It seems I've been seeing a lot of uses for foam on this site, from a weapon to a spaceship defense mechanism. However, the details on what the foam is made of and how it works always seem lacking to me; thus, I worry that many of these foams are just science fiction.
My question is is there a foam that can be used to quickly construct airtight walls solid enough to keep humans out? I imagine using this foam on a spaceship to trap the enemy, or alternately to fix hull breaches. Perhaps there is a fast-acting variant that can be used as a grenade to immobilize enemies. As it is a foam, it could be carried around much more easily than other wall-building materials, thus I could outfit my space marines with a few cans apiece.
So, does this foaming material exist, or is there a theoritcal way to produce it? If so, how big would the initial substance be, and how long would it take to dry/harden?
The foam need not be activated by air; on the contrary, it would be great if it contains its own reactants, and can be activated in a vacuum.
It need not last; it should only be functional for a minimum of a couple hours. If it breaks down after that, that's fine.
I would like it to be as strong as possible. If it can get to concrete levels, that would be best, but as long as it's very difficult for a human to burrow through that'll work.