0D-2D nanohybrids based on binary transitional metal oxide decorated boron nitride enabled epoxy resin efficient flame retardant coupled with enhanced thermal conductivity at ultra-low additions

Epoxy resin (EP) possesses standout traits in adhesion, electrical insulation, as well as mechanical properties, thus it is frequently concerned in the field of electronic packaging. However, EP has shortcomings of poor flame retardancy and thermal conductivity, and it is easy to induce thermal runaway in long-term service. In this work, 0D-2D nanohybrids (BN@CoFeOx) were obtained through a facile coprecipitation-thermal oxidation method, where cobalt-iron metal oxides as decorations were in situ generated on the surface of boron nitride (BN) as the substrate. Then, EP/BN@CoFeOx nanocomposites were prepared by physical blending of BN@CoFeOx and EP, pouring and curing. BN@CoFeOx nanohybrids fulfilled homogeneous dispersion in EP and strong interfacial interactions with the EP matrix. Besides, BN@CoFeOx nanohybrids imparted EP with high flame-retardant efficiency and exceeding smoke suppression properties at low additions of only 2 wt%, reflected in a 44.7%, 42.7%, 54.8%, and 56.2% decrease of the peak heat release rate (pHRR), total heat release rate (THR), peak smoke production rate (pSPR), and total smoke production (TSP) values, respectively. Furthermore, the limiting oxygen index (LOI) value increased from 24.2% of EP to 34.3%, and the vertical combustion test (UL-94) results reached a V0 rating. Meanwhile, the introduction of BN@CoFeOx nanohybrids adjusted for the formation of highly graphitized carbon layers, and boosted the thermal stability of EP. When the addition of BN@CoFeOx nanohybrids was 0.5 wt%, the peak mass loss rate (Rmax) of EP/BN@CoFeOx nanocomposites dropped by 33.6%. In addition, on account of the phonon transfer within and between nanohybrids, combined with the thermal conduction path formed by nanohybrids, BN@CoFeOx accomplished the thermal conductivity enhancement of EP. Hence, the newly designed and prepared EP/BN@CoFeOx nanocomposites provide the possibility to dissipate heat accumulation and promote the flame-retardant performance of electronic products, and consequently reduce the occurrence of thermal runaway.