Effect of pH on water durability of cellulose nanofiber-reinforced starch film

Abstract The continuous use of single-use petrochemical-based plastics has created a global crisis with a significant buildup of plastic pollution. The use of biomass resources as a replacement source of plastic constituents, namely cellulose and starch, may contribute to alleviating the crisis. In this study, cellulose nanofiber-reinforced starch films were produced and studied for their pH response in terms of their swelling behavior and wet tensile strength in both freshwater and seawater conditions. Mechanically fibrillated cellulose nanofibers (MCNFs) were blended with dialdehyde starch (Di-aldS) and made into MCNF/Di-aldS films. The films were found to swell more and had a lower wet tensile strength at pH of 9. The film’s strength reduced to 1.60 MPa in basic conditions, 80% less than in acidic environment. This is related to hemiacetal crosslinking, resulted from the interactions between the modified moieties of the starches and cellulose nanofibers. Such bioplastics enhance the reusability of cellulose nanofibers and have the potential to replace conventional petrochemical plastics to create a carbon–neutral circular society. Graphical abstract