Study On Breakdown Characteristics Of Acetylated SEBS/LDPE Composites

Polyethylene(PE)is widely used in the power field due to its excellent processing and insulation properties.As the voltage level of the UHV grid system in China continues to increase,the requirements for the breakdown performance of the polymer also increase.It is of great significance to study the breakdown mechanism of polymer materials.In this paper,acetylated SEBS(Ac-SEBS)was constructed by acetylation reaction on styrene-ethylene-butadiene-styrene(SEBS)molecular chain to form acetophenone groups,and melt-blended with pure LDPE to prepare Ac-SEBS./LDPE composite.DC and AC breakdown field strength tests were performed on pure LDPE and Ac-SEBS/LDPE composites.The results show that the DC breakdown field strength of Ac-SEBS/LDPE composites is significantly higher than that of pure LDPE,but the variation of AC breakdown field strength is not obvious.In this paper,the temperature in the factors influencing the field strength and the rate of increase of the applied electric field are deeply explored.The test analyzes the influence of temperature changes in different temperature zones on the AC/DC breakdown field strength and the main mechanism leading to breakdown.The results show that in the low temperature region,the DC breakdown field strength does not change significantly with the increase of temperature,and the main breakdown mechanism is electrical breakdown.In the high temperature region,the DC breakdown field strength decreases sharply with the increase of temperature,and the main breakdown mechanism for heat breakdown.The field strength of the AC breakdown decreases with increasing temperature,the change in the low temperature region is small,the temperature in the middle temperature region decreases,and the temperature in the high temperature region decreases more severely,indicating that the effect of internal heat of the material is more obvious under the action of AC voltage.The experimental study on the DC breakdown field strength under different applied electric field rising rates.The results show that the DC breakdown field strength increases with the increase of the electric field rising rate.When the temperature is low,the DC breakdown field strength does not change much with the increase of the electric field.When the temperature is high,the DC breakdown field strength increases with the electric field.The increase in rate is significantly increased.The crystallinity of pure LDPE and Ac-SEBS/LDPE composites were tested.The results show that the crystallinity of the composites decreases with the addition of Ac-SEBS.In this paper,the basic electrical properties of pure LDPE and Ac-SEBS/LDPE composites were tested and analyzed in combination with the breakdown mechanism.Firstly,the space charge distribution characteristics of pure LDPE and Ac-SEBS composites were tested.It was found that Ac-SEBS can suppress the space charge inside the material.Secondly,the conductance of pure LDPE and Ac-SEBS/LDPE composites at different temperatures.Behavior,polarization behavior and dielectric loss were tested.It was found that the electrical conductivity of Ac-SEBS/LDPE composites was significantly lower than that of pure LDPE.At high temperatures,the electrical conductivity flow increased exponentially,and the dielectric loss increased first and then decreased.