Ammonium persulfate oxidized nanofibrillated cellulose as a sustainable wet-end paper reinforcement additive

Nanocellulose fibers (NFCs) with specific characteristics were synthesized using the economically attractive ammonium persulfate (APS) mediated oxidation process to evaluate their potential as wet end additives in paper. The surface charge and morphology of as-synthesized NFC were tailored and characterized, and the barrier and strength properties of NFC-reinforced papers were thoroughly examined as a function of NFC contents and characteristics. The addition of two different cationic polyelectrolytes promoted electrostatic bridging between pulp fibers and maintained NFC retention above 93% regardless of the NFC nature. Results demonstrate that the presence of NFC with lower surface charge yields papers with denser fibrous network, reduced air permeability, and higher specific tensile strength. Higher surface charge NFC, on the other hand, increased floc formation and decreased NFC retention likely due to reduced dispersion and NFC agglomeration with the dual component retention system. Significantly, APS-oxidized NFC may be generally applicable as a competitive alternative to expensive and/or environmentally taxing chemicals typically employed in the manufacturing of a variety of papers and boards.