Polymer composites with expanded graphite network with superior thermal conductivity and electromagnetic interference shielding performance

• Thermal molding process fabricated composites with enhanced 3D expanded graphite (EG) network. • The enhanced 3D networks with small molecules showed low interface thermal resistance. • The EG/LLDPE-3D network composites exhibited an ultrahigh thermal conductivity of 19.6 Wm -1 K −1 . • The resulting composites had remarkable EMI shielding effectiveness. Polymer composites with high thermal conductivity and excellent electromagnetic interference (EMI) shielding are in high demand in modern microelectronic devices. However, for the most reported EMI shielding composites, high thermal conductivity is not easily achieved and the improvement efficiency is usually low due to the poor control over the heat transfer pathways. Herein, we developed a facile method to fabricate enhanced 3D expanded graphite (EG) network by pre-melt blending of EG with stearic acid and polyethylene wax, followed by powder mixing and thermal molding with linear low-density polyethylene (LLDPE) particles. It was found that micro gaps in EG were significantly reduced due to the introduction of small molecular compounds. The constructed continuous 3D networks and introduction of small molecular compounds in composite showed a much low interface thermal resistance and the thermal conductivity increased to ultrahigh levels which was greater than expected. The maximum thermal conductivity of composites increased from 8.6 Wm -1 K −1 to 19.6 Wm -1 K −1 with the presence of 24.89 vol% EG and the corresponding enhancement efficiency exceeded 5927% relative to neat LLDPE. The heat dissipation experiment revealed the high cooling efficiency of composite and the finite element simulation further visually confirmed the excellent heat-transfer capabilities. Moreover, the prepared composite exhibited excellent EMI shielding effectiveness (SE) of 52.4 dB and electrical conductivity up to 4000 Sm −1 . This work provides a facile, low-cost, and scalable method to fabricate high thermal conductive and EMI shielding materials by building enhanced 3D filler networks.