246 / 2018-09-24 19:47:32

Study on Electric Tree of Nano-SiO2 Polypropylene Composite Insulation Material

Polypropylene, SiO2, Nano-composite medium,Electric tree

Polypropylene has good heat and chemical resistance and good electrical insulation properties. It is widely used in electrical insulation. However, polypropylene is a solid insulating material. Its disadvantages are its strong brittleness and rigidity, poor toughness and cold resistance. Insufficient, showing low impact performance at low temperature, low thermal conductivity, easy to oxidize; and pure polypropylene if it is placed in a high electric field environment for a long time, it is easy to produce electric branches and lead to insulation aging, which makes polypropylene at high pressure the application in the field of insulation is greatly limited. Electric branch means that the electric field strength in the local area of the polymer insulation exceeds the electrical strength of the material, resulting in local breakdown, forming a small passage caused by the discharge, and the inside of the passage is empty, and there is a trace of carbon particles generated by the discharge on the tube wall. The branches are few and clearly visible, and thus form a dendritic discharge destruction channel. The addition of thermoplastic elastomer SEBS can improve the toughness and low temperature impact of polypropylene. Nano-SiO2 can inhibit the growth of electric tree branches, which provides a new idea for improving the overall performance of polypropylene.
The electrical aging characteristics of SiO2/SEBS/PP composite insulating materials with PP/SEBS and three different preparation processes were studied, which provided basic performance information for polypropylene cable engineering applications. SEM (Scanning Electron Microscopy) was used to observe the dispersion state of nano-SiO2 particles in composite polypropylene under different preparation processes. The results show that the nano-SiO2 in PP/SiO2+SEBS is mainly dispersed in PP phase and PP/SEBS interface, the nano-SiO2 in PP/SEBS+SiO2 is present in both PP and SEBS phases, while nano-SiO2 in SiO2/SEBS+PP is mainly present at the SEBS phase and PP/SEBS interface. The electric tree branching voltage and the growth process image information of each composite material were obtained by the electric tree branch observation system. The results showed that SiO2/SEBS/PP composites under different preparation conditions, PP/SiO2+SEBS were the best to inhibit the electrical branches. Secondly, PP/SEBS+SiO2. The worst is SiO2/SEBS/PP. The surface morphology of SiO2/SEBS/PP composites after electric branch growth was observed by SEM. The results show that there are many and large electrical branches passing through the SEBS phase. In the PP phase, the electrical branches develop along the PP chips. When the electric branch grows to the surface of SiO2, they bypasses SiO2 to continue to grow in the medium. According to the analysis, the effect of SEBS on the initiation and growth of electric branches in PP, and the inhibition of SiO2 on PP electric branches.
According to the analysis, SEBS promotes the initiation and growth of electric branches in PP. When SEBS is encountered during the growth of electric branches, the SEBS material itself is weak in resistance to electric branches, and the electric branches are not blocked in SEBS, develop more rapidly, and continue to grow after passing through SEBS. Inhibition of SiO2 on PP electric branches. The nano-SiO2 particles are dispersed in the medium. Since the inorganic sheet structure of SiO2 has a barrier effect on the growth of the electric branch, the electric branch can not penetrate the inorganic sheet when it grows to the surface of SiO2, and can only continue to grow in the medium by bypassing SiO2. A small number of branches of electric tree branches are added to the medium, so that the shape of the electric branches is gradually dense, forming a cluster-like electric tree.