Employing impedance spectroscopy to investigate electrical conduction mechanism in polymer composite blends containing conductive masterbatch: PP/EVA/ (PP-g-MA/MWCNTS)

Abstract

Impedance spectroscopy analysis has been employed to investigate the effect of melt mixing time on electrical conduction mechanism, direct contact or electron tunneling, of a polymer blend using a conductive masterbatch. A novel approach is proposed to correlate the dispersion/distribution states of conductive nanoparticles within the phases, achieved through kinetic control of the conductive masterbatch, and their impedance properties. A blend of polypropylene and ethylene-vinyl acetate copolymer (PP/EVA) was considered as a case study for the matrix. An electrically conductive masterbatch of multiwalled carbon nanotubes (MWCNTs) in polypropylene-grafted-maleic anhydride (PP-g-MA) was added to the blend. The masterbatch in varying amounts was mixed with PP/EVA in a range of 1 min–4.5 min. The co-continuous morphology of the ternary polymer blend was validated via scanning electron microscopy micrographs. The atomic force microscopy (AFM) results showed that as the mixing time of the masterbatch increases the interconnected structures within the conductive interphase decrease. Impedance spectroscopy using alternating current was employed to probe the conduction mechanism in the composite blends. The impedance spectroscopy results revealed that for samples with low mixing time, a dielectric relaxation peak occurs at high frequencies due to the existence of more conductive pathways as a consequence of the interconnected structures of the masterbatch phase. Also, the major contribution of conductance was direct contact in the samples with low mixing times while electron tunneling mechanism was considerable for the samples with high mixing times. Dielectric constant was increased as a result of interfacial polarization boosting with mixing time. The percolation threshold was considerably decreased from 0.95 v% for simultaneous direct mixing method to 0.16 v% for the masterbatch method.