What are the characteristics of the heat resistance change of platinum catalytic system silicone at different curing agent addition ratios?

What are the characteristics of the heat resistance change of addition-type silicone (platinum catalytic system) at different curing agent addition ratios?
The heat resistance change of addition-type silicone (platinum catalytic system) at different curing agent addition ratios presents the following characteristics:
When the curing agent ratio is too low:
Incomplete cross-linking reaction: The silane addition reaction is insufficient, and a large number of uncross-linked linear molecular chains remain. These uncross-linked parts are prone to thermal oxidation chain breakage at high temperatures, resulting in a sharp drop in the heat resistance of silicone. For example, when the curing agent (component B) is too little, such as when the ratio of components A and B is much greater than the standard 10:1, the long-term temperature resistance may drop from the standard 180-220℃ to 130-150℃.
Rapid high-temperature performance deterioration: Even in a short-term high-temperature environment, there will be obvious performance changes due to the instability of the molecular chain. For example, after being placed at 180℃ for 100 hours, hardening and embrittlement may occur, and in the long-term use process, slow thermal oxidation aging will accelerate performance degradation.
Too high a curing agent ratio:
Initiates over-crosslinking or reverse reaction: Excessive hydrogen-containing silicone oil (curing agent component) forms too many active centers with platinum catalyst, which may cause "over-crosslinking" at high temperature, making the molecular chain over-crosslinked and becoming too rigid and less flexible, and prone to cracking due to stress concentration at high temperature. At the same time, it may also trigger reverse reactions, such as the breaking of silicon-hydrogen bonds, resulting in a decrease in the performance of silicone in high temperature areas. For example, when there is too much component B and the ratio of components A and B reaches 5:1, in a high temperature environment above 200°C, the mass loss may be aggravated due to excessive molecular chain breaking, and the weight loss rate is higher than the standard ratio.
Increased risk of catalyst poisoning: Excessive platinum catalyst may absorb impurities in the air, such as sulfides, to form catalytic poisons, indirectly reducing the high-temperature stability of silicone and affecting its heat resistance.
Moderate curing agent ratio: At this time, the silicon-hydrogen addition reaction is sufficient and moderate, the crosslinking density is high and uniform, and a stable network structure is formed between molecular chains. This makes it difficult for the molecular chains of silicone to move at high temperatures, significantly increases the heat deformation temperature and Vicat softening point, has good heat resistance, and can maintain good performance in the long-term temperature range of 180-220℃ and short-term temperature range of 250-300℃. There is basically no obvious change after high-temperature aging, and the elasticity retention rate is high.