There are significant differences in high-temperature dielectric properties between phenyl silicone oil and polyimide composite film. Polyimide composite film usually shows better dielectric strength, stability and temperature resistance range, while phenyl silicone oil has unique advantages in lubrication, liquid sealing and other scenarios, but the dielectric properties are greatly affected by temperature. The following analysis is carried out from the perspectives of performance characteristics, high-temperature dielectric performance comparison, and application scenarios:

1. High-temperature dielectric properties of phenyl silicone oil
Temperature resistance range and stability
Phenyl silicone oil can still maintain certain dielectric properties at high temperatures, but its temperature resistance range is usually lower than that of polyimide composite film. The gelation time of phenyl silicone oil in 250℃ hot air is 1750 hours, indicating that it has good thermal stability at this temperature. However, when the temperature exceeds 300℃, the viscosity of phenyl silicone oil will increase significantly, the oxidation reaction will intensify, and the dielectric properties will decrease.
Phenyl silicone oil has excellent low-temperature resistance, and low-phenyl silicone oil is still fluid at -70℃, which is suitable for use in extreme low-temperature environments. However, in high temperature environments, its dielectric loss will increase with increasing temperature, affecting its performance in high-frequency circuits.
Dielectric constant and loss
The dielectric constant of phenyl silicone oil is usually between 2.6 and 3.0, and the dielectric loss tangent is ≤1×10⁻³ at 25°C and 50Hz. As the temperature rises, the dielectric loss will increase significantly, resulting in reduced signal transmission efficiency.
The breakdown strength of phenyl silicone oil is greater than 45 kV/2.5 mm at 25°C and 50Hz, but its breakdown strength will decrease at high temperatures, limiting its application in high voltage and high temperature environments.
Application scenarios
Phenyl silicone oil is mainly used in lubrication, heat exchange fluid, insulating oil, gas-liquid chromatography carrier and other fields. In electronic and electrical equipment, phenyl silicone oil can be used as high and low temperature lubricant or heat carrier, but the limitations of its dielectric properties make it unsuitable as a core insulating material.

2. High-temperature dielectric properties of polyimide composite films
Temperature range and stability
Polyimide composite films have excellent high-temperature resistance, with long-term use temperatures of more than 300°C and short-term tolerance of 500°C. Its thermal decomposition temperature usually exceeds 500°C, and the thermal decomposition temperature of some varieties can reach 600°C. It is one of the materials with the highest thermal stability among known organic polymers.
Polyimide composite films can still maintain low dielectric loss and high dielectric strength at high temperatures, and are suitable for use as insulating materials in extreme high temperature environments.
Dielectric constant and loss
The dielectric constant of polyimide is usually around 3.4, which can be further reduced to around 2.5 by introducing fluorine atoms or nanofillers (such as graphene and strontium titanate). Its dielectric loss is in the order of 10⁻³, the dielectric strength can reach 100~300 kV/mm, and the volume resistivity is 10¹⁵~10¹⁷ Ω·cm.
The dielectric stability of polyimide composite film at high temperature is better than that of phenyl silicone oil, and it is suitable as an insulating material in high-frequency electronic devices, flexible circuit boards, chip packaging and other fields.
Application scenarios
Polyimide composite film is widely used in aerospace, electrical and electronic, chemical pipelines, seals and other fields. In the field of electronics, polyimide film can be used as a base material for flexible circuit boards, an insulating layer for chip packaging, motor slot insulation and cable wrapping materials. Its excellent high temperature resistance, corrosion resistance and dielectric properties make it an ideal insulating material in high temperature environments.