Impedance analysis, dielectric relaxation, and electrical conductivity of multi-walled carbon nanotube-reinforced silicon elastomer nanocomposites

Dielectric relaxation behavior of multi-walled carbon nanotube (MWCNT)-reinforced silicone elastomer nanocomposites has been studied as a function of filler loading in a wide frequency range (10(-1)-10(6) Hz). The effect of MWCNT loading on the real and imaginary parts of impedance is distinctly visible. The significant change in the impedance parameters on filler loading is explained on the basis of interfacial polarization in a heterogeneous medium and relaxation dynamics of polymer chains. The electrical modulus formalism has been used to investigate the conductivity and relaxation phenomena of the system. The frequency dependence of ac conductivity is explained using percolation theory. The existence of percolation phenomenon in the composites is discussed on the basis of electrical conductivity and morphology of the composites. The percolation threshold (as studied by electrical conductivity) occurs in the range of 4 phr of MWCNT loading. The scanning electron photomicrographs show agglomeration of the MWCNT above 4 phr concentration and formation of a continuous network structure.