Low density and high strength nanofibrillated cellulose aerogel for thermal insulation application

Abstract

Low density and high strength nanofibrillated cellulose aerogel based on pinewood were prepared by the freeze-drying method. The study was focused to reduce the thermal conductivity of the prepared aerogel along with the improvement in mechanical strength. Synthesized nanofibrillated cellulose aerogel had demonstrated high porosity (99.4%) and ultra low density (8.1 kg/m3). Morphological analysis of aerogel by FESEM (Field emission scanning electron microscope) confirmed nano-dimensional diameter of cellulosic fibres and pore size distribution of aerogel in the range of 2–50 nm. X-ray microtomography confirmed the three-dimensional, monolithic and porous structure. The mechanical and thermal transport properties of aerogel have been tailored via controlling the concentration of nanofibrillated cellulose in the hydrogel. The synthesized aerogel act as a thermal insulator with the thermal conductivity of 25.5 mW/m K at 1.00 wt% of aerogel, which is near to the thermal conductivity of air in ambient condition. Cyclic compression strength of aerogel was investigated at 25%, 50% and 75% strain for 50 cycles. 1.00 wt% aerogel was 70% recoverable at 25% strain but reflecting strain-hardening behaviour at 75% strain. 1.00–1.50 wt% aerogels have shown ductile, flexible and compressible behaviour. Nanofibrillated cellulose aerogel would be a candidate in practical applications such as heat insulator, kinetic energy absorber and energy efficiency building.