Quote:
Originally Posted by J[_6_]
I was looking at the stuff specifically for "larger cavities" but even that claims that it will not cure properly if there is no air. I'm not too worried about the easily accessible spaces - it's more the tunnels that I can't see where they go. I can't see how I could possibly layer the foam in the tunnels - especially when they start out going in and up. But maybe it's not too critical if the foam in the tunnels doesn't cure properly as long as it cures at the exit points.
-J
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Those instructions need some explanation.
Great Stuff, and so far as I know all the other expanding "Polyurethane" foam caulks are in fact polyisocyanates. They react with the MOISTURE in the air to form a polyurea foam and CO2 gas. It's actually the CO2 gas that gets produced when the isocyanates react with moisture in the air that acts as a blowing gas to cause the foam to inflate and expand. So, if the foam is inflating / expanding, that means the chemical reaction with the moisture in the air has already occured. After that there's a drying process that happens as solvents evaporate from the foam, but so far as I now, those solvents can evaporate right through the foam just like solvent can evaporate right through a "wet" oil based paint film.
So, it's not really air that's the critical factor, it's the amount of humidity in the air. The foam won't work if there's no moisture in the air, and this can happen on really really cold days in winter (if you live where I live) when it's 40 degrees below Zero or colder and there is barely any humidity in the air. I guess what the instructions are getting at is that if access to a cavity is restricted, there might not be enough humidity in the cavity for all of the isocyanates injected to react.
If it wuz me, I would use any expanding foam, and I would go to any place that sells small tubing (like hydroponic garden shops) and get some flexible tubing that will fit over the nozzle of the can snugly. Cut that tubing to 18 inch lengths or so and insert the tubes into the tunnels. Inject the foam while pulling the tube outward to fill up that 18 inch of tunnel.
Both cured and uncured polyurethane foam can be cleaned off of most clothing with acetone. Acetone is commonly found in nail polish remover, but you can buy acetone by the quart or gallon at any paint or hardware store or home center. The only clothing that acetone will dissolve are acrylics which are typically found in KNIT touques, scarves and mittens. Any fabric whose label that says the garment is made of "Acrylic" will dissolve in acetone.
Keep plenty of newspaper around to throw the used pieces of tubing onto. Clean the nozzle with acetone if necessary after every injection of foam. Using an eye dropper helps to get the acetone into the nozzle and the outlet of the can. You can buy eye droppers at any pharmacy.