Elucidating the Relationship Between Structure and Property of Waterborne Polyurethane-Cellulose Nanocrystals Nanocomposite Films

Cellulose nanocrystals (CNCs) are promising polymer reinforcements owning to their biocompatibility and high elastic modulus, low density, nano size, and inherent biocompatibility. The waterborne polyurethane-cellulose nanocrystals (WPU-CNCs) nanocomposite films were prepared using the conventional solvent casting technique over a whole composition. The mechanical performance, optical transmittance, amphiphilicity, water vapor permeability (WVP), and oxygen permeability (OP) of these WPU-CNCs films were evaluated. The incorporation of CNCs into WPU resulted in a significant enhancement of Young's modulus and tensile strength. The WVP of nanocomposite films had a lowest value at CNCs content of 50 wt.%. Upon the increase of CNCs content from 0 to 90 wt.%, the transmission path of oxygen molecular through the nanocomposite films became more tortuous, leading to drastic decrease in the OP. These WPU-CNCs nanocomposite films with high strength, optical transparency, water vapor and oxygen barrier properties have the potential applications in biomedical, furniture coating, and food packaging fields.