Coupled Chemical and Ball Milling Pretreatments of Fluff Pulp for Enhanced Cellulose Nanofibril Production

The increasing demand for cellulose nanofibrils (CNF) necessitates the development of novel processes to produce high‐solid content and consistent product quality. In this study, a combination of ball milling and chemical pretreatments (carboxymethylcellulose (CMC) dispersion, and sodium hydroxide (NaOH) swelling) of fluff pulp followed by high‐pressure homogenization was investigated to produce CNF. The carboxymethylcellulose dispersion with 75 min ball milling and NaOH swelling with 15‐, 45‐, and 75‐min ball milling reduces the fiber dimensions by up to 90% and fibrillate with up to 6% solid content CNF during high‐pressure homogenization. The average fibril width was less than 30 nm, with good dispersion stability. The CMC dispersion and NaOH swelling with ball milling did not significantly affect the chemical structure and the crystallinity of CNF hydrogels. The tensile strength of all CNF samples was up to 105 ± 14 MPa more than the control sample (58 ± 6 MPa). NaOH treatment has slightly increased the thermal stability of CNF samples over CMC‐treated and control samples. In conclusion, short fibers generated by mild alkaline pretreatment with ball milling followed by high‐pressure homogenization of cellulose fibers produced consistent quality CNF with high solid content and increased tensile strength for packaging and coating applications.