Cellulose-based binder assisted exfoliation of large-sized boron nitride nanosheets for improved thermal management capability of polymer films

Boron nitride nanosheets (BNNS) are widely used as fillers for flexible thermal interface materials due to their excellent thermal conductivity and insulating properties. However, the interfacial thermal resistance between the BNNS hinders the rapid transfer of heat from the electronics. Herein, we introduced a cellulose-based “binder” (ENC/CMC) into the ball milling process to assist in the exfoliation of h-BNNS with large-size structures. The micro-scale interfacial friction force and macro-scale mechanical shear stress greatly enhance exfoliation efficiency. The highly dispersed cellulose/h-BNNS dispersions were mixed with an aqueous PVA solution, and densified films were obtained by the sol-gel-film conversion process. Large-sized h-BNNS are uniformly arranged in the cellulose network, resulting in a strong mechanical architecture and continuous thermal conductivity pathways in the PVA matrix. Consequently, the ENC@h-BNNS/PVA-0.75 demonstrated thermal conductivity of up to 2.31 W/mK while achieving maximum tensile strength (168.4 MPa), which were increased by 950 % and 66.6 % over ENC/PVA film and showed excellent flexibility and thermal stability.