Methacrylate and polymer grafting pulp pretreatments reduce refining energy to produce modified cellulose nanofibrils.

Pretreatment of pulp is a critical step in the fibrillation process to improve the quality and efficiency for cellulose nanofibril (CNF) production. This work employed a straightforward and entirely aqueous methacrylation and subsequent grafting-through polymerization technique to modify bleached softwood kraft pulp (BSKP). Specifically, methacrylate groups, poly(acrylamide) (PAM), and poly(methyl methacrylate) (PMMA) were chemically affixed to the surface of BSKP fibers, which was confirmed using FTIR spectroscopy. Bench-scale experiments were scaled up to pilot scale to prepare the modified BSKP samples, these were subjected to fibrillation using a Supermasscolloider (SMC), and the net cumulative energy (NCE) expended was monitored during the fibrillation process. Notably, the modified BSKP samples exhibited a substantial reduction in NCE, with the methacrylate modified BSKP sample achieving a 68% reduction in NCE expenditure to attain 90% fines as compared to the fibrillation of unmodified BSKP and producing methacrylate modified cellulose nanofibrils (Met-CNFs). Furthermore, we delved into the impact of polymeric surface modifications, both pre-and post-fibrillation, on fiber and fibril behavior, including the water retention value (WRV), hard-to-remove water (HR-Water), and rheological behavior. The attached polymer's hydrophilicity and hydrophobicity influenced the physical properties of the CNFs. Additionally, we executed a post-grafting polymerization process on the produced Met-CNFs. This additional step allowed us to modify nanofibril surfaces, yielding increased surface functionalization and producing modified CNFs that could be used for composite applications. [ABSTRACT FROM AUTHOR]