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.

Detection of compatibilizer efficiency in conductive polymer blends by impedance spectroscopy: Microstructure evaluation approach

“…The topographical bulges indicate the presence of CNT agglomerates, which are observed near the interphase of PP/EVA and in PP phase. 22,34 These AFM observations are consistent with the SEM image in Figure 3B.…”

“…The agglomeration of nanoparticles can create interfacial regions (interfaces between the polymer and nanoparticle surfaces) where a significant amount of charge can be stored and therefore causes more complexity in relaxation mechanisms in the system. 22 As it is observed in Figure 9, increase in PP-g-MA concentration expands the dc plateau due to the rise in the number of conductive networks within the insulating polymer and the reduction in the spacing between CNT particles and clusters. AC conductivity versus frequency data were fitted to obtain dc conductivity and also the S exponent which are given in Table 6.…”

“…In our previous study, the effect of mixing time of a conductive masterbatch (PP-g-MA/CNT) in a PP/EVA blend on the electrical behavior of the blend was investigated by EIS. 22 Here the role of compatibilizer at varying concentrations on electrical conduction mechanism has been studied by EIS in which the dispersion role and interfacial localization role of the compatibilizer will be discretized. It is seen for the first time that EIS can be used as a tool to evaluate the efficiency of a compatibilizer in a conductive polymer blend.…”