Fabrication of Cellulose Nanofiber Aerogels by Freeze-Drying Using Water as Dispersion Medium

Abstract

This study describes a method to produce cellulose aerogels by freezing nanofiber aqueous suspensions and sublimating the water phase to obtain a lightweight porous structure. As the formation of water crystallites is highly dependent on the freezing speed, various methods were attempted to obtain homogeneously distributed microscopic pores in order to preserve the macroscopic mechanical integrity of the aerogel, i.e., a structure free of big size pores or cracks. The interconnection among the nanofibers is accomplished solely by hydrogen bonds. The scanning electron microscopy revealed the structural similarities with bacterial cellulose, an interconnected web-like network of nanofibers. Open cell structure aerogels were completely impregnated with epoxy resin using a vacuum assisted resin transfer molding (VARTM) to fabricate composites. The present protocol to obtain aerogels relies only on water, without the use of any chemicals, thus being an environmentally friendly process.