Production of nano-scale cellulose nanocrystal powder via electrospray drying (ESD) for sustainable composites

Abstract

This research introduces the use of electrospray drying (ESD) using the electro-hydro dynamic atomization (EHDA) mechanism to produce dry nano-scale cellulose nanocrystal (CNC) powder from a 3 wt% aqueous suspension. The nano-scale CNC suspensions being mostly water are energy intensive to dry. Gas atomization in convection spray drying (SD) produces micron-scale CNC powder during dehydration. The ESD mechanism utilizes coulomb repulsion to overcome the suspension’s liquid surface tension and produces ultra-fine droplets. The droplets dehydrate after falling a fixed distance at atmospheric temperature and pressure, leaving nano-scale powder CNCs. Drying CNCs in suspension occurred after reducing the liquid’s surface tension by mixing 40% (wt) ethanol and 60 (wt) de-ionized (DI) water. The suspension feed rate was optimized at 6 µL min−1 and four syringes were employed to increase CNC powder production rates. Particle dimensions, observed by scanning electron microscopy (SEM) and measured by image analysis software, ranged from 40 to 1200 nm in length and 10–500 nm in width. Up to 80% of the sprayed CNCs in suspension were recovered from a parallel plate collector and contained ~ 5 wt% water content. Adding 0.5 wt% nano-scale powder CNCs in the poly-lactic acid (PLA) tensile strength by 10.3% and elastic modulus by 9.9%. The tensile yield strength and elastic modulus of nano-scale CNC/PLA composite specimens were 62.5 MPa and 3.66 GPa, respectively. For comparison, 0.5 wt% SD micron scale CNC/PLA composite only increased strength 5.1 and stiffness 1.3% at the same processing conditions.Graphical abstract