Thermal-insulating, flame-retardant and mechanically resistant aerogel based on bio-inspired tubular cellulose

Inspired by the tubular structures found in naturally occurring thermal-insulating materials, tubular cellulose aerogels with improved mechanical resistant, thermal-insulating and flame-retardant properties were prepared from kapok fibers via a facile process. In contrast to fragileness of traditional organic-inorganic composites, an optimized sample exhibited an ultra-high compressive strength of 32 MPa. The tubular structure of this material resulted in a 37.4 °C increase in heat preservation compared with that obtained from a pulp aerogel without this morphology. The H3PO4 decomposed from (NH4)2HPO4 in the formulation crosslinked the outermost cellulose fibers to generate a clay-reinforced dense carbon layer in conjunction with montmorillonite, which restricted the movement of flames and the outflow of volatile compounds. The gaseous voids of internal tubular fibers interrupted the heat transport pathways to inhibit thermal transmission and trapped combustible volatiles to reduce the penetration pressure experienced by the dense carbon layer greatly. The combined effects of the carbon layer and tubular structure effectively limited the transfer of heat, oxygen and volatiles, leading to non-combustion of the optimal sample. This study provided a cost-effective and facile approach to prepare of thermal-insulating, fire-safe and high-strength aerogel showing promising applications in exterior wall insulation and vehicle interior.