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Polyurethane and tacky epoxy

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doub...@hotmail.com

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Jun 23, 2007, 9:23:54 AM6/23/07
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Has anyone tried or know what would happen if you applied a
polyurethane product over epoxy when the epoxy was still tacky. Would
the adhesion be better? Would it intefere with the cure of the epoxy?
What about a latex primer over sticky epoxy? Anyone try anything like
that to try and get a better adhesion to the epoxy?

TIA,

Bob

Bruce

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Jun 23, 2007, 10:14:30 AM6/23/07
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I once tried that trick with coal-tar epoxy and copper anti-fouling.
Cleaned the propeller real well and applied coal-tar epoxy. Waited
until it got tacky and slathered on the copper based paint. The next
trip most of the paint came off, just like it always does.

As far as I can tell there is no problem in making paint stick to
epoxy.I usually make sure that any blush is cleaned off the epoxy and
then fill, fair and prime with epoxy based materials and apply a top
coat of two part polyurethane. My sloop is going on ten years now and
still looks pretty good.


Bruce in Bangkok
(brucepaigeatgmaildotcom)

--
Posted via a free Usenet account from http://www.teranews.com

Lodewijk Stegman

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Jun 23, 2007, 6:26:55 PM6/23/07
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doub...@hotmail.com schreef in news:1182605034.890782.50700
@m36g2000hse.googlegroups.com

I have never tried it, for the reason that my local vendor warns against
doing this. They even claim that is wise not to paint epoxy before it is
fully (and I mean FULLY) cured. That can take up to a week, depending on
temperature and formulation of the epoxy.

Adding another coat, before the previous coat is not fully cured, works
great for the adhesion between coats of epoxy, but not between epoxy and
something else.

--
Lodewijk

justwaitaf...@gmail.com

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Jun 23, 2007, 7:27:32 PM6/23/07
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On Jun 23, 6:26 pm, Lodewijk Stegman <ajeevee-ditwegha...@xs4all.nl>
wrote:
> doubl...@hotmail.com schreef in news:1182605034.890782.50700

I laid some marine enamel down once on tacky epoxy, forget the brand,
but it made a great bond. But note it was pure luck because in other
attempts to do this in uncontrolled environment led to major peeling.
I think the best way to go is "traditional", washing the surface,
roughing it up, and depending on a mechanical bond. Just my opinion.

Paul Oman

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Jun 24, 2007, 4:31:46 PM6/24/07
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justwaitaf...@gmail.com wrote:

>On Jun 23, 6:26 pm, Lodewijk Stegman <ajeevee-ditwegha...@xs4all.nl>
>wrote:
>
>
>>doubl...@hotmail.com schreef in news:1182605034.890782.50700
>>@m36g2000hse.googlegroups.com
>>
>>
>>
>>>Has anyone tried or know what would happen if you applied a
>>>polyurethane product over epoxy when the epoxy was still tacky. Would
>>>the adhesion be better? Would it intefere with the cure of the epoxy?
>>>What about a latex primer over sticky epoxy? Anyone try anything like
>>>that to try and get a better adhesion to the epoxy?
>>>
>>>
>>I have never tried it, for the reason that my local vendor warns against
>>doing this. They even claim that is wise not to paint epoxy before it is
>>fully (and I mean FULLY) cured. That can take up to a week, depending on
>>temperature and formulation of the epoxy.
>>
>>

>-------------------
>
>

We have put wet latex over wet epoxy (epoxy that was mixed minutes
before). If it is a top epoxy you get a perfect finish, of course you
cannot brush the latex paint on....

folks usually wait a bit past tacky (but still soft enough to put your
thumbnail into the epoxy).

Actually epoxies take about a week to fully cure, so if you have
topcoated epoxy in less than a week, you've actually painted over not
fully cured epoxy anyway. At least in theory, the coating fuse and you
get a chemical as well as a mechanical bond.

paul oman
progressive epoxy polymers inc
www.epoxyproducts.com/marine.html

cavelamb himself

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Jun 24, 2007, 4:40:38 PM6/24/07
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Paul Oman wrote:
>
> We have put wet latex over wet epoxy (epoxy that was mixed minutes
> before). If it is a top epoxy you get a perfect finish, of course you
> cannot brush the latex paint on....
>
> folks usually wait a bit past tacky (but still soft enough to put your
> thumbnail into the epoxy).
>
> Actually epoxies take about a week to fully cure, so if you have
> topcoated epoxy in less than a week, you've actually painted over not
> fully cured epoxy anyway. At least in theory, the coating fuse and you
> get a chemical as well as a mechanical bond.
>

provided, of course, that no surface blush has developed...

Paul Oman

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Jun 24, 2007, 4:48:10 PM6/24/07
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cavelamb himself wrote:

--- that's true, but the good epoxies generally don't blush --- paul

doub...@hotmail.com

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Jun 28, 2007, 7:49:16 AM6/28/07
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Thanks guys. I guess I'll let it cure first. I was hoping to avoid
sanding because the sanding won't be the easiest. It's nott a nice
flat surface. It's all fillet sanding and the fillets aren't the
smoothest..

justwaitaf...@gmail.com

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Jun 30, 2007, 12:29:01 PM6/30/07
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One thing I have found you can do is scrape nearly cured epoxy with a
dutch scraper, or even a wood rasp if you need to take down more
material. Of course, if you are painting opaque, you can use a fairing
compound to fill in areas which makes for easier sanding. Good luck,
keep the elbow brace handy...

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