Flexible and Robust Functionalized Boron Nitride/Poly(p-Phenylene Benzobisoxazole) Nanocomposite Paper with High Thermal Conductivity and Outstanding Electrical Insulation

Abstract

With the rapid development of 5G information technology, thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent. In this work, "high-temperature solid-phase & diazonium salt decomposition" method is carried out to prepare benzidine-functionalized boron nitride (m-BN). Subsequently, m-BN/poly(p-phenylene benzobisoxazole) nanofiber (PNF) nanocomposite paper with nacre-mimetic layered structures is prepared via sol-gel film transformation approach. The obtained m-BN/PNF nanocomposite paper with 50 wt% m-BN presents excellent thermal conductivity, incredible electrical insulation, outstanding mechanical properties and thermal stability, due to the construction of extensive hydrogen bonds and π-π interactions between m-BN and PNF, and stable nacre-mimetic layered structures. Its λ_∥ and λ_⊥ are 9.68 and 0.84 W m^-1 K^-1, and the volume resistivity and breakdown strength are as high as 2.3 × 10¹⁵ Ω cm and 324.2 kV mm^-1, respectively. Besides, it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640 °C, showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.

Keywords: Boron nitride; Electrical insulation; Poly(p-phenylene-2,6-benzobisoxazole) nanofiber; Thermal conductivity.

Fig. 1

Schematic diagram of the preparation process for m-BN/PNF nanocomposite paper (a); optical photograph and SEM image of PBO fibers (b); the process of converting PNF solution into m-BN/PNF sol (c, c′); TEM images of PNF (d, d′); optical photographs of m-BN/PNF gel with certain flexibility (e, e″); SEM images showing the inside of m-BN/PNF gel (f, f′); schematic diagram of the interaction mechanism between PNF and m-BN (g); optical photographs of m-BN/PNF nanocomposite paper showing excellent flexibility and foldability (h, h″); cross-sectional SEM images of m-BN/PNF nanocomposite paper (i, i′)

Fig. 2

FTIR (a) and XRD (b) spectra of m-BN and BN; XPS wide-scan spectra (c) and high-resolution C 1s XPS spectra (d–f) of PNF paper, BN/PNF and m-BN/PNF nanocomposite paper

Fig. 3

λ_∥ (a) and λ_⊥ (b) of BN/PNF and m-BN/PNF nanocomposite paper at room temperature; the curves of temperatures vs. time (c) for heating resistor on air, PNF paper and m-BN/PNF-50 nanocomposite paper and corresponding infrared thermal images (c′); the curves of temperatures vs. time (d) for the bare lithium-ion rechargeable battery, the lithium-ion rechargeable battery integrated with PNF paper and m-BN/PNF-50 nanocomposite paper, and corresponding infrared thermal images (d′); TGA curves (e) of PNF paper and m-BN/PNF-50 nanocomposite paper; optical photographs of PNF paper (f) and m-BN/PNF-50 nanocomposite paper (g) before and during burning; SEM images of PNF paper (h) and m-BN/PNF-50 nanocomposite paper (i) after burning

Fig. 4

Cross-sectional SEM images (a, b) of m-BN/PNF-50 nanocomposite paper; schematic diagram of thermal conduction for m-BN/PNF-50 nanocomposite paper in the in-plane (a′) and through-plane (b′) direction

Fig. 5

ε (a) and tanδ (b) of m-BN/PNF nanocomposite paper at different frequencies; ε (c) and tanδ (d) of PNF paper and m-BN/PNF-50 nanocomposite paper in the range of − 50 to 200 °C; volume resistivity (e) of m-BN/PNF nanocomposite paper; Weibull plots for breakdown strength (f) of PNF paper and m-BN/PNF-50 nanocomposite paper

Fig. 6

Optical photographs of m-BN/PNF-50 nanocomposite paper possessing ultra-flexibility and withstanding a 1-kg reactor (a); tensile stress–strain curves of BN/PNF (b) and m-BN/PNF (c) nanocomposite paper; tensile strength (d), tensile modulus (e) and toughness (f) of BN/PNF and m-BN/PNF nanocomposite paper