Understanding Wax and Polyester Laminating Resin?

Discussion in 'Materials' started by Jeff in Boston, May 11, 2021.

  1. Jeff in Boston
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    Jeff in Boston Junior Member

    So, my understanding of multi layer polyester laminations in a mold is that the final layer needs wax or another air barrier to cure.

    But how exactly does that work with wax? You mix it in. Does it then float to the top to form a barrier?

    Buuuut.... you also use wax as a release agent in the mold. Why doesn't that wax cause the first layer to cure?
     
  2. Rumars
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    Rumars Senior Member

    Yes, the wax does nothing chemically, it just creates a physical barrier between the laminate surface and the oxigen in the air. It does this because it's soluble in styrene, and when the styrene evaporates the wax returns into a solid state, forming a film on the surface. You can create the same effect by spraying PVA or covering the laminate with a piece of plastic.
    The oxigen only retards the surface it touches, the rest of the laminate cures normally, the parts in contact with the mold are already cured by the time you get to the last layer. We use this effect when laminating to our advantage, we control the amount of material that cures (important for heat distortion) while the surface remains uncured and bonds chemically to the next layer.
     
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  3. Jeff in Boston
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    Jeff in Boston Junior Member

    The concept that only the top layer is uncured makes sense. Thanks.

    But why doesn't the styrene on the first layer dissolve the wax on the mold?
     
  4. Blueknarr
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    Blueknarr Senior Member

    Mold wax is partially dissolved.
    But it takes time to fully dissolve. The resin cures faster than the mold wax can be dissolved.

    The surfacing wax is pre-disolved before it is added to the resin.
     
  5. Rumars
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    Rumars Senior Member

    Styrene migration is a danger, especially with new molds or high styrene content resins, so a PVA barrier is sometimes recommended. But basicly the used wax formulations, in the recommended thickness, resist the solvent long enough to allow demolding.
     
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  6. Mr Efficiency
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    Mr Efficiency Senior Member

    The "final layer" is usually a pigmented, waxed resin, I don't think many people mix wax into resin. In any case, unwaxed resin laminate will eventually lose its tack.
     
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  7. Jeff in Boston
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    Jeff in Boston Junior Member

    Thanks everyone! That helps!
     

  8. ondarvr
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    ondarvr Senior Member

    As a rule, never buy gel coat or resin with wax already in it, always get it without wax and then add it yourself when needed.

    This makes what you buy far more versatile in how you can use it.
     
    Last edited: May 12, 2021
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