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Old 11-09-2010, 08:51   #1
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Polyurethane Paint on Epoxy

Hi folks,

I am building a fridge. Inside box is 12 mm plywood.
I have sanded it and put 3 layers of west system epoxy (105/206) on it, 3 layers wet in wet. Turned into a beautiful flat and shiny surface. Then cleaned it with solvent, sanded it to a frosty appearance with 150 grid and cleaned it again. Like it says on the tin I put a first layer of Easypoxy paint on it. No primer.
Point is now that this is 36 hours ago and the paint is still sticky.
Is this normal for polyurethane paint on epoxy?

Any thoughts?

Thanks, Len.
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Old 11-09-2010, 09:19   #2
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NO, it is not normal. Under average conditions, if mixed correctly, LPU is dry to the touch in about 3hrs.
That is with the paint systems of DuPont, Interlux and Awlgrip. Not familiar with your product combinations.
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Old 11-09-2010, 09:52   #3
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Just so others know Len, Easypoxy is not an epoxy, which of course uses two parts. Easypoxy is a one-part polyurethane paint.

This is not normal for it to not have cured by now. Other than very high humidity, too cold a temperature, not mixing it thoroughly or using the wrong reducer, I cannot imagine what would prevent it from drying by now. You may just have a bad batch of paint.
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Old 11-09-2010, 10:21   #4
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Well, thanks for your time.

Can't imagine there was anything wrong with the paint.
Used a brushing thinner like it says on the tin.
Didn't buy the Easypoxy brushing thinner though. Used what I had.
I painted another surface with this mixture as a test and that was/is 100% ok.....

So it looks to me the direct contact with the epoxy surface has something to do with it... Maybe a primer would have helped here. Well, I guess/sure hope it will dry eventually....

If it dries, I'll put on the second layer without the thinner and see how that goes. If it doesn't I guess I'll try to put a primer on the sticky layer first, to close it off.

I'll "report" about the final result here, maybe there is a soul on this earth who could benefit from it.

Cheers, Len.
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Old 11-09-2010, 13:42   #5
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Painting with Easypoxy

Hi, I have painted with Easypoxy with great success. I believe that where you went
wrong was not using a primer. Your thinner (not all are alike) may not have been compatable with
the Easypoxy. I do not think that putting another coat over a bad one is a good idea.
I would use a thinner (try Lacquer) and try to wipe off the first coat, then sand and start fresh.
Make sure that you do not have any contaminents on the surface. It must be free
of all grease, body lotion/hand lotion etc. You can then wipe the surface down with
denatured alcohol and then use a tac cloth for use with an epoxy paint not a regular
tac cloth. Make sure that your primer is one that is compatable with easypoxy. The prep work has everything to do with a good durable paint job! Good Luck, CC
Quote:
Originally Posted by svpresent View Post
Well, thanks for your time.

Can't imagine there was anything wrong with the paint.
Used a brushing thinner like it says on the tin.
Didn't buy the Easypoxy brushing thinner though. Used what I had.
I painted another surface with this mixture as a test and that was/is 100% ok.....

So it looks to me the direct contact with the epoxy surface has something to do with it... Maybe a primer would have helped here. Well, I guess/sure hope it will dry eventually....

If it dries, I'll put on the second layer without the thinner and see how that goes. If it doesn't I guess I'll try to put a primer on the sticky layer first, to close it off.

I'll "report" about the final result here, maybe there is a soul on this earth who could benefit from it.

Cheers, Len.
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Old 11-09-2010, 15:31   #6
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If you are painting inside an enclosed box with no ventilation you are not letting the solvent evaporate from the paint so it will dry. The solvents will stay inside the box inhibiting dying and further evaporation. Try putting a small fan blowing in the box see if that helps.

Good luck
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Old 11-09-2010, 16:47   #7
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Quote:
Originally Posted by sailvayu View Post
If you are painting inside an enclosed box with no ventilation you are not letting the solvent evaporate from the paint so it will dry. The solvents will stay inside the box inhibiting dying and further evaporation. Try putting a small fan blowing in the box see if that helps.

Good luck
Careful with those vapors and that fan motor. Source of ignition.
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Old 11-09-2010, 21:05   #8
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Pot luck...

I'm doing all the interior woodwork in Boracay by priming with thinned epoxy resin and then topcoating with marine polyurethane varnish.

Once or twice the varnish just did not dry. Other times I've gotten on "orange peel" or star" effect which has been annoying, but mostly only on small areas and not enough to redo the job.

For the current batch of varnishings one small piece has it quite bad and there are a few other patches.

