Phenyl silicone, as a high-performance silicone material, plays a key role in ablation-resistant sealing technology for spacecraft re-entry. The following is a detailed analysis of this technology:

I. Basic Performance Characteristics of Phenyl Silicone
[Temperature Range]:
Ordinary silicone typically has a temperature range of -40°C to 160°C.
Phenyl silicone's temperature range can be extended to -70°C to 350°C. Short-term operating temperatures can even reach -110°C to 400°C.

[Thermal Stability]:
The introduction of the phenyl group effectively prevents oxidative decomposition of side chain groups at high temperatures. The phenyl group forms a π-coordinate structure with silicon, inhibiting the oxidation of polymer side groups to form alkoxy radicals at high temperatures. It can operate for long periods at 180°C and withstand temperatures of 200°C for weeks or longer while maintaining flexibility.

[Special Properties]:
It has excellent Radiation resistance, ablation resistance, and resistance to atomic oxygen in space
Excellent resistance to thermal cycling and vibration
Maintains structural integrity under extreme temperature fluctuations

II. Phenyl Silicone Product Categories:
Low-phenyl silicone rubber (phenyl content 5%-15%)
Medium-phenyl silicone rubber (phenyl content 15%-25%)
High-phenyl silicone rubber (phenyl content 30% or more) offers the best ablation resistance

III. Ablation Resistance Mechanism and Performance Comparison
Ablation Mechanism:
Phenyl groups inhibit the oxidation of polymer side groups at high temperatures
Forming a π-coordinated structure improves thermal stability
Maintains structural integrity under extreme environments

Performance Comparison:
Performance Indicators Ordinary silicone rubber, phenyl silicone rubber
Temperature range: -40°C to 160°C, -70°C to 350°C
Short-term temperature resistance: 200°C to 400°C
Ablation resistance: Average to Excellent
Radiation resistance: Average to Excellent
Low-temperature performance: -55°C to -73°C

Compared to other materials:
Compared to fluorosilicone rubber, phenyl silicone rubber has a wider operating temperature range.

IV. Relevant Standards and Test Methods
National Standard:
GB/T 42047-2022 "Determination of Outgassing Products from Materials and Components in Sealed Compartments of Manned Spacecraft"
QJ 1035.1-1986 "O-Ring Rubber Seal Standard"

Performance Tests:
High-Temperature Sealing Performance Test: High-Temperature Stability, Seal Failure Point Determination Under Different Temperature Gradients
Low-Temperature Sealing Performance Test: Low-Temperature Shrinkage Behavior, Elasticity Retention at Ultra-Low Temperatures
Compressive Strength Test: Leakage Resistance Under Multiple Pressures

Special Aerospace Requirements:
Must Pass 3000°C High-Temperature Flame and -269°C Deep Freeze Tests
Ability to Withstand High Radiation Fields (Geosynchronous Orbit Annual Radiation Level >10⁶) rad)
Maintaining performance in microgravity and high-frequency vibration

V. Technical Challenges and Development Trends
Current Challenges:
High-phenyl silicone rubber (phenyl content >30%) is difficult to process and has poor physical and mechanical properties.
Long-term stability under extreme temperature gradients needs to be improved.

Development Trends:
Developing specialty silicone rubbers with higher phenyl content
Improving processing techniques to enhance mechanical properties
Researching new composite sealing materials that combine the advantages of multiple materials

Due to its excellent high and low temperature resistance, ablation resistance, and radiation resistance, phenyl silicone has become an ideal choice for spacecraft re-entry sealing technology. With advances in materials science, its performance and application range will continue to expand.