Expanding PU foams vs Epoxy foam properties/handling

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#1

I’m wondering if I can use a cured foam as a male tool surface onto which I can laminate and then envelope vac bag.

My ideal material of choice would be

  1. moderate -high density for compressive strength under vac bag vacuum conditions,
  2. easily removed by either dissolving (or the very least chipping and hacking away at it…:frowning: pita…)
  3. can withstand elevated cure temps up to 120C

PU vs Epoxy foam:

Anyone have practical experience with cutting either PU foam or Epoxy foam? Which is easier?

The higher densitiy versions of pourable expanding foam are said to be decent structural surfaces and also allow machining. So does that confer the same thing as compressive strength for example under vacuum?

I would need the foam to be dimensionally stable at eleveated temperatures.

Thanks.

Edit: anyone ever hear of this core material? IT seems its a soluble and reusable solid core material. http://www.nevadacomposites.com/properties.php

#2

I don’t know if PU foam would remain stable at those temperatures. It should remain quite stable under vacuum, but beware of corners, they will flatten out.
Epoxy foam could be stable, and is a lot stronger. It needs a postcure though.
both foams can’t be washed out with solvents.
One method in creating cheap moulds is to mill them from styrofoam, then envelope bag the thing in stretchlon or similar at low pressure, end then laminate over it, and apply a high pressure bag over that.

haven’t workeed with water soluble core material

#3

Thanks!
I figure the physical properties of the epoxy foam would be favorable compared to the PU… I will have to physically remove the epoxy core foam after layup. Any suggestions? I’m guessing drilling with a large bore drill bit and hacking it out, maybe using a reciprocating hand saw? any creative suggestions?

Is there anything that you can think of to place internally into the mold that would form something like a lattice around which the foam could be pourd in and cured. So once the cured foam is ready to be removed the lattice captured within the foam is easier to break up and then the chunks of foam are easier to remove? :confused: best imaginative half solution I could come up with lol…

#4

What about Aquacore? Or the do it yourself version from PVA and microballons. But make sure it is dryed complete before using it.

#5

I looked at aqua core, the page that lists the prices won’t open… anyways someone else chimed in in a separate thread about aquacore I started a while back and they said it was $$$.

I didnt realize that pva and microballoons would work. Any tips on how that’s done? I also thought about a core using sodium silicate and microballoons(used as a sand core binder and it’s supposed to be soluble by water if not exposed to high heat)

#6

That also works. Mix it so you can form it and then cure it. Or make a block (best will be layer by layer) and cure it. Sand also works but is quite heavy at the end.

#7

do you get in touch with nevadacomposites? any trial? i am also looking for such solution