Dielectric, electrical, and rheological characterization of graphene-filled polystyrene nanocomposites

Abstract

A series of nanographene filled polystyrene (GPS) nanocomposites was prepared by in situ polymerization of styrene in the laboratory. The concentration of graphene was changed in the step of 0.25 wt% and a total of eight composites (including control) were prepared to obtain a threshold concentration of graphene. These composites, prepared by in situ polymerization followed by compression moulding, were characterized for their structural (using XRD), morphological (SEM), thermal (DSC, TGA, DTGA), dielectric behavior (ɛ', ɛ''') and DC conductivity. It was observed that the thermal stability as well as electrical and rheological properties of graphene-polystyrene nanocomposites significantly improved due to the homogeneous dispersion, intercalation and exfoliation of the graphene layers in the Polystyrene matrix. It was also observed that at room temperature dielectric constant (ε′) decreased with increasing concentration of graphene and reached a minimum at a certain filler concentration of 0.25 wt% (PSG025) when frequency is kept constant. Rheological study showed an improvement in the storage modulus (G′) with incorporation of graphene as nanofiller. Loss modulus (G′) and complex viscosity (η*) also increased with increasing graphene weight percentage. Relaxation time also increased at high graphene loading because of the pseudo-solid like behavior of polymer melt. POLYM. COMPOS., 34:2082–2093, 2013. © 2013 Society of Plastics Engineers