Abstract
Cellulose nanocrystals (CNCs) have attracted significant interest in different industrial sectors. Many applications have been developed and more are being explored. Pre-treatment of the suspension plays a critical role for different applications. In this study, different pre-treatment methods, including homogenization, ultrasonication, and mixing with a magnetic stirrer were applied to a CNC suspension. After treatment, the rheological behaviors of the treated CNC suspensions were characterized using a rotational viscometer. The treated suspensions were then used to cast films for characterization by ultraviolet-visible (UV-Vis) and Fourier transform near-infrared spectroscopy (FT-NIR). All the CNC suspensions demonstrated a shear thinning phenomena. Homogenization or ultrasonication significantly decreased the suspension viscosity compared with the suspension mixed by a magnetic stirrer. The viscosity of CNC suspension changed with time after treatment and settlement of treated CNC suspensions in room conditions increased the viscosity dramatically with time. Different UV and visible light interferences were observed for the CNC films generated from suspensions treated by different methods. The degree of crystallinity of the CNC films evaluated by FT-NIR showed that the film from suspension treated by homogenization and ultrasonication has the highest degree of crystallinity. Pre-treatments of CNC suspension affected the suspension viscosities and formed film properties.
Highlights
The interest in renewable nanomaterial of cellulose nanocrystals (CNCs) has been growing significantly for the past several decades
The viscosity of the original CNC suspension (CNC_O) was measured and the primary readings of spindle torque kept changing during the measurement
In the researched shear rate range, the CNC suspensions treated by magnetic stirrer stirrer mixing, mixing,homogenization, homogenization,ultrasonication, ultrasonication,and andcombination combination homogeniofof homogenization and ultrasonication zation and ultrasonicationdemonstrated demonstratedshear shearthinning thinningphenomena phenomenawhich which were were fitted fitted by power law flow models
Summary
The interest in renewable nanomaterial of cellulose nanocrystals (CNCs) has been growing significantly for the past several decades. CNC is the fundamental building block in crystalline structure to form cellulose elementary fibrils (microfibrils/nanofibrils). The cellulose microfibril/nanofibril consists of an additional cellulose amorphous region and the amorphous region arranges alternatively with the crystalline region along the fiber axis [7,8]. Production of CNCs from woody biomass is typically performed through a strong acid hydrolysis of cellulose materials, digesting the amorphous region. In this process, the cellulose source, acid reactant, and hydrolysis parameter impact the surface chemistry and particle morphology of the separated CNC particles. A stable colloidal suspension of CNCs in water can be prepared and the presence of negatively charged sulfate half-ester groups on the CNC surface prompts a well-dispersion aqueous suspension of CNCs [6,9–11]
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