Production and Assessment of Cellulose Nanofibril Films

Abstract

This research was a study on the production and characterization of novel, high (i.e. above 80 wt.%) nanocellulose (CNF) content. These films were successfully created after an established CNF production process (Pascoli, Dichiara, Roumeli, Gustafson, & Bura, 2022) using alkaline pulping and a peracetic acid (PAA) pretreatment was scaled to a kilogram scale. The resulting CNF pulping yield was 68 %, and both chemical and morphological composition of the CNF was maintained from the translation from gram to kilogram scale production. The average CNF fiber diameter was 21.0 nm and the average length weighted was 0.89 mm; high levels of cellulose (100 %) and hemicellulose (92 %) were maintained, contributing to the optical and mechanical properties of the CNF. This CNF was then used in combination with polyvinyl alcohol (PVA) to create film composites at high CNF (i.e. above 80 wt.%) and low PVA (i.e. below 20 wt.%) ratios. These films had unexpectedly impressive optical properties with a maximum haze of 94.7 % in 100 % CNF films and a maximum light transmittance at 660 nm of 85.7 % at 660 nm in 85 % CNF films. This unique combination of high haze and high light transmittance lends the films to a variety of exciting applications. The composite films were also evaluated for mechanical properties, and 100 % CNF were found to have a high tensile strength of 86.3 MPa with a peak elongation of 4.2 %. These results indicated that the films retain flexibility associated with traditional plastic while benefiting from enhanced mechanical properties associated with CNF. Furthermore, the films were evaluated for mass retention when submerged in moist soil for eleven weeks and for susceptibility to water via contact angle analysis. It was found that the films did not immediately undergo decomposition and remained relatively stable in soil, and they exhibited a decreased susceptibility to water when compared to 100 % PVA control films. The outstanding properties of the film suggest potential applications in solar energy conversion devices, single-use food packaging, or agricultural mulch coverings.