Boron Nitride Nanotubes in Polycarbonate for Thermal Management Applications

Boron nitride nanotubes (BNNTs) are among the most effective additives for producing polymeric nanocomposites that exhibit high thermal conductivity but remain electrically nonconductive. However, the main challenge in the fabrication of such composites comes from the low dispersibility of BNNTs in polymeric matrices. This research aims to establish guidelines for controlling the morphology of nanocomposite, thereby adjusting their thermal conductivity and heat dissipation rate for optimized heat management applications. Two mixing methods, solvent and melt mixings, have been employed to incorporate noncovalently functionalized BNNTs (poly(3-hexyl-thiophene) (P3HT)-BNNTs) into a polycarbonate matrix, and the effects of processing conditions on the morphology of the nanocomposites have been decoupled and analyzed systematically. Smaller microscale agglomerations of BNNTs with better dispersion were observed with the melt mixing method, whereas the solvent mixing method maintained a higher aspect ratio of BNNTs. Although improved thermal conduction was evident, thermal conductivity in either mixing method did not change significantly up to 5 wt % BNNT; however, the heat dissipation rate of the melt-mixed samples was around twice higher. This indicates that the heat dissipation rate is sensitive to the morphology and length of the nanotubes in the samples. UV–vis-NIR spectroscopy and enhanced truncated-correlation photothermal coherence tomography (eTC-PCT) studies revealed that the higher heat dissipation rate of the melt-mixed samples is attributable to better dispersion and distribution of BNNTs that were enhanced by their smaller agglomeration sizes and aspect ratios.