Processing and functional assessment of anisotropic cellulose nanofibril/Alolt/sodium silicate: based aerogels as flame retardant thermal insulators

This work concerns freeze-dry processing of CNF aerogels, including aluminum hydroxide trihidrate (Alolt) particles and Sodium silicate, as active and passive flame retardants, respectively. Alkalinity of Sodium silicate promotes stability, dissociation and co-precipitation of Al(OH)(3) component onto CNFs. The (auto)fluorescence-enabled confocal microscopy enabled visualization of anisotropic microstructure with open and closed-cell segments, depicting the Alolt as single and aggregated particles. Low thermal conduction ( 0.045 W/mK) was estimated, irrespective of composition, while Alolt was found to reduce (by 30%) the aerogel moisture content. Sodium silicate promotes char formation as passive action, reducing the evolution of gaseous species, while burning test shows complete flame retardation through active endothermic reaction assigned to Alolt. Additive combinations did not amplify, nor diminish, the flame retardant effect of particular component, yet affected positively the elastic modulus. Considering simple green processing, low additive load, and high insulation and flame retardant efficiency, these aerogels hold promise as thermal insulation materials. [GRAPHICS] .