Surface modification of cellulose nanofiber film with fatty acids for developing renewable hydrophobic food packaging

Cellulose Nanofibers (CNF) have been increasingly investigated as an alternative to plastic packages. Despite their excellent mechanical properties, their hydrophilic nature affects their application as a food packaging component. Chemical modification can improve their hydrophobicity, but result in films with the poor mechanical property. In this study, we investigated the modification of premade CNF films with saturated fatty acids lauric, palmitic, and stearic acids using modification techniques that aimed to preserve mechanical property while maintaining hydrophobicity. Two modification techniques were followed: bulk modification, where the entire film was exposed to the reaction medium and surface modification where only one of the surfaces of the CNF film was exposed. The resulting films were investigated for their proof of modification, mechanical and water vapor barrier property, surface free energy, crystallinity, and their thermal stability. Both modification techniques resulted in films with increased surface hydrophobicity; the films that were formed through bulk modification of CNF improved its water vapor barrier property significantly (p < 0.05). The surface modification technique, however, resulted in modified films that better preserved their mechanical properties. Hence, from this study, it can be concluded that it is possible to improve the hydrophobicity of CNF films without affecting their mechanical properties.