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Thread: Mixing Epoxies?!

  1. #1
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    Default Mixing Epoxies?!

    I need to fix something with epoxy and fiberglass about every 5 years. Last year I patched a hole in my wife's rowing shell, so it may be a while before I do it again. With that in mind I sold my laminating epoxy to someone who offered an irresistible price. Well, actually I thought I had some small bottles, but it turns out they are SystemThree T-88 glue, which is much too thick to laminate with.

    I also have some ESP155 waterproofing epoxy, which is much too thin to laminate with. BUT, could I mix them together?

    Yeah, I know it sounds foolish, but when I need it, I will only need a couple ounces and hate to spend $60 on something I will not use again for years.

  2. #2
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    Default Re: Mixing Epoxies?!


  3. #3
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    Default Re: Mixing Epoxies?!

    Quote Originally Posted by Ian McColgin View Post
    Good referral Ian.

    I was faced with the same predicament recently Toller .
    So, I did a little test.
    I mixed up a small batch of each, then poured 1/3 of each into a third container and mixed well.
    Then tensile tested them to failure a week later.
    Less than 10% variation between them all!

    So, yes you can mix brands but mix each brand separately first, then mix them together.
    They were West System 207/105 and System Three.
    The former was 5 years old, the later 8 years old.
    Last edited by Tom Christie; 09-01-2018 at 11:58 AM. Reason: Epoxy Name Correction

  4. #4
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    Default Re: Mixing Epoxies?!

    All you did was test those two epoxies and show you could mix without a fire or significant strength loss.

    That does not prove any other epoxies could be mixed. IMHO its not justified to imply any epoxies would work.

    How did you do the tensile test?

  5. #5
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    Default Re: Mixing Epoxies?!

    Your powers of observation and deduction are impressive upchurch, you'll go far.

    I used broken (failed) tensile test pieces from the university lab.
    Just glued them back together and screwed them back into the reverse press.

    Did you read the referred-to thread?
    The general consensus is, they can be mixed.

  6. #6
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    Default Re: Mixing Epoxies?!

    I would not do it to save a nickel.
    Even if the mix went off, one would not be familiar with what is about to happen.
    Toller is talking about blending them TOGETHER in one batch.

  7. #7
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    Default Re: Mixing Epoxies?!

    No I didn't read it.

    Well now I have and I didn't see anything about mixing 2 different epoxies as you proposed.

    Thanks for the explanation of the tensile test. Sounded reasonable and its really great to have the right equipment, isn't it? Did it break in the bonded joint? I'd worry about the broken specimens having damage outside the secondary bond joint.
    Who else will have access to such equipment?
    Last edited by upchurchmr; 09-01-2018 at 12:51 PM.

  8. #8
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    Default Re: Mixing Epoxies?!

    "No I didn't read it.

    Well now I have and I didn't see anything about mixing 2 different epoxies as you proposed."

    That's right, I mixed them differently, imagine.
    I was offering my experience to the OP as I thought it may be helpful.


    Thanks for the explanation of the tensile test. Sounded reasonable and its really great to have the right equipment, isn't it? Did it break in the bonded joint? I'd worry about the broken specimens having damage outside the secondary bond joint.
    Who else will have access to such equipment?

    Of course they failed at the epoxy joint or I wouldn't have been able to make such a report.
    The metal test pieces were, I believe, a blended titanium alloy with very high tensile strength.


    I'm sorry if you don't like my posts, I was just trying to help the OP with what I had experienced.
    Please don't read more or less into my posts.
    And I should note, others may experience different results.
    Play safe.

    Now, I have to go and buy another joist hanger because I don't seem to be able to count very well...

  9. #9
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    Default Re: Mixing Epoxies?!

    Tom,

    Thanks for you explanation.
    Lots of "experience" gets reported here with no details or backup.

    Lots of it directly contradicts what I have seen.

    Generally I look for something that actually resembles facts, just to try to understand.

    I'm puzzled that you are so offended with a few question.

