Eco-friendly thermally insulating cellulose aerogels with exceptional flame retardancy, mechanical property and thermal stability

Eco-friendly thermally insulating cellulose aerogels made from environmentally friendly resources are very attractive in materials chemistry, but the high flammability limits their application. Herein, a novel phosphorus-containing flame retardant modifying agent (DOPO-IA) was incorporated into the cellulose nanofiber aerogel and the cellulose composite aerogels were prepared by esterification and followed by a freeze-drying process. The thermal conductivity of the resultant cellulose composite aerogels was in the range of 28.6–31.2 mW/(mK). Meanwhile, the cellulose aerogels modified with DOPO-IA showed significantly enhanced thermal stability, mechanical property, and flame retardant performance compared with the pure cellulose aerogel. The CNF-DI-3 showed a high char residue (19.8 wt%) at 700 °C, which was 187% higher than CNF. Specifically, CNF-DI-3 exhibited remarkable reductions in its PHRR and THR values which were 67% and 60%, respectively, as compared to those of CNF. In summary, it is of significance to synthesize mechanically robust and flame-retardant cellulose aerogels.