Thinning Epoxy?

Discussion in 'Materials' started by Frog4, Oct 17, 2011.

  1. Frog4
    Joined: Oct 2011
    Posts: 150
    Likes: 2, Points: 0, Legacy Rep: 12
    Location: Arizona desert

    Frog4 Proletariat

    What to thin epoxy with?

    Does anyone know where I can find research with cross-sections cut that show there's proof of the epoxy penetrating plywood?

    Some of the literature I've read states that most "thinners" evaporate rapidly, which would defeat the purpose of them actually being able to "penetrate" plywood ...
     
  2. gonzo
    Joined: Aug 2002
    Posts: 14,132
    Likes: 538, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Never thin epoxy. If you need less viscosity either heat it or buy a low viscosity formulation. Thinners degrade epoxy
     
  3. Jimbo1490
    Joined: Jun 2005
    Posts: 785
    Likes: 41, Points: 28, Legacy Rep: 527
    Location: Orlando, FL

    Jimbo1490 Senior Member

    Use Heloxy 61 or 68. Increase the curing agent fraction to regain stoichiometry.
     
  4. Jimbo1490
    Joined: Jun 2005
    Posts: 785
    Likes: 41, Points: 28, Legacy Rep: 527
    Location: Orlando, FL

    Jimbo1490 Senior Member


    Evaporation does not defeat the purpose at all! In fact it's desirable. Epoxy primer is just epoxy resin with some pigments added and diluted with a 'non reactive' diluent. A non-reactive diluent is incapable of meshing chemically with the resin system during cure, so if any remains in the mix after the cure is well under way, the cured state properties will be severely degraded; you'll get mush.

    But the diluent need only remain in the mix long enough to get the resin to where you want it, like shot out of a spray gun or saturated into cloth or in your case, brushed onto wood. If you choose a very volatile solvent like MEK for the diluent, then its a virtual certainty that the diluent will have all evaporated by the time the resin cures. So in the end all that will remain is undiluted resin, which is a good thing.

    Reactive diluents like butyl glycidyl ether (Heloxy 61) or neopentyl glycol glicidyl ether (Heloxy 68) ARE capable of meshing chemcally to become part of the cured resin mass so the need not evaporate before cure (and they won't).

    There's nothing that says you cant use both types in one formulation, either.

    Jimbo
     
  5. gonzo
    Joined: Aug 2002
    Posts: 14,132
    Likes: 538, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Demand a written warranty from anyone that sells you a thinner for epoxy
     
  6. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    1) never thin epoxy. Other than a few sellers of just thinned epoxy no one else will recommend it for their products.

    2) thinned epoxy doesn't penetrate any deeper than unthinned into plywood, or solid wood
     
  7. Jimbo1490
    Joined: Jun 2005
    Posts: 785
    Likes: 41, Points: 28, Legacy Rep: 527
    Location: Orlando, FL

    Jimbo1490 Senior Member

    Virtually all commercially available resin systems like WEST use reactive diluents. WEST is made of DGEBPA resin. Yet look at their advertized viscosity: there is no 'pure' BPA resin in existence with viscosity that low; it just does not exist! Search all the data sheets you want but you'll never find a plain BPA resin that thin! They get that low viscosity by adding reactive diluents.

    There is a better way, though: Start with a superior BPF resin. They always have lower viscosity for the same molecular weight. But they do cost more.
     
  8. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Jimbo is correct in that monoepoxides like Heloxy 61 or wetting agents, such as Heloxy 68 will reduce viscosity, with the understanding of what it will do to the cured physical properties of the resin. Some of the physical issues will be tensile strength dropping substantially and water absorption rates rising by as much as 50%.

    The point being misunderstood here is, do you really want to open this can of worms and more importantly do you have an understanding, of the chemical and physical realities thinning epoxy can bring to your project. If some or literally any of this seems over your head, then use the hot on hot method or select a resin system with a lower normal room temperature viscosity.

