Impact of physico-chemical properties of nanocellulose on rheology of aqueous suspensions and its utility in multiple fields: A review

Nanocellulose (NC), due to its sustainable nature, high aspect ratio, superior mechanical strength, and availability of functionalizable -OH groups, has been widely utilized as reinforcement in numerous fluids/plastics. The physico-chemical properties of NC, like surface characteristics, dimensions/aspect ratio and their concentration, significantly impact the interparticle interactions, such as the extent of hydrogen bonding, van der Waal forces, hydrophobicity, electrostatic attraction/repulsion, and cellulose entanglement, and have been found to play a critical role in regulating the overall rheological characteristics of fluids. The functionalized NC aqueous suspension exhibited unique shear thinning properties, thixotropic behavior, and quick steady-state viscosity recovery and viscoelastic properties. However, upon adding functionalized NC to other fluids, a different impact was noticed. For instance, it improved the viscosity, G ' and mechanical stability of bio-ink; the setting time and mechanical strength of cementitious fluids; increased the filtration performance and provided a unique thermo-thickening impact in case of water-based drilling-fluid; enhanced viscosity with time and heat in case of oil recovery, and so forth. Keeping in view the notable dependence of the rheology of fluids on NC additives, in the present review article, the impact of various physico-chemical properties of NC additives on the rheological behavior of NC aqueous suspension and its utility as a rheology modifier in multiple advanced fields has been explored. This review article, compared to previous studies, warrants an update on the impact of recent NC surface functionalization/blending techniques employed and NC aspect ratio on specific properties of multiple advanced fluids.