Iron-Containing Polyhedral Oligomeric Silsesquioxane Assembly Supported on Hexagonal Boron Nitride and Its Effect on Epoxy Resins

Boron nitride (BN) has great potential to improve the thermal conductivity of polymers, and polyhedral oligomeric silsesquioxane (POSS) revealed the ability to prepare polymers with a low dielectric constant. Combining the two abovementioned materials, an iron-containing polyhedral oligomeric silsesquioxane assembly supported on hexagonal boron nitride (FePOSS@hbno) was prepared via two steps involving hydroxylation and self-aggregation. The morphology of nanohybrid FePOSS@hbno indicated that FePOSS successfully aggregated on the surfaces and edges, which was evidenced by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images. The nanohybrid was also confirmed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The well-characterized FePOSS@hbno was incorporated into epoxy resins, and the thermal conductivity of epoxy composites increased by 104.3% with 20 wt % FePOSS@hbno. The dielectric constant of epoxy composites containing 3.6 wt % FePOSS@hbno clearly decreased in the frequency range of 10³-10⁶Hz. Significantly, 3.6 wt % FePOSS@hbno reduced the peak of the heat release rate by 49.3% and increased the LOI value to 31.2%. Moreover, the condensed and gaseous phases were investigated in detail. The enhanced flame retardancy originated from the nanohybrid structure as well as the elemental merits.