What factors are related to the dielectric strength of power silicone?

What factors are related to the dielectric strength of power silicone?
The dielectric strength of power silicone is related to many factors, and the following is a detailed introduction:
Material composition and formula:
Base polymer: The molecular structure and purity of the base polymer of power silicone, such as polydimethylsiloxane, will affect the dielectric strength. Base polymers with high purity and regular molecular structure can reduce internal conductive defects and help improve dielectric strength.
Filler: The type and content of added fillers have a significant impact on dielectric strength. Inorganic fillers with high dielectric constants such as silica and alumina can be evenly dispersed in the silicone matrix when added in appropriate amounts, enhancing the overall insulation performance and improving dielectric strength. However, if the filler is unevenly dispersed or used in excessive amounts, air gaps or impurities may form inside the silicone, which will reduce the dielectric strength.
Additives: Some additives such as coupling agents can improve the interfacial bonding between fillers and matrix, making fillers play a better role and indirectly affecting dielectric strength; while some additives such as flame retardants, if improperly selected or added in unreasonable amounts, may introduce conductive impurities or change the microstructure of silicone, which has a negative impact on dielectric strength.
Production process:
Mixing uniformity: In the preparation process of silicone, it is crucial whether the components such as base polymer, filler and additives are mixed evenly. Uneven mixing will lead to local differences in dielectric properties and weak points, which are prone to electrical breakdown in these areas, thereby reducing the overall dielectric strength.
Curing conditions: Curing temperature and time have a great influence on the microstructure and cross-linking degree of silicone. Appropriate curing temperature and time can make silicone form a dense and uniform network structure and improve dielectric properties; if the curing temperature is too high or the time is too long, the silicone may be over-cross-linked, causing the material to become brittle, internal stress and defects, and reducing dielectric strength; and insufficient curing will cause unreacted groups and voids inside the silicone, which is also not conducive to the improvement of dielectric properties.
Degassing: If the degassing is not done sufficiently during the production process, bubbles or voids will remain inside the silicone. The dielectric constant of these air gaps is much lower than that of the silicone matrix. Under the action of the electric field, the electric field strength in the air gap will be concentrated, which is easy to cause local discharge, and then lead to a decrease in dielectric strength.
Working environment:
Temperature: Temperature has a significant effect on the dielectric strength of power silicone. Within a certain range, as the temperature rises, the thermal motion of silicone molecules intensifies, the distance between molecules increases, the migration of electrons becomes easier, and the dielectric strength gradually decreases. When the temperature is too high, the silicone may undergo thermal degradation, destroying its molecular structure and insulation properties.
Humidity: Increased ambient humidity will cause moisture to be adsorbed on the surface of the silicone, and water molecules may penetrate into the inside of the silicone, forming a conductive channel or reducing local insulation properties. Especially in a high humidity environment, moisture will form a water film on the surface of the silicone, resulting in an increase in surface leakage current and a decrease in dielectric strength.
Electric field frequency: Under an AC electric field, the dielectric strength of power silicone will be affected by the frequency of the electric field. As the frequency increases, the dielectric loss inside the silicone increases, the heat generated increases, and the dielectric strength decreases. At different frequencies, the polarization and conductivity of silica gel will also change, thus affecting its ability to withstand electric fields.
Sample thickness: Generally speaking, under the same material and test conditions, the dielectric strength will decrease as the sample thickness increases. This is because the probability of defects and impurities inside thicker samples is relatively high. Under the action of the electric field, these defects are more likely to develop into penetrating conductive channels, resulting in electrical breakdown and a decrease in the average dielectric strength.