    The real question here should be why do you want to thin your epoxy? If you think penetration will make a more waterproof surface, you are under a false impression, possably advertising hype derived. Tests have shown that substrate penetration has little bearing on how well a coating waterproofs anything. These same tests concluded that the quality of the coating is what counts, not how deep it penetrates a substrate.

    Lastly, anything that does penetrate plywood will get as far as the first glue line then stop, making the whole penetration issue moot, as the core veneers are still dry.

    Again, why do you want to thin your epoxy?
     
  9. Frog4
    Joined: Oct 2011
    Posts: 150
    Likes: 2, Points: 0, Legacy Rep: 12
    Location: Arizona desert

    Frog4 Proletariat

    a LOT of info to digest in this thread so far thanks for sharing what experience and knowledge you have on this ...

    the "hype" is what I was questioning ... which is why in the OP I requested:

    I wanted to verify all the plywood builder logs I've read where folks swear that's the way to go.

    I need EVIDENCE before I put money, time and energy on something. ..
     
  10. philSweet
    Joined: May 2008
    Posts: 2,273
    Likes: 158, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    If you want to gain some penetration you can heat the wood thirty degrees F by any means you like and apply the epoxy. Keep rolling as the wood cools. I have done this on brightwork that is to get a layer of deck cloth, more epoxy and varnish. After ten years of Florida sun, the epoxy is shot no matter how much varnish you've laid on. If you undercoat, you can lift the old glass off without raising the grain of the plywood. I often add powdered stains or dyes to the undercoat, which probably helps with the release as well. Basically, I do it for the exact opposite of the reason usually given.
     
  11. Frog4
    Joined: Oct 2011
    Posts: 150
    Likes: 2, Points: 0, Legacy Rep: 12
    Location: Arizona desert

    Frog4 Proletariat

    at what temp should I stop heating the plywood? We live in Arizona, high heat is the NORM around here ... ambient temps of 120°F + is easily attained ...
     
  12. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    Frog,

    Take a look at http://www.westsystem.com/ss/thinning-west-system-epoxy/ west details some of the options in how to thin epoxy, and they have a huge collection of studies, testing, and how too guides. Basically they suggest increasing the substrate temp to around 115F and working with room temp epoxy. This gives you the best combination of working time, and penetrating.

    Again though I have never seen any study that indicates deeper penetration has any significant effect on any measurable factor. It doesn't increase bond strength, water proofing, or anything else from what I can find. The only advantage seems to be in vacume infusing, which is an entirely different ball of wax.
     
  13. Frosty

    Frosty Previous Member

    I thinned some epoxy yesterday with acetone and it went foamy and turned into gorila snot. I dont advize it.
    I had to scoop it all out and do it again --
     
  14. JRD
    Joined: May 2010
    Posts: 223
    Likes: 17, Points: 18, Legacy Rep: 192
    Location: New Zealand

    JRD Senior Member

    My understanding is that the penetration through the face grain is much less than originally suggested by the promoters of the technique, but gets the job done by providing a coating rather than actual grain saturation.

    Years ago I used to use Everdure for sealing wood surfaces during refurbishments, at that time not being aware of pure epoxy encapsulation as such.
    Considering the amount of obvious evaporation this appeared to be a very light weight surface sealant compared with three coats of epoxy which seems to be the accepted practice. Arguably the sealing properties of the Everdure may not hold up to what can be achieved using epoxy.

    I am wondering if there is a typical weight of epoxy per square meter (foot) of Gaboon ply to achieve full waterproofing? Obviously this depends on the application method, but ultimately what is the lightest weight that can be achieved and what is the best application method to do this?
     

  15. tunnels

    tunnels Previous Member

    Never thin epoxy BUT you can use a slow hardener so it has lots time to penetrate . It will only go to the first glue line anyway so a thin veneer wont take long to soak . Thick veneers take longer so use slow hardener . Really quite simple !!:confused::D
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.