How to seal XPS or EPS?

Discussion in 'Materials' started by MassimilianoPorta, Feb 17, 2020.

  1. MassimilianoPorta
    Joined: Apr 2019
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    MassimilianoPorta Junior Member

    Hi,
    what is the easiest/cheapest way to seal an XPS or EPS surface so it can be used with a polyester resin without dissolving the foam?
     
  2. dinoa
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    dinoa Senior Member

    Acrylic emulsion paint
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    There is a polyester than can be used with polystyrene foam these days, you might find it in the Duratec line-up. Maybe once coated, revert to normal polyester. Member Ondarvr here would be your best guide to that.
     
  4. MassimilianoPorta
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    MassimilianoPorta Junior Member

    Thanks, I will give it a try
     
  5. MassimilianoPorta
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    MassimilianoPorta Junior Member

    Unfortunately it looks like I cannot find any Duratec product in Italy :-(
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    ►Polystyrene Compatible Resins
    Tricel Composites offer a polyester resin that can be used directly on the polystyrene block, or sheet, without attacking the surface.
     
  7. MassimilianoPorta
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    MassimilianoPorta Junior Member

    Will have a look, thank you
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I think if you make enquiries with local suppliers, you may find a compatible polyester of some kind, I guess it then becomes a question of whether you have to use that particular resin, or ordinary polyester will be compatible with the sealing one, for further lamination.
     
  9. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Papier-mâché made with PVA glue will work.
    The special polyester resin made for xps usually costs about the same as epoxy.
    You might consider using PU foam instead of XPS.
     
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  10. MassimilianoPorta
    Joined: Apr 2019
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    MassimilianoPorta Junior Member

    I will give acrylic emulsion paint a try, if unsuccessful I will try other methods

    Thank you for suggesting
     
  11. philSweet
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    philSweet Senior Member

    The easiest, simplest and cheapest is to use epoxy. It doesn't cost any more than decent polyester resin.
     
  12. antonkov
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    antonkov Junior Member

  13. MassimilianoPorta
    Joined: Apr 2019
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    MassimilianoPorta Junior Member

    Thank you, interesting!
    So far I have not been lucky with acrylic paint so the only way I found to work on my plug has been to coat with a light film of epoxy, then apply polyester pattern making gelcoat and... a lot of sanding:rolleyes:
    Something I will try on the next plug will be to add some very light glass with the epoxy, just to have a little more hard surface for the successive coatings
     
  14. antonkov
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    antonkov Junior Member

    i am using waterbased primer (bull eye 1-2-3 or glidden gripper) to adhere to the foam, then drywall compound for fairing, then thin, infusion grade epoxy over the sanded compound as a barrier. this is quick and cheap method and sanding needs some care as the layer of primer is barely harder than the compound. in plans is to try Eplison EPS Foam Coating, which is an epoxy specifically designed for the task, hoping it will both replace the layer of traditional light glass an provide a styrol barrier
     

  15. MassimilianoPorta
    Joined: Apr 2019
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    MassimilianoPorta Junior Member

    I more or less did as you, but just infusion epoxy and then normal polyester putty to take advantage of the super fast cure time.
    I want to try to add 25 gr sqm glass just to provide a little more scratch resistance
    Thank you for sharing your method!
     
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