Impact of organically modified montmorillonite clay nanofiller on free volume and electrical properties of the composites

Polymer nanocomposites are increasingly used in insulation applications for enhanced electrical properties. However, there are intricate parameters that control the properties of the polymer, and hence investigations are required. This paper attempts to correlate the electrical properties of Epoxy/Organically modified montmorillonite clay composites with the free volume resulting from the incorporation of the Organically modified montmorillonite clay filler of 2, 5, and 7 weight per cent (wt.%). Positron annihilation spectroscopy has been used to compute the fractional free volume and free volume. The free volume percentage is observed to increase with the incorporation of 2 and 5 wt.% and reduces at 7 wt.%. A similar trend is observed in the average size of free volume. The filler increases the AC electric breakdown strength by 20%, arc resistance by 5%, and comparative tracking index by 10% at 5 wt.%. Thermal conductivity is seen to increase marginally with the filler. The surfaces of the composites are hydrophilic at 2 and 7 wt.%, and at 5 wt.%, it is hydrophobic. Longer durations of water diffusion render the surfaces of the nanocomposites hydrophobic. Fourier transform infrared spectroscopy investigations reveal broadening of peak, increase in peak intensity and stretching of Si–O–Si bonds at 5 wt.% of filler due to exfoliation. An attempt has been made to understand the results of electrical parameters based on the results of positron annihilation lifetime spectroscopy and thermal conductivity.