Preparations and Thermal Properties of PDMS-AlN-Al2O3 Composites through the Incorporation of Poly(Catechol-Amine)-Modified Boron Nitride Nanotubes

Abstract

As one of the emerging nanomaterials, boron nitride nanotubes (BNNTs) provide promising opportunities for diverse applications due to their unique properties, such as high thermal conductivity, immense inertness, and high-temperature durability, while the instability of BNNTs due to their high surface induces agglomerates susceptible to the loss of their advantages. Therefore, the proper functionalization of BNNTs is crucial to highlight their fundamental characteristics. Herein, a simplistic low-cost approach of BNNT surface modification through catechol-polyamine (CAPA) interfacial polymerization is postulated to improve its dispersibility on the polymeric matrix. The modified BNNT was assimilated as a filler additive with AlN/Al₂O₃ filling materials in a PDMS polymeric matrix to prepare a thermal interface material (TIM). The resulting composite exhibits a heightened isotropic thermal conductivity of 8.10 W/mK, which is a ~47.27% increase compared to pristine composite 5.50 W/mK, and this can be ascribed to the improved BNNT dispersion forming interconnected phonon pathways and the thermal interface resistance reduction due to its augmented compatibility with the polymeric matrix. Moreover, the fabricated composite manifests a fire resistance improvement of ~10% in LOI relative to the neat composite sample, which can be correlated to the thermal stability shift in the TGA and DTA data. An enhancement in thermal permanence is stipulated due to a melting point (Tm) shift of ∼38.5 °C upon the integration of BNNT-CAPA. This improvement can be associated with the good distribution and adhesion of BNNT-CAPA in the polymeric matrix, integrated with its inherent thermal stability, good charring capability, and free radical scavenging effect due to the presence of CAPA on its surface. This study offers new insights into BNNT utilization and its corresponding incorporation into the polymeric matrix, which provides a prospective direction in the preparation of multifunctional materials for electric devices.

Keywords: boron nitride nanotubes; composites; fire retardant; polydimethylsiloxane; thermal conductivity; thermal interface materials.

Figure 1

(a) Schematic representation of the preparation of BNNT-CAPA and (b) SEM image of PDMS/AlN/Al₂O₃/BNNT-CAPA composite.

Figure 2

(a) FTIR spectra of CA, PA, BNNT-neat and BNNT-CAPA. (b,c) TGA and Zeta potential of BNNT-neat and BNNT-CAPA. (d–f) TEM image and (g) elemental line scan of BNNT-CAPA.

Figure 3

XPS survey of the surface-modified BNNT. (a) B 1s; (b) N 1s; (c) C 1s; (d) O 1s; (e) high resolution spectra.

Figure 4

(a,b) Photograph and schematic representation of BNNT-neat and BNNT-CAPA dispersed in the solvent resin mixture and its corresponding (c) isotropic thermal conductivity of neat, AlN/Al₂O₃, AlN/Al₂O₃/BNNT-neat, and AlN/Al₂O₃/BNNT-CAPA. (d) Heat dissipation mechanism of the functionalized and non-functionalized BNNT incorporated composite and its corresponding phonon conduction pathways.

Figure 5

(a–h) Thermal evolution simulation during heat flux dissipation in the PDMS, PDMS/AlN/Al₂O₃, PDMS/AlN/Al₂O₃/BNNT and PDMS/AlN/Al₂O₃/BNNT-CAPA composite.

Figure 6

(a) Heating and (b) cooling profiles of neat and BNNT incorporated samples and (c,d) their corresponding thermal infrared images (the concentration of all the samples is 87% wt).

Figure 7

Flammability characteristic investigation using (a) LOI, (b) TGA, (c) differential thermal analysis (DTA) curves and (d) DSC and (e) the flame-retarding mechanism of BNNT-incorporated composite.

Figure 8

(a) Radical reactions between CAPA and regular free radicals (ROO* and HOO*). (b) Flame retardant of prepared composites.