Elmer's Ultrabond Polyurethane? Huh?

Looks like you may have happened onto either some sort of structural adhesive, or maybe a wood adhesive product. Being it's a polymer based adhesive you could probably use it on your models without major problems--if you want to wait several hours or so for it to cure. As I understand it, these adhesives are designed to produce strong bonds, while allowing a significant "open" period of time to allow for positioning, etc. Once cured (depending on working temperatures), the material is fairly hard, and can be formed by sanding, etc.
One down side, however: All poyurethanes are produced using chemicals called isocyanates. These materials are quite toxic in very small quantities, and can cause sensitization reactions in susceptible individuals. Repeated exposures may cause chemical asthma or chemical bronchitis. Isocyanates have also been shown to cause cancer in animals (no human data, yet).
I think I'd stick to plain old liquid cement (or whatever you're currently using) and maybe a small amount of CA on the side.

Hope this helps.
Gip Winecoff

Gip,

I have used this product on projects around the house and it is incredibly strong. The only downside besides the ones you mentioned is that this glue expands while curing and must be clamped. It also requires moisture to cure so you have to dampen the parts being glued.
I glued some 1" thick high-density foam to a piece of plywood and sat barbell weights on the board as it cured. Later that day I checked on it and the Elmer's Pro Bond glue had literally penetrated the entire 1" of foam and was oozing out of the pores in the foam on the surface. [:0]
I might add that the foam is now permanently bonded to the wood I glued it to.
The most popular brand of polyurethane glues is Gorilla Glue which is sold at many places and it is supposed to be the best.
Make sure you wear rubber gloves while using this stuff also as I have read that if it gets on your hands and dries you will not get it off with anything other than a file or sandpaper.
I would not recommend it for model building though as it takes 1-4 hours to set and 24 hours to fully cure. I think the glues like Tenax 7R and Cyanoacrylates, along with Epoxies are all that a modeler needs.

On another note have you seen these other glues they have come out with? One is called CoolChem Cyanopoxy and it is incredible.
It is expensive but I have seen it on an auto show on TV one time and the strength of this glue is incredible.

http://www.americansteel.net/coolchem/coolchem1.asp

Mike

Mike,
I just checked out the link you provided, and the cyanopoxy sounds pretty convincing. Not sure that it would benefit us in the modeling hobby very much, and the material seems to be pretty cost prohibitive at the moment. Wonder if you could pour the stuff into a mold, and then add the activator----instant casting! I'll bet the stuff can even be drilled, sanded, etc.--Might be good for scratchbuilding......(?)

Gip Winecoff

Maybe that would work Gip.

I have used a product on my boat hull called Marine-Tex and it can be drilled and tapped just like steel. It is some amazing stuff also.

Mike