Low percolation threshold and enhanced electrical and dielectric properties of graphite powder/poly (vinyl alcohol) composites

Polyvinyl alcohol (PVA) composites with a conductive filler, graphite powder (GP) were prepared by solution casting process. GP remains well dispersed in the PVA composites as evidenced by the lack of the characteristic graphite reflection in the composites. SEM imaging show smooth fractured surfaces with graphite stacks and obvious debonding from the matrix in the GP/PVA composites. The dielectric dispersion and AC conductivity of the composite system exhibited a strong frequency dependence particularly in the vicinity of percolation threshold (f_c ∼ 6 wt% = 2.65 vol%). A 150 times increase of dielectric permittivity and seven orders of magnitude higher conductivity were obtained by adding 2.65 vol% graphite powder in PVA indicating the efficient loading between the graphite and the matrix at percolation threshold which is well above the percolation threshold (f_c = 0.41 vol%) for PVA/GOnP composites. Moreover, the dielectric properties were measured at about 30°C and 1 kHz. The values of permittivity and dielectric loss were found to increase with increasing graphite content. The percolative composites exhibit very low dielectric loss and leakage current density. Such GP/PVA flexible composites in tailored form might be important for many printing circuit board and capacitor applications in the age of device miniaturization. POLYM. COMPOS., 39:4400–4407, 2018. © 2017 Society of Plastics Engineers