Facile transformation of graphite composites into their porous analogues with superior electrical, thermal, and EMI shielding properties

Abstract

Novel porous conducting polymer composites were prepared through the direct expansion of expandable graphite within a melted polypropylene matrix. A facile in-situ method resulted in a remarkable reduction in the electrical percolation threshold of composites containing expanded graphite, forming an accordion-like network inside the polymer matrix compared to their non-expanded compact analogues. Despite their porosity, the expanded samples showed increased thermal conductivity, and the variation of electrical and thermal conductivity with the filler concentration adhered to the percolation theory and Lichtenecker model, respectively. Depending on the concentration, the expansion process notably enhanced the electromagnetic interference (EMI) shielding efficiency, producing a composite with shielding performance above 20 dB. The presented strategy enables a facile and cost-effective improvement of the electrical, thermal, and EMI shielding properties without affecting the weight of the composite, making it highly relevant for industrial adoption.