On 9/11/2011 4:27 AM, harry wrote:
On Sep 11, 2:50 am, Home wrote:
I'm trying to apply some expanding foam to the inside of a closed
garbage bag that's situated between two surfaces that are about an inch
apart. I want the foam to take the shape of the irregular surfaces as
it expands and hardens, but I don't want the foam to adhere or bond to
these surfaces so I've placed an ordinary plastic garbage bag between
them and that's where the foam is being injected.

I'm discovering that the small amount of foam that's leaking out of the
fill-holes is expanding and curing nicely, but the foam inside the bag
seems to be semi-solid goop. I'm leaving this over night to see if it's
any better tommorrow, but I'm thinking I'm going to need a different
sort of product other than "Big Stuff" aerosol can gap filler.

I know there's some foam packing material that is isin't particularly
messy and I think is applied inside a bag or membrane that conforms to
the shape of what-ever is being shipped. Is this stuff available?

Any other ideas?

The canned foam needs water to make it set. It gets this from the air.
So, in an enclosed space it won't go off unless you spray the surfaces
inside with water . Even then it isn't so good sometimes. It sticks
to damp surfaces even better than dry.
So you need to wet the inside of your bags. But even so, results are
variable.
If you spray the foam too thick/too big a blob, it won't go off,
remaining soft in the centre for a long time. The gas usually escapes
eventually leaving a big void inside.

The two part foam goes off regardless.

Decent article on chemistry:

http://en.wikipedia.org/wiki/Polyurethane

Bubbles in the foam are from carbon dioxide liberated when isocyanate
reacts with water. In a two parter water could be in the polyol and two
parter is needed by op.