Enhancement of cellulose nanofibril (CNF) film barrier properties by nanofibril alignment

Abstract

This study is centered on improving the mechanical and barrier characteristics of cellulose nanofibril films for food packaging applications. The goal was to induce fibril orientation, which was achieved by fabricating CNF films via an auto-dynamic sheet former (ADSF) at varying wire speeds, and varying CNF suspension solid contents. The wet-laid films were then dried using restrained (Z_Z shrinkage) and non-restrained (XY_Z) methods. Z_Z films demonstrated higher strength compared to XY_Z films at wire speeds of 1000 m/min and 1100 m/min. Films produced at 1100 m/min demonstrated the best oxygen barrier properties, irrespective of the drying technique employed. For 1100 m/min 0.1 wt.% films, the oxygen permeability values were decreased by 51.7% for the Z_Z shrinkage drying method and 40.3% for the XY_Z shrinkage drying method when compared to 900 m/min 0.1 wt.% films. The orientation of the film was assessed using polarized light microscopy (PLM) and wide-angle X-ray scattering (WAXS). However, these methods seemed to be limited to specific instances, as only a small area of the film could be imaged which did not provide a comprehensive indication of the overall alignment of the film, likely due to averaging of film’s response to these techniques caused by their multi-layer structure. Future research could delve deeper into producing oxygen barrier packaging materials using similar formulations in a paper-forming machine. Additionally, a potential future study could explore depositing an aligned CNF layer directly onto the paper substrate to form sustainable food containers made of paper.