Thermally insulating polybenzoxazine aerogels based on 4,4′-diamino-diphenylmethane benzoxazine

In situ co‐polymerization of high‐performance polybenzoxazine/silica aerogels for flame‐retardancy and thermal insulation

“…The characteristic peaks at 284.32, 399.54, 532.57, and 104.13 eV correspond to C 1s, N 1s, O 1s, and Si 2p from PBO/SiO 2 ‐2 aerogel. As can be seen from Figure 3(c), N 1s survey exhibits two peaks at 399.98eV, and 401.49 eV belongs to C‐N and C‐N···H, indicating the formation of hydrogen bond in PBO aerogel 17,47–48 . In contrast, only one peak at 399.54 eV belongs to C‐N in PBO/SiO 2 aerogels, which is in proper line with the peak of 3429 cm ‐1 is more evident in PBO aerogels than that in PBO/SiO 2 aerogels from FT‐IR spectra.…”

“…It is synthesized through ring‐opening polymerization of benzoxazine monomer under high temperature or acid catalyst and further forming a cross‐linked three‐dimensional network structure 12–16 . In the previous study, PBO aerogels were prepared with lightweight, low thermal conductivity, 17–18 and excellent mechanical strength, 18–19 a preliminary demonstration of its potential application performance in the field of thermal insulation. Besides, PBO resin possesses self‐extinguishment and intrinsic flame retardancy because of they contain Nitrogen element and lots of Phenol rings 20–21 .…”

Room Temperature Oxalic Acid‐Catalyzed, Ambient Pressure Dried, and Cost‐Effective Synthesis of Polybenzoxazine Aerogels for Thermal Insulation

“…In general, the PBZ aerogels exhibited an excellent thermally insulating property with thermal conductivity in a range of 0.0323-0.0619 W m À1 K under atmospheric pressure, which was far below that of PBZ aerogels based on Bisphenol A monomer reported in the literature (density 0.109 g cm À3 and conductivity 0.071 W m À1 K À1 ), [19] and even lower than that of the PBZ aerogels derived from PH-mda monomer ring-opening polymerization catalyzed by HCl and supercritical dried (0.035-0.057 W m À1 K À1 ), [21] this may be due to the weaker acidity of OA than HCl, and the longer time in ring-opening polymerization of PH-mda monomer for gelling, resulting in a finer microstructure and lower thermal conductivity of PBZ aerogels in this article but the exact reason still needs further exploration or accurate calculation. The thermal conductivity of 0.0119-0.0317 W m À1 K À1 at 10 Pa was dominated by solid heat transfer due to few gas molecules in the system, indicating that PBZ aerogels have an extremely low solid thermal conductivity, which is very beneficial for thermal insulation under a less atmosphere or a vacuum environment.…”

“…[38,44] About other absorption, the peak at 1115 cm À1 is attributed to C─N stretching of the Mannich bridge, and it is noted that it becomes extremely weak in PBZ aerogels. [19] The weak absorption at 812 cm À1 and strong absorption at 752 and 692 cm À1 are attributed to the out-of-plane C─H bending of the aromatic ring and dangling aniline of the PH-mda monomer, [18,19,21] and these peaks also become weak in PBZ aerogels. Considering the aforementioned together, we derived the structure of the formed PBZ aerogels as shown in Figure 1.…”

“…[17,18] Mahadik-Khanolkar [19] and Malakooti [20] reported that PBZ aerogels possess excellent mechanical properties and relatively low thermal conductivity. Feng [21,22] synthesized lighter PBZ aerogels with lower thermal conductivity and systematically studied their thermal conductivity. Moreover, PBZ resins possess many prominent advantages including intrinsic flame retardancy, eco-friendly synthesis process (without small-molecule release), and abundant raw materials.…”