Phenyl raw rubber, as a key raw material for preparing phenyl silicone rubber, exhibits superior performance advantages in the field of heat-resistant aging sealing materials. By controlling the phenyl content, the heat resistance, aging resistance, and sealing performance of the material can be precisely optimized.

1. Relationship between Phenyl Content and Heat Resistance
The phenyl content directly affects the heat resistance grade of the material:
Low-phenyl silicone rubber (5-10% phenyl content): Has the best low-temperature resistance, with a curing temperature as low as -115℃, and maintains good elasticity at -100℃, but its high-temperature resistance is relatively limited.

Medium-phenyl silicone rubber (15-25% phenyl content): While maintaining good low-temperature performance, it significantly improves ablation resistance, possesses self-extinguishing properties, and has a temperature resistance range of -70℃ to 350℃.

High-phenyl silicone rubber (phenyl content above 30%): Exhibits superior high-temperature resistance, with a long-term service temperature up to 350℃ and short-term tolerance to 400℃. It also possesses excellent radiation resistance (withstanding 2.58 × 10⁴ C/kg γ-rays).

2. Optimization Mechanism of Heat Aging Resistance
The effect of the phenyl structure on thermal stability: The introduction of phenyl enhances the rigidity of the molecular chain, increasing the glass transition temperature of the material, allowing the silicone rubber to maintain structural stability at high temperatures.

The adsorption effect of phenyl on free radicals: Under high-temperature conditions, phenyl can effectively adsorb free radicals generated by heat, slowing down the oxidative degradation process and significantly improving the thermal stability of the material.

Optimization of crosslinking density: Appropriately increasing the phenyl content can increase the crosslinking density of the vulcanizate, enhancing the retention of mechanical properties at high temperatures.

3. Key Applications of Heat-Resistant Aging Sealing Materials
Sealing Performance in Extreme Temperature Environments:

Aerospace: Phenyl silicone rubber seals perform excellently in satellite orbit operations, maintaining good elasticity while withstanding direct sunlight (120°C) and Earth's shadow (-100°C), ensuring the safety of the "protective door" for precision instruments.

Nuclear Power: High-phenyl silicone rubber, as the matrix for neutron shielding materials, can operate stably for extended periods in environments above 300°C with a total weight loss of less than 10%, providing reliable sealing for nuclear reactors.

Automotive Industry: Used in engine seals and exhaust systems, it can withstand high temperatures and chemical corrosion, effectively preventing oil and gas leaks and ensuring normal engine operation.

4. Experimental Verification of Heat Aging Resistance
Heat Aging Performance Test Results: Under hot air aging conditions of 300-350°C, the crosslinking density of phenyl silicone rubber decreases with increasing temperature, and its physical and mechanical properties gradually decline. However, the performance degradation is more slow for products with high phenyl content.

Long-term thermal stability: After 500 hours of heat aging at 300℃, the total weight loss of the high-phenyl silicone rubber composite is less than 10%, demonstrating excellent long-term thermal stability.

Damping performance retention: As the heat aging temperature increases, the dielectric loss factor of phenyl silicone rubber gradually increases in low- and medium-frequency environments, but the damping performance of high-phenyl content products remains better.

5. Optimization strategies in practical applications
Practical methods to improve heat aging resistance:
* Filler modification: Adding inorganic fillers such as silica, iron oxide, and chopped carbon fibers can significantly improve the thermal stability of phenyl silicone rubber, with iron oxide showing the most significant effect on improving residual carbon content.
* Phenyl content control: Selecting appropriate phenyl content for different application environments, such as prioritizing medium- to high-phenyl content (15-30%) for high-temperature sealing, while balancing heat resistance and low-temperature performance.
* Composite vulcanization system: Using composite vulcanization systems such as HVA-2, TAIC, TMTD, and DCP can improve the thermal stability and mechanical properties of the blend.

By controlling the phenyl content and using scientifically designed formulations, phenyl raw rubber can be used to prepare heat-resistant sealing materials that can withstand various extreme temperature environments. Products with high phenyl content (20-30%) exhibit the most outstanding performance in heat aging resistance, making them particularly suitable for fields such as aerospace and nuclear power where high-temperature resistance of sealing materials is critical. Their long-term operating temperature can reach 350℃, and their short-term temperature resistance can reach 400℃, while maintaining good sealing reliability and mechanical properties.