Effect of Multiple Mixing on Dispersion and DC Electrical Properties of SiO2/LDPE Nanocomposites

The nano SiO2/low density polyethylene(LDPE) composites were multiple mixing by a parallel twin-screw extruder, the effect of the process on the dispersion and DC breakdown strength and space charge characteristics of nano SiO2 particles in nano SiO2/ LDPE composite system were tested. SEM results show that with the increase of mixing times, nano SiO2 particles are dispersed more uniformly in the LDPE; DC breakdown strength of multiple mixing increases to 433.1kV/mm at room temperature compared with single mixing; With the increase of mixing times, the ability to suppress space charge becomes stronger at low temperature, but the inhibition ability becomes worse at high temperature above 60 degrees C. TSC results showed that the TSC peak of SiO2/ LDPE prepared by multiple mixing also increased significantly around 40 degrees C - 70 degrees C, which indicated that a large number of residues were generated due to the material degradation caused by the mechanical shearing. The FTIR test confirm the presence of degradation. The increase of defect directly leads to the increase of space charge density, the increase of structural defects affects the space charge suppression performance in the high temperature region of nano SiO2/LDPE composites.