PVA + Gelcoat in mould, for adhesion to epoxy laminate

Discussion in 'Materials' started by idkfa, Dec 20, 2016.

  1. idkfa
    Joined: Sep 2005
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    Location: Windward islands, Caribbean

    idkfa Senior Member

    Since epoxy is used to bond polyester parts together... Epoxy laminate over gelcoat in mould should be fine.

    But it isnt,

    Unwaxed gelcoat is used in moulds, so the surface cures very slowly, presenting ready bond for polyester laminate...

    Waxed gelcoat in a mould will cure, in hrs... but then there is wax inhibiting laminate bond....

    What if PVA is used over the gelcoat... it will fully cure, allowing for good adhesion to epoxy laminate????...with some light sanding to key surface.
     
  2. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    And...you need to wash the PVA off with water, then sand.

    There are epoxy compatible gel coats.
     
  3. idkfa
    Joined: Sep 2005
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    Location: Windward islands, Caribbean

    idkfa Senior Member

    Guess I'm testing the premise that chemically gelcoat is coloured, thickened polyester resin....

    Cause all polyester laminates are compatible with epoxy.... if surface preped correctly...

    Then all gelcoats are also compatible with epoxy....

    In a commerical setting, no one is going to PVA-sand or use peelply...Hence the "compatibility" problems.

    But for smaller parts PVA is an option. Tks
     
  4. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    What I'm saying is that while yes it could be done, there are much easier ways to get a gel coat finish on an epoxy part.

    Duratec products are designed for this type of application, they cure tack free for in-mold use with epoxy (they work with Polyester and VE too).
     

  5. Jim Caldwell
    Joined: Aug 2013
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    Location: Cleveland, Ohio

    Jim Caldwell Senior Member

    I was told epoxy only bonds well to old polyester products as in no strine smell.
     
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