Polyethylene foam for roadbed?

Polyethylene foam for roadbed?

Postby Arseny » Fri May 24, 2013 4:24 pm

Did anybody try to use polyethylene foam for roadbed, instead of cork roadbed?
I have some amount of this material; maybe it can work for roadbed?..
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Re: Polyethylene foam for roadbed?

Postby railtwister » Sat May 25, 2013 6:49 am

Hi Arseny,

Polyethylene is all but impossible to glue, which is why it is a material that is commonly used to make glue caps and containers out of. I don't know how you would bond it to the sub-roadbed, or bond the ballast to it. Track could be tacked down with nails going through the roadbed, I suppose, but what would work for attaching the ballast without peeling up or flaking off over time?

Bill in Ftl
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Re: Polyethylene foam for roadbed?

Postby WillYart » Sat May 25, 2013 8:32 pm

Some people are using that for roadbed, just a few mm thick; it's supposed to have good sound deadening qualities. I'm interested in trying it myself, but probably not on my current layout. A US manufacturer of this stuff (Depron) suggests using "UHU por", a German glue distributed internationally. It really works. One person online suggested letting the glue partly cure before introducing the polyethylene because it can melt the foam a little.

Google depron roadbed to see examples and photos.
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Re: Polyethylene foam for roadbed?

Postby railtwister » Sun May 26, 2013 12:06 pm

There are many types of foams made from different types of plastic; polystyrene, polyurethane, polyethylene, polyvinyl chloride, ABS, etc. All have different qualities, such as sensitivity to glues and solvents.

Depron foam is not polyethylene, according to the web it is polystyrene (see: <http://www.depronfoam.co.uk/html/what_is_depron.html>, which can be glued with some adhesives and foam-safe ACC, but also is very solvent sensitive, much more so than polyethylene. Polyethylene is very resistant to bonding with most types of solvent based glue, (including epoxies and ACC). Some adhesives such as silicone or acrylic caulk, may sort of work initially, but can usually be peeled off with very little effort.

Again, when using polyethylene foam for roadbed, it could be held in place by spiking through it into the sub-roadbed, but this would defeat sound-deadening, since the track nails or spikes would transmit the sound vibrations directly to the bench work.

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Re: Polyethylene foam for roadbed?

Postby WillYart » Mon May 27, 2013 1:19 am

I stand corrected: Depron = polystyrene. Thanks.
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Re: Polyethylene foam for roadbed?

Postby Arseny » Mon May 27, 2013 2:07 am

I'd talked about polyethylene foam. It is laminate floor underlayment, 2-3 mm thick, produced in Russia, it is named "Isolon" ("Изолон").

...Ok, I'll buy some cork laminate underlayment. 8-)
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Re: Polyethylene foam for roadbed?

Postby railtwister » Mon May 27, 2013 10:45 am

Arseny,

Why not try some of the foam you have on a small project, say a diorama, just to see how it works out? You could report back to the group about your findings.

There was an article in one of the major magazines (MR I think) a while back, about how someone had used carpeting underlayment for roadbed. The article even showed how he built a fixture to cut the material into strips with beveled edges. I'm not sure if this material is similar to what you have or not, I thought the underlayment in the article was more like a rubber product, and it was multi-colored. Most of the polyethylene foam I have seen here has been used for protective packing material, it is translucent white, soft, pliable, and feels kind of slippery to the fingers. It is great for protecting products in packaging, but resistant to all common adhesives that I have tried. I've also heard it called ethyfoam (spelling?).

Do they have anything like Homasote in your country? It is an insulating material made from paper pulp (recycled newspapers, I think), and is pressed into sheets about 12mm thick by 4'x8', sized to match plywood. It is sort of like a material known as Cellotex, but Homasote is only paper fibers, while Cellotex is softer and has tiny wood splinters in it. Homasote more tightly compressed, and holds track spikes well, while Cellotex does not. Homasote makes excellent roadbed and absorbs sound well, but needs a sub-roadbed to prevent sagging between supports. It is great for a permanent layout, but is very heavy, so it's not well suited for modules that need to be picked up and moved (unless you have a good Chiropractor).

Let know about your discoveries.

Bill in FtL
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