Unified Scaling of Network Strength in Cellulose Nanofibrils from Dilute Suspensions to Dense Mats

Abstract

While the rheological properties of low-consistency cellulose nanofibril (CNF) suspensions and the mechanical properties of dry CNF films have been reported, research on high-consistency suspensions and wet CNF mats remains limited. Understanding suspension behavior during dewatering over a wide range of solids contents is essential. In this study, CNF consistency was controlled up to 20% using pressurized dewatering, and rheological behavior was characterized up to 10.2% solids content. Tensile testing was applied at higher concentrations where mat-like behavior emerged. The network strength followed a consistent power-law relationship across the entire solids content range, with a scaling exponent of 2.74, indicating that CNF flocculation is fundamentally similar to that of pulp fiber behavior despite its higher aspect ratio and smaller dimensions. CNF initiated network formation at a consistency more than twice as low as that of pulp fiber and exhibited a 5- to 20-fold higher network strength. At high solids contents, tensile strength increased exponentially, while elongation reached a maximum at approximately 50% solids content, suggesting a transition from capillary-driven consolidation to a hydrogen-bonded network. Nanofibrillation enhanced both tensile breaking stress and strain-at-break across all investigated solids contents. These results provide a framework for controlling CNF structural properties during dewatering and consolidation.