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Old 03-03-2010, 08:35   #1
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Pigmented Epoxy Resin Instead of Painting?

When I restored my Pearson Triton nine years ago, I stiffened the cockpit sole by fiberglassing some plywood to top the cockpit sole. I then laid down a couple of layers of fiberglass cloth over the plywood. It turned out pretty good (no flex and solid underfoot), but apparently I didn't prep the surface correctly before painting because the paint started to come off in places a couple of years ago. I am going to take off the old paint and was planning on painting it again, but then started thinking about something.

Epoxy resin, if left exposed to the sun, will deteriorate (which is why you paint it). But what if you mixed a white pigment into the resin before brushing on the final coat? Would that be enough to protect it? After all, isn't gelcoat just pigmented polyester resin? And it doesn't need painting.

Thanks in advance for your thoughts on this.
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Old 03-03-2010, 11:41   #2
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UV is what degrades epoxy and mixing pigment that didn't interfere with the chemical properties (if there is such a thing) would still expose the epoxy to UV.
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Old 03-03-2010, 11:55   #3
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Also, consider mechanical properties of epoxies vs. e.g. polyurethanes.

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Old 03-03-2010, 11:59   #4
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Mixing pigment into epoxy makes epoxy paint. I've done the same with polyester resin with good results.
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Old 03-03-2010, 12:17   #5
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The epoxy will still degrade from UV with pigment. If you used West System or the likes, it dries with an amine blush which must be removed before it can be re-coated and if you don't remove it all, nothing, even additional epoxy will stick. A thorough scrubbing with soap and water and a 3M pad will remove the blush, but you then will need to sand it no matter what you re-coat with. So why not get it to this point and just repaint it rather than starting all over again. WG
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Old 03-03-2010, 13:47   #6
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Oh no, with enough pigment added, you made yourself an epoxy gelcoat that withstands UV just as well as polyester gelcoat.

All gelcoats and all paints are degraded by UV. If pigmented, this degradation works slowly by eroding the outer surface, while the rest of the coat is protected by the pigment on top. A clear coating (like varnish) doesn't have that protection and they use UV inhibitors that absorb the UV radiation until they are end-of-life.
Very good paint systems like Awlgrip might use UV inhibitors in addition to pigment. When you make your own epoxy gelcoat you can do the same by using the hardener (West System) with UV inhibitor.

West System has a document / test on their website that shows the above.

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Old 03-03-2010, 14:09   #7
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All confused

To be able to help you out on this one please state:

The glassing was it done with Epoxy or polyester?

The rule as I have learned it is that epoxy over polyester ( cured ) is OK but the other way around is a no go.( Except system three´s special products)

If you have an all epoxy layup I would advise in epoxy with pigments suited for the system and finally a polyurethane two pack product with really good UV protection properties in a multilayer layup.

Rgds

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Old 03-03-2010, 14:12   #8
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I mixed pigment into my final two coats of resin when I built a spare rudder last spring. U.S. composites has pigment as well as everything else you could need for the project.
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Old 03-03-2010, 14:13   #9
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Colored Pigments
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Old 03-03-2010, 16:02   #10
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Yes, I was a bit incomplete with my post... gelcoat doesn't hold up well against UV; Jedi is shedding her gelcoat so fast that I can look through it at spots. Everytime you polish it, you remove the degraded (powdery) outer layer and UV does it's thing with the fresh exposed material.

So painting it is always the best option. I am no expert on that but for a cockpit sole I would think some anti-slip properties are also required? I would even consider Treadmaster.

The West System document is here: WEST SYSTEM - Projects - Adding pigments to epoxy

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Old 07-03-2010, 21:12   #11
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Read the document. Epoxy pigments do not provide UV filtering. The next to last graph sum that up:
"It is important to realize, however, that while pigmented epoxy may be somewhat more UV resistant than unpigmented epoxy, pigmented epoxy should still be covered with a UV resistant coating, either clear coat or paint, to protect it from UV radiation for outdoor applications. "
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Old 07-03-2010, 21:55   #12
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Hi David, I think you missed my post #10 in this thread where I accept the wisdom of the protection of paint.

ciao!
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Old 08-03-2010, 05:39   #13
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Thanks for the responses. After doing a little more research, I came to the same conclusions. So, I'm just going to paint and not worry about adding pigment.
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Old 08-03-2010, 06:38   #14
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Do not forget to wet sand it first, making sure every little patch and corner is sanded, flushed and scrubbed (scotchpad) and flushed again. You need to get rid of all the amine blush.

Next project, mix some white pigment through the epoxy for the final coat and paint afterward. You can use up to 5% pigment (in weight) without affecting the strength of the epoxy and this helps for the pain job plus provides temporary UV protection for the time in between.

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Old 20-03-2010, 14:27   #15
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I have been playing with pigmented epoxy recently and the finish is as nice as gelcoat except its a moisture sealer as well. But I know UV will deal to it eventually. Have talked to various boat builders and boaties, one point thats worth mentioning is that gelcoat is far more durable than paint, it wont peel off easy and you can drop things on it without much damage(within reason). Gelcoat polishes well and looks good, it does seem to have a little more strength than paint as well.
Paint is chosen for ease of use, but for durability, gelcoat is the choice. So if we can seal or repair with epoxy, and prepare it well so that gelcoat can adhere...would be the ultimate. Gelcoat stands UV better than paints, if a thick layer is applied it can be polished for a very long time. Try polishing and/sanding paint!!, and 2 pot paint is not cheap either.
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