| Cellulose as one of the natural renewable resources is abundant on Earth. Its basedindustrial products are used in all aspects of people’s life. Cellulose has many advantages. Thedevelopment and application of cellulose have far-reaching significance on human resourcecrisis and environmental problems. However, high crystallinity and hydrogen bondingbetween intermolecular and intramolecular make cellulose insoluble, difficult to melt, and noplasticity, which limit its wide application in industry. Cellulose has no plasticity since itsmelting point is significantly higher than decomposition temperature. The thermaldecomposition has occurred before melting. Therefore, the research on thermoplasticmodification of cellulose has been hot and difficult in this field. In recent years, ionic liquidsas highly efficient green solvents made a major breakthrough in terms of dissolving naturalpolysaccharide macromolecules, which provided a way for development and utilization ofrenewable resource and for the preparation of new functional polymer materials. In this thesis,we aimed at synthetizing some thermoplastic cellulose materials homogeneously withmicrocrystalline cellulose as raw material and ionic liquid as solvent. The main contentsinclude the following aspects:(1) Cellulose was dissolved in ionic liquid (BmimCl) and they were characterized byviscosity method, FT-IR, XRD and TG before and after the dissolution. The results showedthat when cellulose was regenerated, its crystal form was transfered from type I to II, and thedegree of crystallinity decreased with the extension of the dissolving time and temperature.When dissolving temperature was less than100℃and dissolving time was less than4h, thecellulose degraded mildly. Conversely, there was significant degradation. Thermal stability ofcellulose decreased and its surface morphology changed after regeneration from ionic liquid.(2) Cellulose benzotate (CB) was synthesized from MCC and benzoyl chloride byhomogenous modification of MCC in ionic liquid. CBs with different DS were obtained bycontrolling the amount of benzoyl chloride. CBs were characterized by FT-IR,13C-NMR,SEM and XRD. Thermal properties were tested by DSC and TG. The results showed that C-2,C-3and C-6hydroxyl group of MCC have different reactivity. The priority of theesterification was C6-OH>C2-OH>C3-OH. The modificated microcrystalline cellulose have a distinct glass transition temperature, and temperature gradually decreased from182.24℃（DS=0.83）to173.36℃(DS=2.56).Modified microcrystalline cellulose showed a goodthermoplastic character.(3) Cellulose graft copolymers were prepared using two different methods in ionic liquid.One method was making use of radical polymerization to synthetize MCC-g-PAA andMCC-g-PMMA homogeneously with acrylic acid and methyl methacrylate as monomer,ammonium persulfate and benzoyl peroxide as an initiator respectively. The other was makingthe use of TDI as a crosslinking agent to prepare MCC-g-PEG by connecting cellulose withpolyethylene glycol. Cellulose graft copolymers were characterized by FT-IR, XRD. TheirThermal properties were examined by DSC and TG. The results showed that MCC-g-PAAandMCC-g-PEG were prepared successfully in ionic liquid, while MCC-g-PMMA failed to get.Cellulose graft copolymers showed thermal behavior obviously, wherein the glass transitionof MCC-g-PAAappeared at about188℃, showing certain thermoplastic. |
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