Superiority of dielectric properties of LDPE/MgO nanocomposites over microcomposites

Dielectric properties were compared between two kinds of low-density polyethylene (LDPE) composites prepared by adding near spherical MgO fillers with different diameters of around several ten nm and several m. In the whole range of temperature from 0°C to 90°C, the conductivity is decreased and the permittivity is increased by the addition of fillers, irrespective of their sizes. However, the decrement in the conductivity is more significant and permittivity increment is suppressed more in the case of the nm fillers. In addition, a drastic increase in dielectric loss factor, observed at low frequencies, is suppressed more significantly by the addition of the nm fillers. While the formation of packet-like charge, observed in LDPE, is suppressed by both fillers, the effect is far more significant in the nanocomposites. This means that the nano-fillers suppress the conductivity enhancement by the voltage application more effectively.