What is max service temperature of GE Silicone II sealant caulking?

 I'm looking for some high-temperature sealant / caulking to use on my
furnace (instead of using duct tape or aluminized tape).  This is for
seams in the usual places where air tends to leak out of the duct work
and where the furnace connects to the ducts.  This is not for the flue.

I expect the max temperature to be around 200C, and mostly between 50C
and 100C.

I was searching the net for specs on GE's various sealant products, but
can't find very much about max service temperature.

Here's an example of what I can buy at home depot (Canada):

http://tinyurl.com/2baqhwj

This might be different than what's available in the USA (perhaps only
the label is different, or maybe the formulation is different - I don't
know).

Home Depot in Canada doesn't sell a caulking / sealant product that's
specifically labeled as "high temperature", or furnace, stove or HVAC
duct use.

What I did find at HD is 3 different 3M caulk products, labelled
variously as "Fire Barrier" Sealant IC 15WB (and two others that had a
similar application).  These are designed or marketed as sealants that
are applied in drywall seams and around pipes and wires as they pass
through walls (drywall, brick, cement, etc) and I guess they're meant to
contain fire or smoke for maybe an hour or two.  I did find on-line
cheps for one of them - and it had a paltry max service temperature of
48C.

I imagine that a job-shop HVAC supplier would probably have high-temp
caulking, but I'm just curious if something like the GE Silicone II
would do just as well (200C really isin't high-temp).

  On Sat, 06 Nov 2010 18:11:10 -0400, Sum Guy wrote:


Well considering your hight temp cut off is around 90c I would work with
that figure. Any Silicone will easily handle furnace ductwork from the
plenum outwards.

 "A. Baum" wrote:


There are seams that run close to where the flue exits the furnace that
will quite likely exceed 100C for extended periods.

 Sum Guy wrote:

I have seen 400-500 degree celcius mentioned for
silicon and you can sort of verify that with a
soldering iron.
That should not make it melt down.
At higher temps it turns into a white powder, without
melting, and starts smouldering..

 On 11/6/2010 6:11 PM, Sum Guy wrote:

I used a clear silicone, think it was the type I, to seal around glass
doors on fire place.  Holds up well.