Doctor of Philosophy (PhD)
Renewable Natural Resources
Cellulose fibers (Cellulose I, cellulose II and cellulose I/II Hybrid fibers) were successfully extracted from energycane bagasse by using a combined NaOH and NaClO2 treatment. After the delignification process, most lignin and hemicellulose were removed with a 27.4wt% yield of cellulose fibers, and the mean diameter of cellulose fibers decreased from 137±46 (raw fiber bundles) to 12±5μm (unpacked fibers). The raw bagasse fibers showed a three-step pyrolysis process, while isolated cellulose fibers had a one-step pyrolysis process. NaClO2 treatment caused the reduction of cellulose thermal stability due to its acting on lignin and cellulose. With 10h NaOH treatment, the ribbon shaped cellulose I fibers were converted to cellulose I/II Hybrid fibers with rougher surfaces. The percentage of cellulose I decreased from 100% to 5%, and the corresponding CI values increased from 58.2% to 68.8% during the conversion from cellulose I to II. After further NaClO2 treatment, the CI values were decreased because of partial destruction of hydrogen bond network. XRD, NMR and FTIR results present the same trend in the degree of crystallization for all the samples. Core-shell structured hydrogels consisting of a flexible interpenetrating polymer network (IPN) core and a rigid semi-interpenetrating polymer network (SIPN) shell were prepared through chemical crosslinking of polyvinyl alcohol (PVA) and sodium alginate (SA) with Ca2+ and glutaraldehyde. Cellulose nanoparticles (CNPs) with cellulose I and I/II structures extracted from energycane bagasse were incorporated in the hydrogels and their effects on hydrogels properties were investigated. The shell was micro-porous and the core was macro-porous, the translucent hydrogels had a water content of ~93 wt%. The hydrogels could be used in multiple adsorption–desorption cycles for dyes and the maximum methyl blue adsorption capacity increased 10% after incorporating CNPs. The homogeneous distribution of CNPs in PVA-SA polymer matrix, allowed additional hydrogen bonds among the polymer molecular chains, resulting in enhanced density, viscoelasticity, and mechanical strength for the hydrogel. With incorporation cellulose nanofiber I, the storage modulus of the IPN core and compressive strength of the hydrogel reached 600 Pa and 79.5kPa, respectively, 13 and 3.2 times higher than values for neat hydrogel, respectively. The core/shell structure, with a high ductility core and high strength shell, gave a hydrogel with improved performance, broadening potential applications.
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Yue, Yiying, "Cellulose Nanofibers from Energycane Bagasse and Their Applications in Core-Shell Structured Hydrogels" (2015). LSU Doctoral Dissertations. 1742.