On Tue, 18 Jan 2005 19:30:30 +0000, Grunff wrote:

I've heard this said quite a few times, but I'm really not sure. Think
about how it's formed - lots of bubbles of propellant expanding away in
a PU matrix. I'd say it is largely closed cell, with only a few through
paths. Its moisture absorbance is quite low.

It's effectively open cell, just slow. It doesn't matter if it's a
"mostly closed" cell foam, if you need it really sealed.

If you use the two-part foams, not the squirty can stuff, there are
grades of those that are real closed-cell foams.
--
Smert' spamionam