Space charge evolution in polypropylene loaded with synthetic and natural nanoclay aged at 50 °C temperature

The evolution of space charges in Polypropylene (PP) filled with synthetic and natural nanoclay after aging with -25 kV/mm DC field under 50 °C were investigated. Following certain periods of aging, the space charge was measured by the PEA technique. The PP materials, bases for the two types of Polymer nanocomposites, i.e. PP were loaded with synthetic and natural nanoclay. The unfilled PP contains grafted maleic anhydride as compatibilizers. It was observed that the percentage amount of compatibilizers affects the charge distribution in the PP materials. The results indicated that aging with 50 °C temperature of the PNC with 2 and 4-wt% synthetic clay stocks high quantity of charges compared to the other filled materials. These two concentrations could not be optimal for aging under 50 °C. Insignificant accumulation of space charge and independent from aging time was observed for the PP loaded with 2-wt% of natural clay. This could be due to the smaller aspect ratio of natural nanoclay platelets compared to the synthetic nanoclay platelets. The clay platelets limit the molecular motion in the amorphous phase due to the interaction between the platelets and PP matrix. But, more work is required to investigate the effect of the percentage of compatibilizers on the charge accumulation property. Highly doped PNCs like the PP1-S8% and PP2-N6% can enhance overlapping of the diffuse double layer charge clouds around nanoparticles and promote movement of space charges, thereby leading to a sharp increase of the conductivity of PNCs.