxy and leave a fingerprint and you can stick a tookpick into the epoxy to see it has not fully cured. That small batch was mixed about 16 hours ago. We'll see what happens with a little more time....

Thanx for the link, Charlie. Looks like a good read !

Any more comments would be welcomed.......
Old 04-04-2010, 05:22 PM
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pdm52956
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Default RE: Epoxy Mixing Ratios.....

OK, I don't glue for a living but I do paint. Some of the products are epoxy based. There are reasons for the mix ratio that's called out with any resin based material. You can in fact vary the cure times, but as said previously, you will also vary the strength of the hardened material if it hardens at all. There is a chemicaql cross linking that occurs when you mix the base with the catalyst that has to take place as it was formulated in order to achieve maximum performance. A little off? No big deal but cutting the ratio to a 2:1 mix wouldn't be recommended if it's intended to be a 1:1 mix.

Just my .01

Oh, don't mix in waxed cups either!

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