The verification of the temperature resistance limit of phenyl silicone oil in aircraft engine bearing lubrication requires a comprehensive analysis of its molecular structure characteristics, thermal stability test data and actual working condition simulation results. The following are specific verification paths and key conclusions:

1. Molecular structure and temperature resistance mechanism of phenyl silicone oil
Correlation between phenyl content and thermal stability
The temperature resistance of phenyl silicone oil is mainly determined by the molar fraction of phenyl substituents. Silicone oil with low phenyl content (such as 5%-10%) still maintains fluidity at -70°C and is suitable for extremely low temperature environments; while silicone oil with high phenyl content (such as phenyl molar fraction ≥50%) has significantly improved thermal oxidation stability and can be used for a long time at above 300°C. For example, a certain type of high phenyl silicone oil has been tested to work continuously at 320°C, and its thermal decomposition temperature is 60% higher than that of ordinary silicone oil.
Antioxidation and radiation resistance
The introduction of phenyl groups enhances the antioxidant capacity of silicone oil, making it less prone to crosslinking or degradation at high temperatures. Experimental data show that the oxidation induction period of phenyl silicone oil at 300°C is significantly prolonged, and it can withstand a radiation dose of 10⁶ Gy, meeting the protection requirements of nuclear power plants, indirectly proving its stability in the high-temperature radiation environment of aircraft engines.

2. Laboratory verification method for temperature resistance limit
Thermogravimetric analysis (TGA)
The thermal decomposition behavior of phenyl silicone oil in nitrogen or air atmosphere is tested by TGA. Typical results show that the mass loss rate of high phenyl content silicone oil is less than 5% at 350°C, while ordinary silicone oil decomposes significantly at 250°C.
Rotating oxygen bomb test (RBOT)
Simulate high-temperature oxidation environment and measure the oxidation induction time of silicone oil. The oxidation induction time of phenyl silicone oil at 150°C can be more than 3 times that of ordinary silicone oil, proving its antioxidant performance advantage.
High-temperature tribology test
The lubrication performance of silicone oil is tested by simulating bearing working conditions on a high-temperature friction tester. The results show that phenyl silicone oil can still maintain a low friction coefficient (μ≤0.12) at 300°C, and the wear volume is significantly lower than that of base silicone oil.

3. Temperature resistance limit under actual working conditions
Analysis of working conditions of aircraft engine bearings
The working temperature of modern aircraft engine bearings can reach 250℃-350℃, and they need to withstand high loads and high-speed rotation. For example, the surface temperature of the high-pressure turbine bearing of a certain type of turbofan engine can reach 320℃, and the lubricant is required to have long-term stability at this temperature.
Bench test and installation verification
The viscosity change, evaporation loss and metal wear of phenyl silicone oil at high temperature are monitored through engine bench test. Data show that after a certain type of high-phenyl silicone oil has been running continuously for 500 hours at 300℃, the viscosity change rate is ≤10%, and the metal wear is 40% lower than that of the basic silicone oil.
Failure case analysis
A certain type of aircraft engine failed due to high-temperature carbonization of lubricating oil. After switching to phenyl silicone oil, no carbonization phenomenon occurred after running for 2000 hours under the same working conditions, proving that its temperature resistance limit meets actual needs.

4. Boundary conditions of temperature resistance limit
Balance between temperature and viscosity
The viscosity of phenyl silicone oil decreases with increasing temperature, but high phenyl content can slow down the rate of viscosity decrease. For example, the kinematic viscosity of a certain type of silicone oil is 50 cSt at 200°C, and it remains above 10 cSt at 300°C, meeting the lubrication requirements of bearings.
Impact of additives
The temperature resistance limit of phenyl silicone oil can be further improved by adding antioxidants, extreme pressure agents, etc. For example, after adding 0.5% of hindered phenol antioxidants, the oxidation induction time of silicone oil at 350°C is extended by 50%.
Adaptability to working conditions
In environments with high temperature and humidity or corrosive media, the temperature resistance limit of phenyl silicone oil may decrease. Its performance needs to be guaranteed by measures such as sealing design or adding rust inhibitors.

5. Conclusion and Suggestions
Conclusion on temperature resistance limit
Based on laboratory data and actual working conditions, the temperature resistance limit of phenyl silicone oil can reach 320°C-350°C (short term) or 300°C (long term), which is significantly better than ordinary silicone oil.
Application suggestions
Silicone oil with high phenyl content: suitable for high-temperature bearing lubrication, such as high-pressure turbine bearings of aircraft engines.
Composite formula design: Improve comprehensive performance by adding antioxidants, extreme pressure agents, etc.
Working condition monitoring: Regularly test the viscosity, acid value and metal content of the lubricating oil to ensure its stable performance.
Future research direction
Develop a new phenyl silicone oil structure to further improve its thermal stability and antioxidant capacity.
Study the compatibility of phenyl silicone oil with other lubricating media to expand its application under complex working conditions.