High flame-retardant and thermal insulation performances of sodium-alginate/chitosan aerogel by coating montmorillonite on pore surface

To explore high-performance thermal insulation materials for green buildings, the sodium-alginate/chitosan (AC) biomass aerogel was firstly prepared, which has a potential advantage of low thermal conductivity and also low price. Then, the montmorillonite (MMT) was further coated on the pore surface of the AC aerogel to improve its poor flame-retardancy performances. This new aerogel is called ACMMT. Finally, the flame-retardant, mechanical and thermal insulation performances of ACMMT aerogels were analyzed. Results turn out that: The limiting oxygen index of ACMMT with a MMT content of 70 wt% (ACMMT-70 %) is increased by 205 % times compared to that of the AC aerogel, and the mass-loss rate of ACMMT-70 % is only about 13.8 %. This enhanced flame-retardant performance of ACMMT can be explained by the MMT isolation layer formed on the pore surface of AC aerogel, hindering the spread of oxygen and heat, thus restricting the spread of flames. The mechanical performance of ACMMT aerogel is also improved, because of the hydrogen bond formed between MMT and AC, which can better support the skeleton structure. The thermal conductivity of ACMMT-70 % aerogel is about 0.0384 W m −1  K −1 , much lower than that of most existing commercial materials. Importantly, when the ACMMT-70 % aerogel is heated by a 100 °C heat source, the upper surface of the ACMMT-70 % aerogel could maintain a temperature of 37 °C for a long time, showing excellent thermal insulation performance.