painting plastic

Discussion in 'Materials' started by Tungsten, Oct 25, 2015.

  1. Tungsten
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    Tungsten Senior Member

  2. PAR
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    PAR Yacht Designer/Builder

    These are polycarbonate (I think) and take paint pretty well, though the "etching" stuff designed for plastics will stick better. All the major formulators sell a plastic specific paint.
     
  3. kapnD
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    kapnD Senior Member

    On the same subject, I'm installing polycarbonate windows with doublestickytape and silicone caulking, would like to paint the backside border of the windows black first so the stickystuff doesn't show, as well as to protect the adhesives from UV damage.
    I bought some spray paint that is specific for plastic, but I am concerned that the paint layer will be a weak point in the bonding.
    Prepping the surfaced with acetone takes the gloss off the plastic, is this equivalent to the "etching" product?
    Am I overthinking this?
     
  4. PAR
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    PAR Yacht Designer/Builder

    Taking the gloss off, might not be the same as etching, but it probably is. I too would be concerned about the quality of the bond, so a simple test might do. A scrap of glazing and two areas, one with the paint and goo and one without. Test the peel strength in a few weeks after the goo has had plenty of time to cure. The sure fire way is to paint the outside of the glazing, letting the goo have it's way with the unmolested inside.
     
  5. Tungsten
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    Tungsten Senior Member

    Well no luck on the first try,cant remember brand but was primer for plastic.Will try thr fusion plastic paint next with no primer.
    xylene doesn't seem to do anything to the surface but it evaporates so quickly its hard to tell.I do have some xylene based primer ill give that a shot.

    Whats a good way to test the peel strength?Everything Ive done so far comes off easily with a finger nail.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    You can test peel strength by scratching a cross into the painted surface, with for example a box cutter, then apply some masking tape, and rip off. But paints develop adhesion over days or weeks in some instances, so premature testing may not be the best guide.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    There are available certain types of acrylic paint that will stick to ceramic tiles and other slick surfaces, I am surprised how well it does adhere, but that ain't plastic, of course.
     
  8. PAR
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    PAR Yacht Designer/Builder

    Check out the MSD sheet over at Krylon and see what the vehicle(s) are in their Fusion paint. This will give you a clue as to what they're using to attack the plastic, prior to the resin setting up. Not a surprise about xylene - it's not aggressive enough on hard plastics, though pretty effective on soft ones. I'll bet on acetone and toluene as the primary butt kickers, with some likely acetone related derivatives tossed in for good measure. I can make a phone call tomorrow and find out.
     
  9. Tungsten
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    Tungsten Senior Member

    My concern is over time the paint will flake off,temp swings from winter to summer are huge around here and then there's the pressure washer every spring to remove dirt that gets trapped on the panel overlaps.

    Vynal wrap or colored tape of some sort might be the only way,or just forget about it and that's the color they are.

    Thanks for the help.
     

  10. PAR
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    PAR Yacht Designer/Builder

    If you're really worried about the bond, paint or vinyl wrap the outside, to insure your sealant has as good a grip as possible. This is what I would do and is one of the compromises you just need to accept sometimes. Then again, you could consider some sort of mechanical lock, like a glazing perimeter channel that is glued and or hard fastened to the cabin sides. I made a set of acrylic lights once with an extra wide rabbet. The goo line was taped off on the glazing (both sides) and the buttered up stock lowered into the rabbet, knowing lots of ooze out would squeeze around the edges, filling the rabbet and surrounding the glazing edges. When it was cured, I razored off the ooze out, at the tape line and had a clean, neat install.
     
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