Polysulfide is an old standby in the insulating glass industry for sealing the edges of insulating glass units (think thermopane).  It sticks like grim death to most substrates (as long as they're clean and degreased) and it retains a good bit of its flexibility for a very long time.  Typical insulated glass units sealed with the stuff would carry a 20 year warranty against seal failure as long as the sealant was properly protected from the elements and especially the sunlight... it degrades rapidly with high exposure to UV.  The only thing I know of that's stickier are the more recent polyurethane sealants, but the industrial versions I'm familiar with are not readily available to the general public and are sold only in 50 gal drum quantities accompanied by a 5gal pail of catalyst.  Both products can put up with pretty high heat levels, so they are well suited to a wide range of applications.  A big difference between the two, although not germaine to this discussion, is that polysulfide does not provide a moisture vapor barrier, ie, it's permeable to water vapor, whereas polyurethane isn't.

  <Marv>


 "Ed Anderson" <eanderson@carolina.rr.com> wrote:
"""
That Polysulfide is remarkable stuff. When I started to put together the two
parts of an 2 1/4" instrument case, the 3/8" thick flange and the 2.25" tube,
I scratched my head over how to join the two. Set screws were simply too
labor intensive, crazy glue was too brittle - but, I had some "tank sealer"
left over (years on the shelf) which I mixed a small amount together, smeared
a thin amount on the inside of the flange and pushed the tube in.

Once it set I could not get the tube out of the flange without destroying the
aluminum tube. Really sticks and doesn't turn brittle.

Ed
"""