Preparation of boron nitride nanosheets via polyethyleneimine assisted sand milling: towards thermal conductivity and insulation applications.

Hexagonal boron nitride (h-BN) is often used as a filler in polymer composites due to its good thermal conductivity and insulation properties. However, the compatibility between h-BN and the matrix limits its application areas. To overcome this issue, a combination of mechanical liquid phase exfoliation and chemical interfacial modification was adopted in this work. Polyethyleneimine (PEI) was used as the exfoliation reagent to prepare PEI-functionalized h-BN nanosheets, denoted as PEI@BNNS. Thermoplastic polyurethane (TPU) composites with different contents of h-BN and PEI@BNNS which were recorded as h-BN/TPU and PEI@BNNS/TPU were successfully prepared through a hot-pressing process, respectively. The results show that PEI@BNNS/TPU composites have better in-plane thermal conductivity while maintaining insulation, and with the content of 5 wt% PEI@BNNS, the in-plane thermal conductivity of the PEI@BNNS/TPU composite is up to 0.61 W m -1 K -1 , which is three times that of pure TPU (0.22 W m -1 K -1 ).