Nanoporous Polybenzoxazine Aerogels for Thermally Insulating and Self-Extinguishing Materials in Aerospace Applications

Phenolic-based aerogel composites possess particular characteristics, such as low thermal conductivity, light weight, and superior ablative properties, in near-space vehicles. However, their machinability and flammability require further improvement, hampering their application for high-performance thermal protection systems in the aerospace field. Here, we prepare nanoporous polybenzoxazine (PBO) aerogels with outstanding thermally insulating and self-extinguishing properties by an effective-cost ambient pressure drying (APD) approach rather than a conventional high-pressure supercritical drying pattern. The PBO aerogels are prepared by adopting different exchange solvents of tert-butyl alcohol, ethanol, and n-hexane. The results obtained indicate that PBO aerogels (with n-hexane as the exchange solvent) by APD have an optimal three-dimensional nanoporous network structure, a pore size distribution in the range 20-140 nm, an obvious self-extinguishing property (extinguished itself instantly despite exposure to a 1200 degrees C flame), superior thermal insulation (the cold surface temperature of the sample reached only 36.4 degrees C after 400 s despite its opposite surface existing at a 65.8 degrees C atmosphere), and excellent machinable properties (easy-to-form special-shaped sample). PBO aerogels are a great potential candidate material system for thermal protection systems in aerospace applications in the future.

Automated summary

In this study, nanoporous polybenzoxazine (PBO) aerogels were successfully prepared with excellent thermal insulation and self-extinguishing properties using a simple ambient pressure drying method. The PBO aerogels exhibited superior self-extinguishing performance at high temperatures, maintained good thermal insulation, and were easy to process into various special-shaped samples.