Viscosity measurements of dilute aqueous suspensions of cellulose nanocrystals using a rolling ball viscometer

Cellulose nanocrystals (NCC) are produced through acidic hydrolysis and mechanical disintegration of cellulose. Plans to produce NCC on an industrial scale point to the need for an efficient method to characterize its suspensions. Viscosity is a bulk property that could be used for this characterization since it accurately describes the suspension and the inherent properties of the nanocrystals. Our objective was to develop a convenient way to characterize diluted aqueous NCC suspensions without the need of complex instrumentation. The viscosity of dilute suspensions was measured with an automated rolling ball viscometer, which requires only a small amount of sample. The feasibility of the proposed procedure was confirmed by using dextran solutions as standards. The NCC suspensions were characterized by their intrinsic viscosity [eta], which is directly related to the hydrodynamic dimensions of the nanocrystals. The data obtained were analyzed using the equations established by Huggins and by Fedors. Fedors' approach gave more accurate results, leading to a value of 213 mL g(-1) for the intrinsic viscosity, [eta]. The non-Newtonian character of NCC suspensions at increasing concentrations was evaluated.