Use of Micro/Nano- and Nanofibrillated Cellulose To Improve the Mechanical Properties and Wet Performance of Xylan/Chitosan Films: A Comparison

Abstract

Growing health and environmental regulations are enforcing the preparation of sustainable and eco-friendly materials. In this context, this study investigates the effects of incorporating in a strategic manner micro/nanofibrillated cellulose (M/NFC) and only the nanofibrillated cellulose fraction (NFC) into xylan (Xyl)/chitosan (Ch)-based materials. The objective is to establish the bases to formulate films with optimized mechanical and wet performance. The M/NFC was successfully obtained from commercial spruce dissolving pulp by oxalic acid pretreatment followed by mechanical processing. The M/NFC and the NFC fraction were deeply characterized by complementary techniques. It was found that the nanofibrillation yield was 60% and the content of the carboxylic acid groups increased with the treatments (up to 267 μeq/g). To obtain homogeneous films, fibrillated cellulose was dispersed in the cationic polyelectrolyte solution (Ch) prior to the anionic polyelectrolyte (Xyl) addition. The films prepared with the cellulosic material up to 5-7 wt % of M/NFC or NFC were shown to be nonporous, uniform, and highly transparent (particularly when NFC was used). Furthermore, the crystallinity, thermal stability, and mechanical properties of the films increased, mainly when 5 wt % M/NFC was used (stress at break 88.6 MPa, strain at break 5.6%). The cellulose-containing films were less water-sensitive, kept their integrity after immersion in water, and showed an enhanced hydrophobicity surface compared to the reference Xyl/Ch film. All these results suggest that the addition of micro- and nanofibrillated cellulose under proper conditions is an alternative to improve the properties of natural-based films, highlighting their potential application for food packaging.