Temperature is the key factor affecting the insulation performance of cable accessories. In this paper

the infrared spectrum and glass transition characteristics of silicone rubber materials with different hardness are analyzed

and the dielectric properties

resistance properties and breakdown properties of the silicone rubber materials with different hardness for cable accessories are tested and analyzed under high and low temperature environment from -40 ℃ to +60 ℃. From the micro level

the influence mechanism of high and low temperature on the insulating property of silicone rubber is revealed by calculating and analyzing the free volume and mean-square displacement of silicone rubber at different temperatures. The research shows that with the increase of temperature

the relative dielectric constant of silicone rubber with hardness of 40 HA is decreased from 3.66 to 3.22

that is about 12%. In contrast

the relative dielectric constant of silicone rubber with hardness of 90 HA is decreased about 15%. The tangents of the dielectric loss angles of the two remain almost unchanged in the range of -40 ℃ to +60 ℃

with the average values of 1.46×10

-3

and 1.57×10

-3

respectively. The reason is that with the rise of temperature

the mean-square displacement of silicone rubber molecules increases

and the bound charge polarization process is hindered by the disordered movement. In addition

the increase of silica content can improve the dielectric constant of the silicon rubber with ha

rdness of 90 HA. With the rise of temperature from -40 ℃ to +60 ℃

the volume resistivity of the silicon rubber with hardness of 40 HA is decreased from 1.24×10

17

Ω·cm to 1.14×10

15

Ω·cm. At the same temperature

the volume resistivity of the silicon rubber with hardness of 90 HA is decreased by about 1 order of magnitude. This is mainly related to the carrier concentration due to temperature

mobility variation and the content of silica. With the rise of temperature from -40 ℃ to +60 ℃

the breakdown strength of the silicone rubber with hardness of 40 HA is decreased from 39.29 kV/mm to 23.98 kV/mm with reduction of approximately 39%

and that with hardness of 90 HA is slightly decreased at the same temperature. This is because the free volume of the silicone rubber increases with the increase of temperature

resulting in larger free travel of electrons

and more energy is obtained by free electron acceleration. At the same time

the introduction of silica as an impurity will lead to an increase of the breakdown probability of silicone rubber at the weak point. This work has guiding significance for abnormal analysis and performance improvement of cable accessories.