2 part polyurethane foam as adhesive to blue foam

Discussion in 'Materials' started by Resurrection, Jun 1, 2019.

  1. Resurrection
    Joined: Apr 2017
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    Resurrection Junior Member

    Gentlemen,
    Does anyone know if a 2 part high density polyurethane pour foam ( 6 or 8 lb density ) will bond to Dow extruded polystyrene bouyancy billets without melting it when curing?
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Shouldn't be a problem, but keeping the foam billets in place when you pour the foam around them might be.
     
  3. Resurrection
    Joined: Apr 2017
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    Resurrection Junior Member

    Thanks Mr Efficiency.
    I'm thinking of cutting sections of the blue foam to fit loosely into pre-made fiberglass crossbeams under the deck (each having an open top . Literally just flat sheets of pre-made 1708 cut and laid in vertically from the hull up to what will be the bottom of the deck ) ; maybe with a 1/4 in gap all around.
    I'd use the higher density expanding foam to solidly bond the XPS to the hull and crossbeams filling in any cavities .
    I also want to cover the top with the 2-part then glass over it.
    I intend to use vinyl ester resin which I know would melt the blue foam but not the polyurethane foam.
    After watching some videos of the foam kicking off I know there's only about 1 minute give or take after mixing before it starts to react and expand.
    I'm thinking I could "speed paint" the bottom and walls of each section before sticking the blue foam in place, then weighting it down before it kicks.
    Would this work?
     
  4. JamesG123
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    JamesG123 Senior Member

    That seems convoluted. Are you just trying to use up some blue foam scrap as filler?
     
  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Glassing xps for what purpose?

    You aren't gonna walk on it. Even under the deck; it will move and flex and delam.

    It has no shear whatsoever. This panel was built without any surface abrasion as a test. It had peelply removed and the careful peelply removal resulted in edge delamination. The peel test was similar to removing a paper backing from a sticker.

    562D50D7-BA10-40AC-A94F-C7D5F3744F87.jpeg

    If you are trying to build floor stiffeners; use marine foam offcuts.

    These are ultralight. Super stiff. Take a day to glue and another day to laminate a piece of glass each side. Might build in one day with fast epoxies.

    C8AFB6B2-A4CD-463B-89BE-11DC087FCC4B.jpeg
     
  6. Resurrection
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    Resurrection Junior Member

    Thanks Fallguy,
    Primarily I want the extruded polystyrene as floatation NOT for structural purposes.
    After having pulled out all of the very waterlogged lightweight blown-in foam and reading enough horror stories of soaked foam removal from others, I will NOT use any two part foam as floatation.
    The old foam did, however, maintain a pretty tenacious grip to the hull and glassed in stringers so I'm thinking that a thin outer layer of this stuff in a heavier density might do a few things:
    1) bond the foam to the hull and verticle sections ( after scoring foam surfaces [ thanks Fallguy ] )
    2) provide a buffer against vibration and delamination ( ? )
    3) provide a surface on top that can be glassed to without melting, using vinyl ester resin

    Finally, I would lay a rigid composite deck on top. So in this scheme, the verticle sections; stringers and crossmembers made of 1708 & CSM, would bear the verticle loads through the hull and from the deck . The blue foam would be isolated from any direct loading.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Using high density PU will largely eliminate the problem of foam breakdown and water absorption, I take it the OP wants to pad-out the space with cheaper and lighter material, but it might be difficult to have it all end up where you want it, best to try a small section first and see how it goes. Remember though that you can do it in small pours, you don't have to complete the filling in one pour, even of a small section. The new pour will stick to the old pretty well.
     
  8. Resurrection
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    Resurrection Junior Member

    Thanks Mr E,
     
  9. fallguy
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    fallguy Senior Member

    I think the older foams were not as good, so I would not distrust pour foams.
     
  10. Resurrection
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    Resurrection Junior Member

    You might be right Fall Guy.
    The foam I dug out was pretty lightweight and didn't seem to me to be very closed cell in it's makeup. The whole experience left a bad taste toward lightweight urethane pour in's.
    I'm pretty sure the extruded polystyrene is pretty much entirely impervious to water absorption so I've been trying to figure out a good way to use it without relying on it for anything structural even though it also comes in different densities.
    The boat might be seeing extended time in the water so just in case ...
     
  11. Steve Clark
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    Steve Clark Charged Particle

    Gorilla Glue works a treat. You can make it foamier by mixing in a bit of water.
    EPS isn’t particularly brilliant with regards to water absorption. I think it is in the 1-2% porosity by volume league.
    Which can be a lot of water.
    I always try to keep it out of the bilge and paint it with epoxy floor paint.
    SHC
     
  12. upchurchmr
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    upchurchmr Senior Member

    Did I get this right? You want to use blue foam for flotation and want to attach it to the deck?

    For it to provide the flotation, the entire boat would have to be full of water.

    Am I completely off base?
     
  13. Resurrection
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    Resurrection Junior Member

    Steve,
    Thanks. I may use some "normal" adhesive for different applications in this build but I'd want something that could be used below the waterline. 3M 5200 or Plexus maybe.
     
  14. Resurrection
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    Resurrection Junior Member

    Now that would be an odd thing !
    UNDER the deck for safety floatation and as non load bearing forms to glass over to make structural load bearing members
     

  15. gonzo
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    gonzo Senior Member

    Under the deck is not a very effective location for reserve buoyancy. It would only work when the boat is completely submerged. Ideally you should place it lower.
     
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