Silicone gaskets: what 200 C really means
Standard silicone sheet is a -60 to 200 C material. Above that, the elastomer degrades; modified grades extend the range but not indefinitely.
High-temperature gaskets divide into metallic, non-metallic, organic and inorganic groups. The selection logic starts from the duty: working temperature, medium, and the sealing precision the joint needs.
Silicone gasket sheet is a non-metallic elastomeric product covered by GB/T 38571, used for ambient and moderate temperature sealing. Compared with metal gaskets it has lower conductivity and slower heat transfer, good slip resistance and enough elasticity to fill surface irregularities in a static joint.
The numbers to hold on to
Standard silicone sheet is rated from -60 C to 200 C continuously. At 200 C it is at its limit; it does not hold sealing performance or material stability at 300 C and above. Modified and composite grades raise the ceiling for specific duties, and the data sheet for the grade in question is the only figure worth quoting.
Reference note. Figures and standard references are indicative and do not replace the project specification, the current edition of the standard, or product test reports for the specific supply.