Triple-crosslinked network engineering of cellulose aerogels for intrinsically ultrahigh flame retardancy and thermal shielding

Abstract

Background Developing environmentally friendly cellulose aerogels with excellent flame retardancy and thermal protection remains challenging because of the inherent flammability of biomass and insufficient structural stability under high temperature conditions. Methods In this work, cellulose derived from Sphagnum moss was used as a scaffold with a three dimensional structure. Phytic acid (PA), chitosan (CS), and kaolin were incorporated through a crosslinking strategy combined with freeze drying. The porous network was stabilized by electrostatic interactions, extensive hydrogen bonding, and covalent crosslinking mediated by glutaraldehyde, resulting in a triple crosslinked architecture. The resulting PA-IM-SC was a lightweight aerogel based on cellulose with integrated flame retardant and thermal protection functions. Significant findings PA-IM-SC exhibited a limiting oxygen index (LOI) of 90 % and achieved a UL-94 V-0 rating. After exposure to a 1300 °C flame for 20 min, the backside temperature remained at only 186.5 °C. Cone calorimetry showed a peak heat release rate (PHRR) of 5.23 kW/m 2 and a total heat release (THR) of 1.28 MJ/m 2 . These improvements were primarily attributed to catalytic charring induced by PA and reinforcement of the protective char barrier by kaolin. This work demonstrates a network engineering strategy for developing lightweight and sustainable cellulose aerogels with ultrahigh flame retardancy and effective thermal protection from renewable biomass resources.