re Silicon sealer breakdown.
I am a habitual beach comber, I often find whats left of a silicon sealer cartridge after its been burned in a bonfire, the plastic cartridge disappears and the silicon is left as a perfect mold , with all its rubberiness still intact.
"Silicone rubbers are often one- or two-part polymers, and may contain fillers to improve properties or reduce cost. Silicone rubber is generally non-reactive, stable, and resistant to extreme environments and temperatures from -55 Â°C to+300 Â°C while still maintaining its useful properties."
In service as an exhaust port sealer it must be close to its upper temp limit , but Ive not had it fail , yet!.