    Marc

  10. #10
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    Default Re: Mixing Epoxies?!

    Mixing epoxies like this is the height of hubris, arrogance and stupidity (mostly a male thing, I think)!
    So go ahead. It's only human, and it is only your loved-ones life at stake.
    My two centavos, anyway. I pretty sure any epoxy manufacturer would advise against it.

  11. #11
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    Default Re: Mixing Epoxies?!

    Ive mixed the hardener of one brand with the base of another epoxy coating ,after a small test...for a HOUSE PORCH.
    At swap meets , sometimes one will find a gallon of stuff without it's partner for 5 bux.Fishermans in Seattle fer instance.
    Not for a freakin boat.

  12. #12
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    Default Re: Mixing Epoxies?!

    I had guys working for me mix base with another epoxies hardener.

    There was a quick/ violent fire. Guess who got in trouble.

    Of course that was not quite what Tom Cristie suggested.

  13. #13
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    Default Re: Mixing Epoxies?!

    Looking at it another way, you could probably just laminate with the t88, it'll be a thick glue line, and probably less than ideal strength, but, it's a know quantity. Of course, intended finish and possible weight restrictions could make this a bad solution.

  14. #14
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    Default Re: Mixing Epoxies?!

    In this case, the answer is no.

    ESP 155 waterproofing epoxy http://www.epoxyproducts.com/dataesp155.pdf is somewhat of a CPES. It contains 24% VOC, which is a lot of solvent. It also says 74% solids in the properties table. CPES is more like 75% solvent, 25% solids, but that isn't important here. Solvents are not good for thick layers or fast curing epoxy. The solvent has to evaporate off before the epoxy cures or the trapped solvent causes problems. So ESP 155 is strictly a coating. The strength is also low compared to laminating resins. 3500 psi isn't shabby, but with 10% elongation, I would expect it to be fairly soft.

    I am not "The Chemist" but I have been a chemist. Lab rat anyway. Ordinarily, almost all of the room temperature cure laminating resins we typically use should be reasonably compatible if only you had enough information to get the mix ratio correct. Don't start mixing CPES or 5 minute epoxy with laminating resins though. Most of the ordinary laminating stuff is an amine cure. 5 minute epoxy hardener is normally a sulfur compound that explains why it stinks. I would be surprised if Marc's firepost #12 wasn't caused by mixing too much 5 minute hardener in a large batch. 5 minute reacts fast and dumps a lot of heat, so large batches don't have enough surface area to cool. I don't know how laminating resin reacts with 5 minute hardener, but badly would be no surprise.

    The epoxy and hardener have to have the right number of linkable parts in each. The numbers we need are epoxide equivalent weight and amine number. To cure properly the numbers of 'links' in both components have to match up. You use those numbers to calculate weight of each part to needed get the same the number of links on both of them. Since you normally can't find those numbers, you can't calculate how much West hardener to use with MAS Resin. You can mix the correct amount of west with west and mas with mas and then mix them both together. The result will be some kind of hybrid. You won't know how well it works until you try, and you won't know how well the mix weathers for quite a while.

    It is like two sets of short wiring harnesses with several plugs on one and several sockets on the other. If you have a pile of short harnesses with two plugs each and another with three sockets each, you need three with plugs to mate completely with two with sockets; six plugs, six sockets. Just like a 2:1 epoxy. If you know how much each type weighs, you can weigh out piles of each and make a network with all of the plugs and sockets mated up. The plug on the epoxy is an oxygen atom stuck to two adjacent carbon atoms. The little triangles are under a lot of stress because the bonds want to be at a much different angle, so it really wants to react with something. The socket on the hardener is an amine, which reacts easily with epoxy.

    I used broken (failed) tensile test pieces from the university lab.
    I liked your input, so take my comment with a grain of salt. University lab for sure. An industrial lab rat can't use the 'F' word because a snake, I mean lawyer, will bite him. Titanium isn't the easiest thing to bond.
    Last edited by MN Dave; 09-01-2018 at 09:29 PM.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

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