Nanocellulose-based foam morphological, mechanical and thermal properties in relation to hydrogel precursor structure...

Foams were prepared from nanocellulose-based hydrogel precursors using a freeze-drying process. The work mainly aims at investigating the relationships between the mechanical and thermal properties of foams and the rheological properties of their hydrogel precursors, which were characterized in a previous paper. The structure of foams was characterized by SEM and confocal microscopy, their elasticity by compression tests, and their thermal conductivity by hot strip as well as transient pulsed techniques. A strong correlation was shown between the elastic properties of foams and those of their hydrogel precursors, and a minimum thermal conductivity was shown to appear at a cellulose volume fraction corresponding to a transition in viscoelastic properties of hydrogels. Results suggest that foams and hydrogels share common microstructural features, which makes it possible to tune the mechanical and thermal properties of foams by tuning the rheological properties of their hydrogel precursors.