Method of forming thermally and electrically conductive polyolefin-carbon nanomaterial composite having breakdown-induced electrical conduction pathways

A method of making a polyolefin-carbon nanomaterial composite, comprising:

• mixing graphene nanoplatelets with a low density polyethylene powder to form a mixture, wherein 95 wt % of the particles of the polyethylene powder have a particle size of less than 500 μm,
• ball milling the mixture in a high-energy shaker to form a composite powder,
• molding the composite powder to form a composite plate, and
• subjecting the composite plate to an AC voltage of 1 to 50 kV to form the polyolefin-carbon nanomaterial composite, wherein the AC voltage is applied to the composite plate through a needle electrode disposed inside the composite plate while the composite plate is disposed on a supporting ground electrode such that the needle electrode does not contact the supporting ground electrode and the supporting ground electrode and the needle electrode are separated by a distance of at least 30% of a thickness of the composite plate, and the supporting ground electrode, the composite plate, and the needle electrode are immersed in a non-conductive liquid medium,
• wherein the polyolefin-carbon nanomaterial composite has oriented electrically and thermally conductive pathways that comprise dendritic conductive channels in the polyethylene matrix which terminate at and originate from at least one selected from the group consisting of an exterior surface of the polyolefin-carbon nanomaterial composite, a channel created by the needle electrode, and a graphene nanoplatelet.