Foam question

[wes_mcgee]

While this is not directly a boat building project, I thought I might find some foam expertise around here.

I am looking for a high density foam, somthing in the range of polyurethane and renshape(I know, that is a broad range).

The key is I need it to be dissolvable. That eliminates all the polyurethanes(correct?). The only polystyrene I have experience with is common blue eps home insulation. It dissolves great, but is not nearly dense enough.

Are other polystyrene densities commonly available?

Any other dissolvable foams out there?

Thanks for the help,
Wes

[cyclops]

Spray in foam insulators can spray pure liquids if you have the money. How many PSI to compress 1" of the foam? We need some hard numbers.

[marshmat]

How dense are you looking for?

Polystyrene is usually made to be fairly low-density since it's used as insulation or flotation. Since I take it you want to dissolve it with something like acetone, and not styrene or perchloric acid, polystyrene would seem a good choice but the higher densities, while they do exist, are hard to find. What exactly do you need it for?

[wes_mcgee]

three part mold cores/dissolvable cores....


was hoping for something in the 10 to 20 lb/ft3 range....

[yokebutt]

Wes,

Have you considered using silicone rubber molds?

Yoke.

[wes_mcgee]

Maybe, we use a variety of urethane rubber A/B products...

usually for the outer surface on a mold with poor draft angles, or one that needs to be reuseable.

For the third part of the mold, I was looking for a simple material that could machine well, and be melted out(but not with high temperatures), to create one piece shells, without complicated internal collapsible structures. SOme hard machinable wax may be the answer, though I am not sure how expensive that can get. Seems messier than a foam too.

I don't know much about the pros cons of silicone?

[wet feet]

There are products other than foams that can be dissolved after use,somewhat in the manner of wax in investment casting.I have done a few tests with two plaster type materials that are water soluble.I have now left the company I worked for when doing this work and have to rely on memory for the following information.They go by the names of aquacore and aquapour and originate in the US,you may be able to find more information.

[cristofa]

Other questions come to mind ... what is the size and complexity of the inside shape? And how many are to be made? And how important is the internal surface finish? And how big is the access to the inside in relation to the whole?

atb ... Christopher

[yokebutt]

Well then, if we combine a few ideas in this thread, how about first making a male plug, then a female silicone mold off of that, then cast dissolvable (and expendable) plaster blanks in the silicone mold?

Yoke.