----- Original Message -----
Sent: Thursday, June 21, 2007 12:33
PM
Subject: [FlyRotary] Re: Proseal was Re:
PP construction methods
Marv,Tracy,et al,
Any numbers on the degrees of heat
that Polysulfide or the
newer Polyurethane can handle without degrading??
--
Kelly Troyer
"Dyke Delta"_13B
ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold
--------------
Original message from marv@lancair.net: --------------
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 appl ications.
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
"""