Polysaccharides Based Random and Unidirectional Aerogels for Thermal and Mechanical Stability

Owing to the increasing energy demands and the environmental constraints, the need for bio-based materials has been on the rise due to their variety of favorable properties like biocompatibility, cost-effectiveness, large specific surface area, high porosity, and non-toxicity. Thermal stability and mechanical strength of aerogels are highly dependent on their micro-porous structures. A three-dimensional structure based on cellulose nanofiber/chitosan ( CNF/CS) aerogels was built using two different freezing methodologies, namely random freezing, and unidirectional freezing techniques, by changing mold shapes. The unidirectional aerogels ultimately resulted in high-temperature stability and mechanical strength. The results show that the unidirectional CNF/CS( u-CNF/CS) aerogels contain controlled micro porous orientation relative to random-CNF/CS ( r-CNF/CS) aerogels with the disordered porous distribution. The high-temperature stability with an increase of glass transition temperature Tg from 275 ℃( CNF ) to 283 ℃ ( CNF/CS ) , the ultra-low thermal conductivity of 0. 030 W/( m · K ) , and mechanical robustness of u-CNF/CS aerogels make them quite favorable for practical applications.