Analysis of Thermal Conductivity of Silicone Oil and Its Influencing Factors
Basic properties of silicone oil
Silicone oil is a type of organic silicon polymer based on polydimethylsiloxane (PDMS), which has chemical inertness, wide temperature range stability (-50℃ to 200℃), low viscosity temperature coefficient and excellent electrical insulation. Its thermal conductivity is usually lower than that of metal or water, but can be significantly improved through modification.
Thermal conductivity range
The thermal conductivity of silicone oil is generally between 0.1–0.2 W/(m·K), and the specific value is affected by the following factors:
Molecular weight and viscosity: Low viscosity silicone oil (such as 10 cSt) has a thermal conductivity of about 0.1 W/(m·K), and high viscosity (1000 cSt) may slightly increase to 0.15 W/(m·K).
Temperature: As the temperature increases, the thermal conductivity increases slightly (for example, 0.12 W/(m·K) at 20°C and 0.18 W/(m·K) at 100°C).
Additives: Adding thermal conductive fillers (such as Al₂O₃, ZnO) can increase it to 0.5–2 W/(m·K), forming thermal conductive silicone grease or composite silicone oil.
Test methods and standards
Thermal conductivity is usually measured by the transient hot wire method (ASTM D7896) or the steady hot plate method (ASTM D5470). Please note that the transparency of silicone oil may affect the accuracy of the optical test method.
Thermal conductivity requirements in industry applications
Electronic cooling: Pure silicone oil has insufficient thermal conductivity, and filled silicone grease is required (such as silicone oil containing BN with a thermal conductivity of 1.5 W/(m·K)).
Heat transfer medium: In high-temperature systems, modified silicone oil can be used as a stable liquid phase heat transfer carrier.
Data reference (typical value)
Type Thermal conductivity (W/(m·K)) Temperature conditions
Pure PDMS silicone oil (50 cSt) 0.13 25℃
Al₂O₃ filled silicone oil (20%) 0.45 25℃
High phenyl silicone oil 0.17 100℃
Ways to improve thermal conductivity
Chemical modification: Introduce polar groups such as phenyl to enhance intermolecular forces.
Physical blending: Add nanodiamond (≤1% can increase by more than 30%).
Note: The thermal conductivity of silicone oil is much lower than that of water (0.6 W/(m·K)) or mineral oil (0.15–0.3 W/(m·K)). In high-temperature applications, its thermal stability and viscosity change need to be comprehensively evaluated.
