Epoxy over laminating polyester.

Discussion in 'Materials' started by Canracer, Sep 3, 2016.

  1. Canracer
    Joined: Aug 2009
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    Canracer Senior Member

    I'm getting my kayak project up and running.

    Will epoxy adhere to laminating polyester? The poly cured for a long time and it's still tacky to the touch. That's the nature of laminating poly (right?) so I'm not concerned about that.

    I plan to continue the laminate with epoxy, will will it stick well to the tackiness?
     
  2. upchurchmr
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    upchurchmr Senior Member

    Why do you want to laminate with two different resins?

    Is this a solid glass boat or a strip planked boat?

    Polyester should cure solid, or all the fiberglass boats in the world would be sticky.
     
  3. Canracer
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    Canracer Senior Member

    My understanding is that "laminating" polyester does not fully cure on the surface. This allows the next layer to be applied and then create a full chemical bond. The non-laminating formulation includes a type of wax that migrates to the surface and blocks the oxygen. Deprived of oxygen, the polyester will fully cure.
     
  4. Canracer
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    Canracer Senior Member

  5. ondarvr
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    ondarvr Senior Member

    Polyesters stay sticky for a while, but typically become tack free over time. For the epoxy to bond the polyester will need to be fully cured and sanded.

    What was the link for, it didn't seem to relate to this subject at all?
     
  6. Canracer
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    Canracer Senior Member

  7. Mr Efficiency
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    Mr Efficiency Senior Member

    So what is the purpose of switching to epoxy ?
     
  8. gonzo
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    gonzo Senior Member

    Is it only slightly tacky, but hard? You can clean it with a solvent and try waxed resin or gelcoat to promote complete curing.
     
  9. Canracer
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    Canracer Senior Member

    It's cured well and the laminate is fairly tough. But the surface is a little tacky.
     
  10. SailorTom
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    SailorTom New Member

    Laminating polyester will stay tacky indefinitely if not deprived of O2. I have a 47 year old Luger Leeward kit that I'm now building. The bench seats are still tacky on the backside, not gel coated side. I suspect laminating polyester since these have been stored in doors, basically untouched since new for all these years. When I get time and think about it, I'll cover it with saran wrap and see if the top layer kicks.

    According to my books and experience epoxy will adhere very well to polyester. They only real issue is polyester gel coat will not adhere to epoxy and CSM binders will not dissolve in the resin so it's less flexible.

    Suggest you find the West Systems Epoxy book or Raka Epoxy book online.
     
  11. abourgault
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    abourgault Junior Member

    If you spray PVA (polyvinyl alcool) over the tacky polyester it should fully cure. After it's cured, clean with water.
     
  12. mydauphin
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    mydauphin Senior Member

    Paint over with a coat of hot polystyrene resin, non laminating. What I mean by hot is one with more mek than usual. Then stick it out in the sun for a few days, sand and recoat with epoxy. I do this with holding tanks inside and out, makes them less pours. Regular resin absorbs moisture, epoxy doesnot. But beware of Epoxy and uv.
     
  13. ondarvr
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    ondarvr Senior Member

    At this point spraying PVA or putting Saran wrap over old sticky resin won't help it cure, these steps need to be done during the initial cure cycle to work well. Some resins will stay sticky for a long time, some due to the type of base resin, others due to being under or over catalyzed when first used.

    For a "hot coat" the catalyst level should never exceed the amount recommended for that exact resin, adding more can actually extend the gel time and significantly reduce the physical properties of the resin.
     
  14. ondarvr
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    ondarvr Senior Member

    You still haven't said what you're exaclty doing.

    The glass section you epoxied into the hull looked like there were large areas that weren't bonded to the hull.

    Using just cloth with polyester resin typically results in a poor bond, it will frequently peel off easily, CSM should be used under the first layer, and between each layer.
     

  15. Canracer
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    Canracer Senior Member

    There are 6 video episodes to the project. If you open a link, you should be able to see a link to my youtube channel. All the episodes are there, I demonstrated how the glass was adhered to the kayak.

    This is a link to the full channel. https://www.youtube.com/user/coffeefish/videos
     
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