High Performance Room Temp. Cure Epoxy?

Discussion in 'Composites' started by undean, Oct 19, 2019.

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  1. Oct 19, 2019 #1

    undean

    undean

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    I am not as well acquainted with epoxies as I once was and am looking for a high performance room temperature cure epoxy. Preference to those with Tg above 135*F, tensile yield above 10ksi, compression yield above 14ksi, and a tensile elongation below 5%. If someone knows of such an epoxy please post it here.
     
  2. Oct 19, 2019 #2

    SoaringEagleRick

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    Is this something you could work with? Hexion Epikote LR285, 3 different hardeners (285,286 & 287) can be used for different processing times. The latter two can be a little harder to come by.
    https://www.ezentrumbilder.de/rg/pdf/td_en_LR285_eng_180310.pdf

    The Tg for unheat treated is about 135 F as you specified, but the operating temperature is a bit lower for the un heat treated epoxy. See page 1.1 - 15 for the Tg curves
    Page 1.1-16 specifies the tested properties. These are however for a sample that is room cured and heat treated afterwards (with the 287 hardener). The strengths are roughly the values you specified
     
  3. Oct 20, 2019 #3

    Aerowerx

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  4. Oct 20, 2019 #4

    pictsidhe

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    Adhesive, laminating, infusion?
     
  5. Oct 20, 2019 #5

    undean

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    SoaringEagleRick, Thank you, that might be feasible and the thorough datasheet is reassuring.

    Aerowerx, Thank you but unfortunately it appears they do not have an epoxy that comes close enough to my criteria.

    pictsidhe, Laminating or infusion.

    I have sent Fibreglast and R&D Resin an email asking for more information as it appears they may have system(s) which meet my criteria but they do not have the best datasheets. Still looking for others if folks know of them.
     
  6. Oct 20, 2019 #6

    SoaringEagleRick

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    No problem, by the way; this is a nice summary of the general aviation epoxies of Hexion: https://www.hexion.com/en-US/applications/composites/aerospace/general-aviation/
    Of course there are many other suppliers of epoxies.

    One drawback that I do want to mention is that the L285 epoxy can burn and is not self extinguishing, so keep that in mind for your application.
    Looking at the datasheet of Hexion LR940, it has slightly lower mechanical performance but it is self extinguishing. So that might be a better alternative in some places.
    https://www.swiss-composite.ch/pdf/t-MGS-LR940-e.pdf
     
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  7. Oct 20, 2019 #7

    wsimpso1

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    Tensile strength above 10,000 psi and modulus above 150,000 psi? Tall order ...

    I am curious as to what fiber you are laminating to need these characteristics. Most fibers have strain at failure of 2% or less, so laminates are fine with almost any resin failure above that. Need high crush strength for fasteners?

    Billski
     
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  8. Oct 20, 2019 #8

    opcod

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    MGs or new name since 4yrs HExion is a certified and had better caracteristic in every aspect vs the west system. West is quite fine, but it's intended for boat. The people using that for airplane are quite the same who try to safe penny at wrong place or having a cessena and putting cheap bolt. Because they are too cheap to get the proper certified one. Building an aircraft and touching the structure is the key component. If the price diff of 10$ is too high from the West vs Mgs.. then there's whay more problem here. As you have to understand what the spec is and know what is the poisson ratio and other factors. Especially if you build your own design, in that case the designer should be all well aware of all this as he need those in order to do the full calculation. So if i need to do a wheel pant fairing and someone give me a vinlyester, an el-115 or a west can.. i might used it to build them, but if not, go with proper resin system. Even the high class catamaran don't used west to build...
     
  9. Oct 20, 2019 #9

    User27

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    If you go with L285, the properties increase markedly if it is post cured even to 50 or 60C (122 to 140F), for structural work I would only use H286 or 287, H285 is rather too fast.
    Perhaps even leave your part in the sun in a dark coloured box (but check the temperature).
     
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  10. Oct 21, 2019 #10

    undean

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    I appreciate the inputs thus far and hope other candidates pop up.

    Billski, I'm unsure if the 10ksi or the modulus above 150ksi is what you are referring to as a tall order but even those mentioned that do not meet the 10ksi tensile strength have well exceeded 150ksi tensile modulus. I plan to use a fiber that is T-700 or better.
     
  11. Oct 21, 2019 #11

    mcrae0104

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    In an OSH forum posted by Birdus, Scott VanderVeen mentions a product from the makers of Aero-poxy suitable for 300 deg service temperature. Looking at the PTM&W website, it is not clear to me which product this might be. Might be worth contacting Scott to ask.
     
  12. Oct 21, 2019 #12

    BoKu

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    2080 is what we used in a set of jet tips that will be painted black. We tested it and found the max Tg around 260 F. We built a simple hot box to post cure to about 170 F.
     
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  13. Oct 21, 2019 #13

    proppastie

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    Is Tg of 135 F high enough for on the ramp in AZ (USA) .....just how hot do the white painted gliders get?
     
  14. Oct 21, 2019 #14

    ScottV

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  15. Oct 21, 2019 #15

    opcod

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    A guy in Nevada started an EZ build and plan to be clearcoat all in black, or direct fiber visibility. If i remember it might used Ptm also. But, while it's high temp resin... If i get a flight in the first 2 month of the 'servicability' of the bird.. ok. But after that, i'll pass. Sitting in a structure piping hot from the sun, just for the look of it, i'll pass.
     
  16. Oct 21, 2019 #16

    Voidhawk9

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    The big issue with EZs and heat isn't so much the epoxy, it's the foam. The insides of the wings will melt first.
     
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  17. Oct 21, 2019 #17

    Marc Zeitlin

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    It's both. The Tg of the RT epoxies used is generally about the same as the maximum temperature of the foams used, so it'll be a race to see what fails first.
     
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  18. Oct 23, 2019 #18

    pictsidhe

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    That sounds unwise.
    There are specialist IR reflective black paints that are nearly as cool as regular white.

    I've found that Sherwin Williams has a line of cooler paint pigments for plastic siding. They don't do black, but can mix almost my full set of WWII RAF colours (except the black!), some of which are pretty dark. Ask for 'Vinylsafe'.
     
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  19. Oct 23, 2019 #19

    BoKu

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    BTW, the reason we chose the 2080 was because it had the best compromise of properties and low viscosity. It's not quite as thin as our standard lamination system, but close enough, and the price is comparable. The reason we don't use a lot of it is that parts made of it are is very tender and prone to cracking until treated to 100F, and it is also more prone to exotherming where there are solid volumes of it like right under the vacuum tap. It also feels like a more sensitizing system; the hardener is pretty much straight TETA like in the old "Redeye" 815c/3234 mix. Brrrrr...
     
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  20. Oct 23, 2019 #20

    proppastie

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    Are there systems that heat cure as they exotherm?
     

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