A Simple Conversion of Holocellulose Fibers into a Potential Bioplastic

Abstract Lignin is one of the major obstacles to conferring thermoplastic properties on lignocellulosic material. The trifluoroacetic anhydride (TFAA) esterification method is applied to previously delignified banana and flax fibers. This solvent‐free, room‐temperature reaction modifies the structure of holocelluloses derived from natural fibers, giving them new intrinsic properties and potential as bioplastic alternatives superior to those obtained from non‐delignified fibers. Esterified flax holocelluloses showed slightly higher WPG as well as ester content (6.77 to 14.34 mmol/g) than esterified banana holocelluloses (7.99 to 11.73 mmol/g). Chemical analysis by FTIR and CP/MAS 13C NMR proves a successful esterification reaction through the disappearance of hydroxyl groups present in the non‐modified holocelluloses, replaced by ester groups and alkyl chains of fatty acids. A significant decrease in cellulose crystallinity results after esterification of holocelluloses, based on evaluations of certain intensities in the CP/MAS 13C NMR results. The hydrophilic holocelluloses, which appear fibrous and brittle and degrade irreversibly under the effect of heat, become hydrophobic, smooth, and flexible once pressed. Thermal analyses (TGA and DSC) show improved thermal stability once the fatty acids are grafted onto the holocelluloses, and softening temperatures are identified, confirming the thermoplastic nature of these new materials, which can thus be infinitely reshaped once heated and then cooled. These new intrinsic properties acquired by chemical modification of the fibers offer promising prospects for replacing petro‐sourced plastics with bio‐sourced materials.