I may be wrong but I think the name may be "Kool Seal". It dries but looks like its flexible,don't think it will ever come lose and blow off it might in pieces like paint. I would not think it would be all that heavy,but it might. It also helps keep the trailer cooler inside. It does do a good job of stopping small leaks,and will not run off like tar.
PS Make the top look like new again.