From what I can work out it's related to how well the epoxy sets. The thinner slows the setting and if it does not evaporate completely, hey presto, instant "orange peel".

I've also found that the epoxy that I use can be very slow to set under 15 degrees Celsius.

So my guess is that your epoxy may not have fully set, the solvent in the paint has got into the epoxy and the whole lot has decided that they don't like you.

If it were me I'd try to keep the whole lot nice and warm for as long as it takes to set. [Cautions above apply - leaving in the sun could be best.]

The sticky polyurethane varnish that I had never really set. It was on the sole so I just walked on it till it wore off.

So the suggestion about cleaning it off with solvent could have some merit, though I'd try leaving it in the sun first.
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Old 12-09-2010, 06:52   #9
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A lot of epoxies develope a "bloom" after curing which will prohibit adhesion of another product. It should be washed with water and a scrubbie rather than a solvent. Also most epoxies take a week to fully cure. Either of these scenarios could be causing your problems. I've built a couple wood/epoxy dinghies and have used epoxy for repairs on my sailboat prior to using polyurethanes and never had a problem with the above concerns in mind. I've used Easypoxy too and like it for lockers and such. Best of luck!
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Old 12-09-2010, 07:03   #10
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I would call the West guys and talk to them, it is probably the epoxy not the paint.

Boracay: What are you using to thin the epoxy? I use full strength epoxy as a sealant. It is generally fine applied neat with a brush.
If you want it to soak in heat the wood then let it cool after the epoxy is applied.
I generally just use a heat gun for a minute or so, or do it out in the sun, and the epoxy soaks right in.
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Old 12-09-2010, 12:02   #11
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WEST System epoxy develops an amine “blush”, as Shoalcove noted.

As David M notes, Pettit “Easypoxy” is a one-part polyurethane enamel paint with silicone & ultraviolet filters.

The drying time is 1-1/2 → 6 hours “to touch” and 8 → 24 hours “to overcoat”.

“Bare wood that has been epoxied must be thoroughly scrubbed with an ammonia/water solution then sanded with 120 grit paper and solvent cleaned.
Follow with a coat of 4172/4027 Polypoxy White Undercoater to smooth the surface and provide a uniform base; sand well and solvent clean then proceed with the first coat of Easypoxy.”


See ➥ http://www.pettitpaint.com/fileshare.../easyproxy.pdf
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Old 12-09-2010, 12:59   #12
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For the inside of a frige or any wet locker / damp area... a 1 OR 2 part LP paint is not to be used. (IE Awlgrip) All of my boats have had a 2 part LP paint, and if for example you lay a vinyl boat cushion on the deck for 2 months, the paint will blister up under the cushion. It can take solvents, but not H2O up against it & kept there. The best for your box is after the glass / epoxy work is done, coat on 3 sucessive coats of white pigmented WEST epoxy as carefully as possible, and with the pot, stir stick, interrior & brush dust free. This will leave a shiney, easy to clean, water vapor proof surface, that will never be a problem. Our frige & wet lockers have held up for 15 years this way. Mark
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Old 12-09-2010, 13:09   #13
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oops! By virtue of being only 2 cu/ft and being insulated = to 7+ inches thick, with both foam & vacuum panels. Refrigeration can be gotten down to about 25 A/H per day. The "gel coat" has held up perfectly. M
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Old 12-09-2010, 13:37   #14
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Nice job Mark! I agree that polyurethane isn't the best choice for a spot that may have continuous immersion (such as melted ice). Gord's correct of course, the term is blush not bloom but the effect is the same That's the trouble with posting after working most of the night!
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Old 13-09-2010, 10:13   #15
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Thanks to all for your responses.
I contacted West Systems and this was their advice.

Len:
The epoxy may have been a bit under-cured for the polyurethane to dry well. Epoxy hardener chemistry, if not fully reacted with epoxy resin, will cause one-part polyurethane dryers to be ineffective. The way you avoid the problem is allow the epoxy to cure for several days (so the epoxy is further reacted) or apply a primer first as primers are less sensitive to interacting with the surface chemistry. A water wash is always recommended to remove residual hardener components prior to sanding and applying paint. Solvents are less effective for this.

For your situation, I would remove the Easypoxy with lacquer thinner, wet sand the surface with water & wet/dry sandpaper and try applying the Easypoxy again in a small spot to be sure it sets up fine. I believe it will. If not, I suggest you apply a good sandable primer prior to applying the Easypoxy.

Feel free to call me or e-mail back with questions. Our toll free number is 866-937-8797.

Best regards,

Tom Pawlak

Technical Service
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