I. Advantages of Molecular Structure
Phenyl silicone rubber significantly improves its high-temperature stability by introducing phenyl functional groups (phenyl-to-silicon atom ratio of 5-30%) into the polysiloxane main chain. This structural design has the following key advantages:

Thermal stability of the phenyl group: The thermal stability of the benzene ring structure is far higher than that of the methyl group, effectively preventing the oxidative decomposition of side chain groups at high temperatures. The introduction of phenyl groups allows the material to maintain structural integrity even at 300°C, while general silicone rubber (methyl silicone rubber) begins to degrade significantly above 200°C.

Disruption of molecular regularity: The introduction of phenyl groups disrupts the regularity of the dimethylsiloxane structure, lowering the crystallization temperature of the polymer and making the material less prone to crystallization hardening at high temperatures, thus maintaining better elasticity.

Steric hindrance effect: The larger steric hindrance of the phenyl group effectively hinders the thermal motion of the molecular chains, reducing molecular chain slippage and breakage at high temperatures. This is a key factor in the stability of phenyl silicone rubber under high-temperature compression.

II. Comparison of Thermal Stability
Performance Indicator | Phenyl Silicone Rubber | General Silicone Rubber (Methyl Silicone Rubber)
Operating Temperature Range | -100℃ to 300℃ | -55℃ to 200℃
Elasticity Retention Time at 300℃ | Hundreds of hours | Several hours
High-Temperature Compression Set | <15% (250℃, 24h) | >30% (200℃, 24h)
Thermal Oxidation Stability | Excellent (phenyl group is oxidation resistant) | General (methyl group is easily oxidized)
The data shows that the performance degradation of phenyl silicone rubber at high temperatures is significantly slower than that of general silicone rubber. For example, low-phenyl silicone rubber vulcanizate can still maintain elasticity after dozens of hours of hot air aging at 350°C, while methyl silicone rubber will undergo significant hardening after long-term use at 200°C.

III. High-Temperature Compression Performance Mechanism
The main reasons for the excellent stability of phenyl silicone rubber in high-temperature compression applications include:

Low compression set: Phenyl silicone rubber has moderate molecular chain rigidity, allowing it to better resist plastic deformation under high-temperature compression. Experimental data shows that its compression set at 250℃ is more than 50% lower than that of general-purpose silicone rubber.

Creep resistance: The steric hindrance effect of the phenyl group enhances the intermolecular forces between molecular chains, making the material less prone to creep under continuous pressure, which is crucial for applications such as seals.

Thermomechanical stability: The glass transition temperature (Tg) of phenyl silicone rubber is lower than that of general-purpose silicone rubber (-140℃ vs -70℃), meaning that its molecular chain activity is more controllable at high temperatures and less prone to excessive relaxation.

Self-healing ability: Phenyl silicone rubber can better recover its original shape after high-temperature compression, due to the optimization of the molecular chain entanglement network structure by the introduction of phenyl groups.

IV. Application Examples and Performance Verification
Aerospace seals: In rocket engine sealing applications, phenyl silicone rubber products have a working life 3-5 times longer than general-purpose silicone rubber under high temperature (300℃) and high pressure (>10MPa) environments.

Automotive engine components: O-rings made of phenyl silicone rubber have a compression set of only 8% after long-term use in 200℃ engine oil, while methyl silicone rubber products have a deformation rate of 25% under the same conditions.

Electronic component packaging: High-temperature (250℃) aging tests show that the mechanical property retention rate of phenyl silicone rubber packaging materials is more than 40% higher than that of general-purpose silicone rubber.

V. Conclusion
The stability advantages of phenyl silicone rubber in high-temperature compression applications mainly stem from its unique molecular structure design: the phenyl functional group not only provides excellent thermal oxidative stability but also enhances intermolecular interactions through steric hindrance effects, enabling the material to better maintain structural integrity and elastic recovery capabilities under high temperature and pressure. These characteristics make phenyl silicone rubber an ideal choice for extreme high-temperature compression environments, especially in fields such as aerospace, automotive, and electronics, where material performance requirements are demanding.