Doctor of Philosophy (PhD)
School of Renewable Natural Resources
Transparent cellulose films from 2,2,6,6-tetramethylpiperidine-1-oxyl radical oxidized cellulose nanocrystals (TOCNs) and 64 wt% sulfuric acid treated cellulose nanocrystals (SACNs) were prepared from bleached wood pulps. Film morphology, optical, mechanical, thermal, and surface wettability properties were characterized and compared. The results showed that TOCNs and SACNs had different average length, diameter, and aspect ratio.
The effect of cellulose nanofibers (CNFs) on flow, hydration, morphology, and strength of oil well cement (OWC) was investigated using a range of spectroscopic methods coupled with rheological modeling and strength analysis. The Vom-Berg model showed the best fitting result of the rheology data. The addition of CNFs increased the yield stress of OWC slurry and degree of hydration value of hydrated CNF-OWC composites. The flexural strength of hydrated OWC samples was increased by 20.7% at the CNF/OWC ratio of 0.04 wt%. Excessive addition of CNFs into OWC matrix had a detrimental effect on the mechanical properties of hydrated CNF-OWC composites. Similar results were obtained for CNFs/graphene nano-platelets (GNPs) reinforced OWC, except that both flexural and compressive strengths of the CNF/GNP-OWC composites were enhanced.
Cellulose nanocrystals (CNCs) and CNFs were prepared and used to prepare 25 μm thick CNF/CNC films. Rheological behavior of CNF/CNC suspensions and the other relevant properties of the films were characterized in comparison with a commercial Polymer Battery Separator (PBS) film. The morphology analysis showed that CNFs and CNCs exhibited different film forming mechanism. The characterization results indicated that the CNF/CNC suspension zeta potential, film tensile strength, crystallinity index, and optical transparency were increased with the addition of CNCs in hybrid nanocellulose material. The CNF/CNC suspension viscosity and film porosity, thermal stability, and thermal expansion were increased with the increased CNF loading. The CNF/CNC films exhibited better thermal stability, thermal expansion behavior, and optical properties than those of commercial PBS film. The CNF/CNC films had more uniform strength along all directions whereas PBS film demonstrated anisotropic property. The wetting-envelope-based OWRK model can be used to predict the wetting behavior of different solvents on the manufactured films. This work paves a new strategy to tailor the properties of nanocellulose based films.
Sun, Xiuxuan, "Preparation and Characterization of Nanocellulose and Its Application in Composite Materials" (2018). LSU Doctoral Dissertations. 4199.
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