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#1
posted to rec.boats.building
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Polyurethane paint
Someone told me it won't adhere to to epoxy. True or false?
Thanks Gordon |
#2
posted to rec.boats.building
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Polyurethane paint
Gordon wrote:
Someone told me it won't adhere to to epoxy. True or false? You shoot high build primer first, then L/P. Lew |
#3
posted to rec.boats.building
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Polyurethane paint
Flase.
Both one and two part polyurethanes are great finishes over epoxy substrates *provided* there is no remaining 'amine blush.' Manufacturers of PU (like Interlux) have all developed a 'tie coat' or 'primer' to isolate the epoxy sustrate from the overcoating paint. Here's what Interlux says: "Be sure to use Epoxy Barrier-Kote 404/414 over clear epoxy to prevent blush from affecting drying and adhesion of Brightside". MW |
#4
posted to rec.boats.building
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Polyurethane paint
I have another question about polyurethane paint. After priming the
epoxy and using a poly paint would it be lighter in weight than gel coat finish and more fade resistant. The weight issue is important because I'm using it on a canoe. wrote: Flase. Both one and two part polyurethanes are great finishes over epoxy substrates *provided* there is no remaining 'amine blush.' Manufacturers of PU (like Interlux) have all developed a 'tie coat' or 'primer' to isolate the epoxy sustrate from the overcoating paint. Here's what Interlux says: "Be sure to use Epoxy Barrier-Kote 404/414 over clear epoxy to prevent blush from affecting drying and adhesion of Brightside". MW |
#5
posted to rec.boats.building
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Polyurethane paint
I think we're talking ablout two different construction methods...
"Gelcoat" generally implies female mold, fiberglass laminate construction with polyester resins, where the colored gelcoat is applied against a release agent, (preventing the gelcoat from sticking to the mold) followed by a few to many-many layers of fiberglass of various weaves & thickness. Here, the 'color' is the *first* item to be applied (against the female mold). "Paint" is generally used in male mold construction, mostly used in "one-off" boat building. (Paint is also used over "old gelcoat" after it has faded after years of sun/abuse/neglect). In M-M construction, various materials (cold-molded wood, sheet "foam", fiberglass planking) are laid over a male mold with the hull thickness then laminated up (often using epoxy resins) with either additional wood veniers, woven or knitted fiberglass, kevlar, carbon fiber or what-have-you. Here, the paint (color) is applied *last*, against a primer that acts as an adhesion base for the paint as well as a barrier against any epoxy 'blush'. As to the weight: One applies Polyurethane paint in multiple (like 3) *very* thin coats. I'd guess you could do a canoe with about a quart of paint / solvent / reducer which might weigh (guessing) about 2 lbs (total). MW Los Angeles |
#6
posted to rec.boats.building
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Polyurethane paint
If Gelcoat is used in a female mold then no filler / fairing should be
required. If paint is used over glass then usually some amount of filler and fairing would be required. The weight of filler under the pain should easily exceed the total weight of gelcoat. Having said that I wouldn't think that the weight difference between gelcoat and painting would be significant enough to worry about and it would be pretty difficult to accurately calculate. If painting so much would depend on technique. wrote in message ups.com... I think we're talking ablout two different construction methods... "Gelcoat" generally implies female mold, fiberglass laminate construction with polyester resins, where the colored gelcoat is applied against a release agent, (preventing the gelcoat from sticking to the mold) followed by a few to many-many layers of fiberglass of various weaves & thickness. Here, the 'color' is the *first* item to be applied (against the female mold). "Paint" is generally used in male mold construction, mostly used in "one-off" boat building. (Paint is also used over "old gelcoat" after it has faded after years of sun/abuse/neglect). In M-M construction, various materials (cold-molded wood, sheet "foam", fiberglass planking) are laid over a male mold with the hull thickness then laminated up (often using epoxy resins) with either additional wood veniers, woven or knitted fiberglass, kevlar, carbon fiber or what-have-you. Here, the paint (color) is applied *last*, against a primer that acts as an adhesion base for the paint as well as a barrier against any epoxy 'blush'. As to the weight: One applies Polyurethane paint in multiple (like 3) *very* thin coats. I'd guess you could do a canoe with about a quart of paint / solvent / reducer which might weigh (guessing) about 2 lbs (total). MW Los Angeles |
#7
posted to rec.boats.building
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Polyurethane paint
Douglas wrote:
I have another question about polyurethane paint. After priming the epoxy and using a poly paint would it be lighter in weight than gel coat finish and more fade resistant. The weight issue is important because I'm using it on a canoe. wrote: Flase. Both one and two part polyurethanes are great finishes over epoxy substrates *provided* there is no remaining 'amine blush.' Manufacturers of PU (like Interlux) have all developed a 'tie coat' or 'primer' to isolate the epoxy sustrate from the overcoating paint. Here's what Interlux says: "Be sure to use Epoxy Barrier-Kote 404/414 over clear epoxy to prevent blush from affecting drying and adhesion of Brightside". MW Gelcoat is heavier guaranteed. It's a thick coloured resin layer vs. thin polyurethane paint. Evan Gatehouse |
#8
posted to rec.boats.building
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Polyurethane paint
Gordon wrote:
Someone told me it won't adhere to to epoxy. True or false? Thanks Gordon epoxy is the common primer under two part poly (LPU) coatings. paul oman progressive epoxy polymers. |
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