What Commercially High Temp Gasket Materials Are Available

It depends on various other factors such as Pressure, and on the Media.

In general, the high temperature limit for most commercially available "Rubber" products is below 500°F (204 - 260°C). Within "Rubber" materials, Phelps 7175 - Silicone inherently has the best temperature stability of these. The standard operating temperature for silicone ranges from 400 - 500°F (204 - 260°C) with intermittent temperature up to 600°F (333°C).

Other materials such as fluorocarbon, EPDM and fluorosilicone have good to excellent heat resistance. This means the gasket material maintains its mechanical properties and will continue to perform as designed without reversion.

Phelps Green sheets and Frenzelit Novatec and Novaphit are great for sustained 300°F temperatures in steam applications used in Ship Engines, and Heavy  Duty Diesel Engines etc.

Phelps Flexible Graphite Sheets are idea for even higher (500°F or higher) temperature Petrochemical applications.