A method of forming a polyolefin-carbon nanomaterial composite which contains oriented electrically conductive pathways. The method involves milling a polyolefin with particles of a carbon nanomaterial, molding to form a composite plate, and subjecting the composite plate to an AC voltage. The AC voltage forms oriented electrically conductive pathways by partial dielectric breakdown of the composite. The presence of the oriented electrically conductive pathways gives the polyolefin-carbon nanomaterial electrical and thermal conductivity higher than the polyolefin alone.