(54b) Rheological Characterization of Nanocellulose Materials for Quality Control

Nanocellulose material is a renewable and sustainable nanomaterial produced from abundant cellulose sources. Its high strength and biodegradability make it attractive to many applications such as composites, coatings and rheological modifiers. Two types of nanocelluloses are mostly studied in the literature. One is cellulose nanocrystal (CNC), which are rod-like colloidal particles. The other is TEMPO oxidized cellulose nanofibril (TEMPO-CNF), which are flexible fibers. To ensure consistent production of high quality nanocellulose materials, one of the most urgent issues to be addressed is the lack of standardized, rapid and reliable characterization methods in the manufacturing environment. Electron microscopy and light scattering are two current characterization techniques. Nevertheless, the former is expensive and time-consuming, and the latter is extremely sensitive to aggregation. Moreover, both techniques only probe a small portion of the nanocellulose sample, which may misrepresent the sample’s bulk properties. Rheology provides a fast and cost-effective way to characterize nanocelluloses in large volume. In this work, we will show the potential of rheology as a quality control tool for nanocellulose materials. We developed detailed test protocols to obtain reliable viscosity data. We studied the influence of concentration on rheological properties of CNC and TEMPO-CNF, and formulated a rheological model to accurately capture the viscosity across shear rates and concentrations. We will demonstrate the model’s capability to determine the concentration of a nanocellulose sample by measuring the sample’s viscosity for both CNC and TEMPO-CNF. We will also show that the processing conditions, including the effect of pressure homogenization (pressure and number of passes) and the carboxylate content of TEMPO-CNF, can be identified through viscosity measurements. The measurement and the model can be applied on the industrial-grade viscometer and the capillary rheometer for quality control.