The optimization of the thermal conductivity of high-temperature resistant phenyl silicone oil needs to be carried out from four dimensions: molecular structure design, filler compounding, process improvement and performance balance. The following is the specific technical path and analysis:

1. Molecular structure design and optimization
Phenyl content regulation
The introduction of phenyl can improve the temperature resistance and thermal conductivity of silicone oil, but the phenyl content needs to be controlled within a reasonable range (such as 30%-50%). Excessive phenyl content will cause a significant increase in viscosity, affecting processing performance. For example, the thermal conductivity of silicone oil with a phenyl content of 30% at 25°C is 0.18W/(m·K), while it increases to 0.22W/(m·K) at 50% phenyl content, but the viscosity may increase tenfold.
Endcapping agent selection
The use of specific endcapping agents such as methyl diphenylsilyl can improve thermal stability, but structures that reduce thermal stability such as triphenylsilyl need to be avoided. Suitable endcapping agents can reduce molecular chain breakage at high temperatures and maintain the stability of thermal conductivity.
Molecular weight distribution control
Controlling molecular weight distribution (PDI) through balanced polymerization technology, reducing the generation of low molecular weight rings, and improving the uniformity of thermal conductivity. Excessively wide molecular weight distribution will cause thermal conductivity fluctuations and affect overall performance.

2. Filler compounding and interface modification
High thermal conductivity filler compounding
Adding high thermal conductivity fillers such as boron nitride and alumina can significantly improve thermal conductivity. For example, when the boron nitride content reaches 30wt%, the thermal conductivity of the composite material can reach 1.8W/(m·K), which is nine times that of pure silicone oil. The shape (such as flake) and size of the filler are crucial to the formation of the thermal conductivity path.
Interface coupling technology
Modifying the filler surface through silane coupling agent, enhancing the interface bonding force with phenyl silicone oil and reducing the interface thermal resistance. For example, ultrasonic treatment combined with silane coupling agent can increase the thermal conductivity network formation rate to 85%.
Nanoparticle dispersion technology
When using particles such as nano boron nitride, the problem of dispersion uniformity needs to be solved. Through surface modification or solvation treatment, nanoparticle agglomeration can be avoided to ensure the continuity of the thermal network.

3. Process optimization and modification technology
Thermal history treatment
Thermal history treatment (such as annealing) of phenyl silicone oil can promote the orderly arrangement of molecular chains and improve thermal conductivity. Experiments show that the thermal conductivity can be increased by about 8% after thermal history treatment.
Blending modification
Blending phenyl silicone oil with other high thermal conductivity silicone oils (such as fluorosilicone oil) can achieve complementary performance. For example, the low surface energy characteristics of fluorosilicone oil can improve lubricity while maintaining high thermal conductivity.
Cross-linking network construction
By introducing a cross-linking agent (such as hydrogenated silicone oil and styrene addition reaction), a three-dimensional network structure is formed to improve thermal conductivity and mechanical strength. The degree of cross-linking needs to be controlled within a reasonable range to avoid excessive viscosity.

4. Performance balance and application optimization
Trade-off between viscosity and thermal conductivity
Although high phenyl content can improve thermal conductivity, it will cause a sharp increase in viscosity. It is necessary to select the appropriate phenyl content according to the application scenario (such as LED heat dissipation, transformer oil) to balance thermal conductivity and processing performance.
Improved low-temperature fluidity
In low-temperature environments, the viscosity of phenyl silicone oil will increase significantly. The low-temperature viscosity can be reduced by adding a pour point depressant (such as polymethacrylate) to ensure that the kinematic viscosity at -30°C meets the application requirements.
Long-term thermal stability test
The thermal conductivity attenuation of phenyl silicone oil is evaluated through accelerated aging experiments (such as 150°C for 1000 hours). The experiment shows that the thermal conductivity attenuation of the optimized phenyl silicone oil can be controlled within 5%.