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Old 26-04-2021, 00:08   #1
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Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

Hey, thinking out of the box here. I am aware that we tread unproven ground.
Still, maybe someone has given it a try.

We have a XPS foam shape which we would like to laminate over with epoxy & biaxial glass.
As XPS is closed cell I know that laminates glued to it can peel off, especially if its a hand lay up without vaccuum.
Now here comes a bit of an unconventional idea. Maybe someone has tried it?

How about using 5200 or something similar to stick the first (thick) layer of dry fiberglass (without epoxya) onto the 36grit sanded XPS foam and then laminating onto that "dry" glass layer from the outside.

The total glass layer is 5-8mm thick and the foam is primarely a former for a fairing. The foam is completly encapsulated and can not go anywhere.
Could that work better than laminating straight onto the XPS foam?
I KNOW that is unvconventional thinking, but I do wonder if it COULD work.

Especially knowing that 5200 sticks like hell to all sorts of materials. Thoughts ideas?

Thanks!

Btw. 5200 is a one pot polyurethane, what separates it from other polyurethane glues?
Are there similar formulations used on an industrial scales which do not carry a premium "marine" price tag? Brand names? Recommendations?
As the stuff is not exposed to sunlight at all we could perhaps use a cheaper alternative?
How about this: https://samaro.fr/pdf/FT/HBFULLER_FT...5-45___FR_.pdf
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Old 26-04-2021, 00:34   #2
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

I guess the only way of knowing if it will work is to do a test piece and see

In the UK we have a product called CT1. This sticks like the proverbial to anything!
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Old 26-04-2021, 03:17   #3
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

I wouldn't stick dry glass to 5200 and then hope that epoxy would soak it fully--the glass needs to be clean and dry so that capillary action can help the resin impregnate all the way.
Better to rough up the surface of the XPS with sandpaper, and, if you're really worried about an encapsulated piece of foam moving (where would it go?) drill a bunch of small holes in it for a hotcoat of thickened resin to flow into and grab on.
I make shapes with XPS all the time, and never worry about the epoxy not sticking.
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Old 26-04-2021, 04:03   #4
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

There is no reason to do this as epoxy sticks just fine to xps. It’s the xps itself that will fail in extreme conditions, pulling foam away with the epoxy as a force is applied along the normal vector.

Xps is weak stuff in comparison to structural foam, but for something not undergoing a lot of repeated physical stress, it’s just fine. I’m actually in the process of using some myself right now to make a Fairing/cowling to keep rain off some equipment. Since I can’t use epoxy, I used a special polyester. Xps is good stuff for interior cabinetry, fairings and partitions. Things that aren’t structural and are not under significant, repeated loading and unloading.

So I think you’re getting mixed up here as epoxy is one of the best things you can use to bond to xps.
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Old 26-04-2021, 09:49   #5
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

What Benz and Chotu said. I've used a thin kerf saw blade set at 2mm and 45* angle to cut inverted "V" grooves in XPS then put a hot layer of epoxy with some filler followed by biaxial cloth and resin. No need to use a urethane.
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Old 26-04-2021, 12:42   #6
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

Quote:
Originally Posted by Chotu View Post
There is no reason to do this as epoxy sticks just fine to xps. It’s the xps itself that will fail in extreme conditions, pulling foam away with the epoxy as a force is applied along the normal vector.

Xps is weak stuff in comparison to structural foam, but for something not undergoing a lot of repeated physical stress, it’s just fine. I’m actually in the process of using some myself right now to make a Fairing/cowling to keep rain off some equipment. Since I can’t use epoxy, I used a special polyester. Xps is good stuff for interior cabinetry, fairings and partitions. Things that aren’t structural and are not under significant, repeated loading and unloading.

So I think you’re getting mixed up here as epoxy is one of the best things you can use to bond to xps.
I second this - I have had very good success bonding glass to XPS with epoxy. Polyester melts it.
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Old 26-04-2021, 13:22   #7
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

Epoxy is far superior to 5200 and cheaper as well. Alos the glass can't absorb epoxy if it's already saturated with 5200. This means it won't have any compression strength, only tensile. But given that 5-8 mils of glass is a lot of glass (why) the foam's bond isn't needed and wouldn't hold up anyway as it would just break under a load. You didn't mention what this is for, or what loads it needs to take.
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Old 26-04-2021, 13:42   #8
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

Some thoughts after reading the thread so far:
-Low VOC polyester (Duratec Styro-Safe) has worked well for me in the past on EPS foam, never tried on XPS. I have seen some melting if this resin is allowed to pool against EPS but does fine in a normal lamination.
-Some people use coarse sandpaper or a board with nails to poke many small holes in XPS to give the surface 'tooth'. Since I still have lots of EPS I have yet to try this on XPS.
-The troubles seem to happen on thinner laminations (surfboards, etc) that are exposed to heat/sunlight so as to expand pockets of air and promote delamination.
-Epoxies are a stoichiometric reaction, simply put so many parts A are consumed to a part B. With normal components there is no such thing as a 'hot' mix. Anything left over/extra part A or part B affects the overall strength of the mix as a plasticizer or contaminate.
-Most people will choose the correct hardener for the desired working time and air temperature rather than add a true chemical accelerant.
-Mixing epoxy in a bucket-shaped container and not spreading it out right away can/will promote a runaway exothermic reaction.
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Old 26-04-2021, 22:47   #9
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Re: Crazy idea? Keying XPS foam with laminate with 5200 or similar? Someone tried it?

Quote:
Originally Posted by Franziska View Post
Hey, thinking out of the box here. I am aware that we tread unproven ground.
Still, maybe someone has given it a try.

We have a XPS foam shape which we would like to laminate over with epoxy & biaxial glass.
As XPS is closed cell I know that laminates glued to it can peel off, especially if its a hand lay up without vaccuum.
Now here comes a bit of an unconventional idea. Maybe someone has tried it?

How about using 5200 or something similar to stick the first (thick) layer of dry fiberglass (without epoxya) onto the 36grit sanded XPS foam and then laminating onto that "dry" glass layer from the outside.

The total glass layer is 5-8mm thick and the foam is primarely a former for a fairing. The foam is completly encapsulated and can not go anywhere.
Could that work better than laminating straight onto the XPS foam?
I KNOW that is unvconventional thinking, but I do wonder if it COULD work.

Especially knowing that 5200 sticks like hell to all sorts of materials. Thoughts ideas?

Thanks!

Btw. 5200 is a one pot polyurethane, what separates it from other polyurethane glues?
Are there similar formulations used on an industrial scales which do not carry a premium "marine" price tag? Brand names? Recommendations?
As the stuff is not exposed to sunlight at all we could perhaps use a cheaper alternative?
How about this: https://samaro.fr/pdf/FT/HBFULLER_FT...5-45___FR_.pdf
Baby carrot!! Or more precisely what gets ejected from said baby after feeding mashed carrots! Sticks to everything I am assured!
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