Phenyl silicone rubber, thanks to its unique molecular structure design, achieves groundbreaking performance in extreme low-temperature environments, maintaining excellent elasticity and functional stability even below -196°C (liquid nitrogen temperature). It is widely used in aerospace, deep space exploration, and ultra-low temperature engineering fields.

Low-Temperature Performance Core Data
The introduction of phenyl (C₆H₅) groups in phenyl silicone rubber effectively disrupts the regularity of the siloxane main chain, inhibiting low-temperature crystallization and significantly lowering the glass transition temperature (Tg):
Glass Transition Temperature: Low-phenyl type can reach -140°C, medium-phenyl type is -120°C, and high-phenyl type can be as low as below -110°C.
Elasticity Retention Temperature: Maintains high elasticity in a -120°C environment, with no brittle fracture in a -196°C liquid nitrogen environment.
Brittleness Temperature: Superior to conventional rubbers (such as fluorosilicone rubber at approximately -50°C, and ethylene-propylene rubber at approximately -40°C), reaching below -115°C.
Dynamic Stiffness Stability: In the range of -75°C to 200°C, the dynamic stiffness change rate is less than 15%, meeting the thermal cycling requirements of precision seals. Typical Extreme Low-Temperature Application Scenarios
Phenyl silicone rubber-based materials have been engineered and deployed in the following high-reliability low-temperature systems:
Application System | Functional Requirements | Typical Material Grade and Performance Indicators
Spacecraft Docking Seals | Withstands -100°C vacuum low temperature, radiation resistance, zero leakage | China Aerospace 6710 grade, leakage rate <1×10⁻⁴ Pa·m³/s at -100°C
Liquid Hydrogen/Liquid Oxygen Storage Tank Seals | Resists ultra-low temperature fluid impact, anti-permeation, long-term sealing | Used in the propellant tank sealing system of Long March 5 and 7 rockets, withstands -253°C liquid hydrogen environment
Deep Space Probe Piping Systems | Withstands extreme temperature changes in space (-180°C to +120°C), resistant to cosmic rays | NASA and ESA use phenyl silicone rubber as a sealing material for pipe joints in various probes
Satellite Optical and Electronic Packaging | Maintains dielectric stability at low temperatures, low thermal shrinkage | Used in satellite-borne CCD sensor packaging, dimensional change rate <0.05% at -150°C
Aerospace Engine Insulation Layer | Remains flexible after low-temperature pre-cooling, works in conjunction with high-temperature layers | Acts as a transitional buffer layer in a multi-layer thermal protection system, mitigating thermal stress concentration
Comparison of Performance with Mainstream Low-Temperature Sealing Materials
Material System | Glass Transition Temperature (Tg) | Lowest Effective Use Temperature | Low-Temperature Elasticity Retention | Radiation Resistance | Vacuum Resistance | Applicable Scenarios
Phenyl Silicone Rubber | -140°C to -110°C | -196°C | Excellent (flexible at -120°C) | Excellent | Excellent | Aerospace sealing, deep space exploration, liquid hydrogen systems
Fluorosilicone Rubber | -50°C to -30°C | -50°C | Medium | Medium | Good | High-temperature fuel sealing, chemical valves
Ethylene Propylene Diene Monomer (EPDM) | -40°C to -30°C | -40°C | Good | Poor | Good | Automotive door and window seals, cooling systems
Natural Rubber | -50°C to -60°C | -50°C | Poor | Poor | Poor | Room temperature tires, cushioning pads
Fluororubber (FKM) | -20°C to 0°C | -20°C Poor  Medium  Good  High Temperature and High Pressure Oil Seal
Note: Phenyl silicone rubber exhibits significantly superior overall performance compared to other rubber systems in environments below -100°C. It is currently the only engineering elastomer material that can simultaneously provide low-temperature elasticity, radiation resistance, vacuum resistance, and self-extinguishing properties.

Technical Advantages and Engineering Value
Radiation Degradation Resistance: High phenyl content (>25%) materials can withstand 10⁶–10⁸ Gy gamma ray irradiation, suitable for long-term missions of deep space probes.
Self-Extinguishing: No molten droplets during combustion, and the flame self-extinguishes, meeting the flame retardant standards for materials in spacecraft cabins.
Low Volatility: Extremely low volatile matter in high vacuum environments, avoiding contamination of sensitive optical and electronic devices.
Stable Electrical Insulation: Dielectric constant change <5% at -196°C, suitable for low-temperature cable and sensor insulation layers.
Current Technical Bottlenecks and Development Directions
Despite its excellent performance, phenyl silicone rubber still faces the following challenges in extreme low-temperature applications:

High Processing Difficulty: High phenyl content leads to high viscosity and poor vulcanization flowability, requiring precision molding and high-temperature post-treatment.
High Cost: The price of phenyl monomer raw materials is 5–8 times that of ordinary silicone rubber, limiting its promotion in civilian applications.
Long-Term Creep Control: Under continuous low-temperature load, some formulations exhibit slow deformation, requiring optimization of crosslinking density and filler distribution.
Future research focuses on:

In-situ reinforcement with nano-silica: Improving low-temperature modulus and creep resistance;
Phenyl-fluorosilicone copolymer system: Combining the oil resistance of fluorine elements with the low-temperature properties of phenyl groups, extending its application to liquefied natural gas (LNG) sealing;
3D printing molding process: Enabling rapid prototyping of complex geometric low-temperature sealing components.
Phenyl silicone rubber has become an irreplaceable "low-temperature elastic cornerstone" in China's aerospace, deep space exploration, and ultra-low temperature engineering, and its performance boundaries are continuously expanding.