Structural, thermal and dielectric behaviour of exfoliated graphite nanoplatelets (xGnP) filled EVA/EOC blend composites

Nano-composites of xGnP filled ethylene vinyl acetate (EVA)/ethylene-octene copolymer (EOC) (80–20) blend with 0, 1, 3, 5, 9, 11 wt % of xGnP were fabricated by solution casting followed by compression moulding. The room temperature X-ray diffraction (XRD) pattern and field emission scanning electron microscope (FESEM) of the investigated samples reflect distribution of exfoliated graphite nanoplatelets (xGnP) in the EVA/EOC matrix. The thermo-physical properties of the composites were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC analysis shows that with increase in xGnP contents, crystallisation temperature increase and act as a nucleating agent. TGA analysis data validates the stability of composites with increase in xGnP wt % in the composites. The dielectric and conducting behaviours of the studied samples were investigated by computer controlled impedance analyser within the frequency range of 100 Hz to 5 MHz. The room temperature relative permittivity (εr) value increases with rise in wt % of xGnP loading and achieved maximum at 9 wt % and then it falls. Similar behaviour also noticed in ac conductivity study. The nature of charge carriers in the composites were investigated by utilising non-destructive impedance spectroscopy technique. The theoretical fitting of experimental data of Nyquist plot reveals all the compounds perform the bulk behaviour. Additionally, ac conductivity study validates Johnsher’s universal power law which confirms motions of the charges are translational one. I ∼ V characteristics of the studied samples were carried out by using Keithly electrometer which confirms that conduction behaviour was non-Ohmic at lower wt % xGnP loading but Ohmic conduction was achieved at higher wt % xGnP loading. From both impedance and I ∼ V study we have also confirmed the increases in conductance with increase in wt % of xGnP loading and shows similar phenomena as observed in dielectric study.