Preserving the Nano-Scale Morphology of Cellulose Nanofiber via Drying Under High Shear Conditions

Cellulose nanomaterials (CNMs) hold great promise as renewable, sustainable and highly functional materials in a host of applications. However, to date CNMs have not seen large-scale commercial use, primarily due to the difficulty in removing the water in which they are generated without inducing extensive hydrogen bond-driven aggregation and concomitant loss of nano-scale elements. Spray drying of CNM suspensions has been shown to produce micron scale monoliths. Freeze drying and supercritical drying with carbon dioxide have proven more effective at maintaining the nanostructure of CNMs, but are not readily scalable to high throughput, energy efficient production. Here we present a new drying technique that preserves the nano-morphology of CNMs via use of a high shear drying environment. Indeed 3wt% cellulose nanofiber hydrogel suspensions were dried via the use of two vortices of heated compressed air to a nano-fibrous powder with yields of greater than 60% wt%. Our results demonstrate that it is possible to dry CNMs while largely preserving the nano-scale morphology of the material simply by drying in a turbulent heated air stream. The technique lends itself to ready scale-up and we anticipate will enable use of these renewable and sustainable materials in high volume commercial applications.