A novel modified expanded graphite/epoxy 3D composite with ultrahigh thermal conductivity

Polymer-based composites with efficient thermal energy dissipation performance can be prospectively applied in electronics and military industry. However, significantly improving the thermal conductivity (TC) of polymer-based composites is still challenging. Herein, 3D sulfanilamide-modified expanded graphite/epoxy (EG-SA/EP) composites with interconnected filler network were successfully prepared by a pre-filling and hot-pressing method. Benefiting from the interconnected network, the composite with 70 wt% EG-SA demonstrated ultrahigh bulk TC of 98 W/m·K (which exceeds some commercially-used metals) and up to 44,445% TC enhancement efficiency. Meanwhile, the EG-SA/EP composites exhibited excellent electromagnetic interference shielding performance of 85 dB (which is sufficient to block 99.9999997% of incident radiation), high electric conductivity of 7153 S/m and excellent thermal infrared response capability (the time to raise surface temperature from 19 to 82 °C is only 3 s). As for the mechanism of heat transfer, the 3D structure of EG-SA maintained through epoxy pre-filling in EG-SA is the main reason for the significantly improved TC. This is because the new method enables EG-SA to build a unique dense interconnected network in composites in the subsequent hot-pressing process, but the traditional direct mixing method easily destroys the inherent micro-3D structure of EG. The above excellent performances endow the EG-SA/EP composites with huge potential application value.