Fractionation Of Lignocellulose And Synthesis Of Cellulose-based Materials

Lignocellulose feedstock is a kind of abundant and renewable natural rescources, whichhas promising future in the production of environmentally friendly materiels, alternativeenergy and green chemicals. In this work, a green fractionation process of lignocellulose wasfirstly designed and the influence of ionic liquid pretreatment on the structure of fractionatedproducts was discussed. Then a variety of cellulose-based materials with high performancewere synthesized, such as hydrogels and films. Physical proterties, thermo-stability, surfacemorphologies and chemical properties of these cellulose-based materials were determined tofind the optimum additives and synthesis methods. The main contents of this work are shownas below.(1) AmimCl dissolution and regeneration were used as pretreatment to fractionatebamboo powder, followed by consecutively extraction with0.5M NaOH aqueous solutionand70%ethanol aqueous solution with1.0M NaOH. It was shown that relatively pure lignin(containing2.19-3.83%polysaccharides), hemicellulose, and cellulose (containing92.02-93.88%glucose) fractions were successfully obtained from this process. The chemicalstructures of these fractions were determined by NMR. The lignin fractions were shown asS-G-H type, and the hemicellulose fractions mainly consisted of4-O-methyl-glucuronicacid-arabino-xylan. AmimCl pretreatment was confirmed to slightly degrade the lignin andhemicellulose, partially cleave the side-chains of hemicellulose and decrease the total yield offractionation.(2) After a range of pretreatments, such as freeze-drying, ball-milling, mercerization anddissolution/regeneration, cellulose nanocrystals (CNCs) with different crystalline propertiesand morphologies were obtained from pretreated cellulose by hydrolysis or TEMPO oxidation.It was found that sphere-like CNCs were more likely to be obtained from cellulose materialswith high accessibility that were pretreated by mercerization or dissolution/regeneration. Forregenerated cellulose, oxidized CNCs had higher degree of crystallinity, higher yield andmore uniform size distribution than hydrolyzed CNCs. Therefore, TEMPO oxidation wasbetter method to prepare CNCs from regenerated cellulose.(3) CNCs, which were pre-grafted by polymerizable groups on surfaces, were used tosynthesize high elastic PAM hydrogels by free radical polymerization. CNCs acted as not onlyfillers but also crosslink agents in CNCs crosslinked hydrogels. In this work, the relationsbetween surface properties of CNCs and the performance of hydrogels were discussed indetail. It was shown that after TEMPO oxidation, the dispersibility of CNCs improved significantly in hydrogels, increasing the efficiency of CNCs reinforcement. Hydrogels thatwere reinforced by CNCs with longer side chain on their surfaces, had more efficient energydissipation system and better network mobility, which could give better stretching propertiesand higher water swelling abilities to hydrogels. The results illustrated that the synthesis ofCNCs crosslinked hydrogels with tunable perfomance were possible by changing the surfaceproperties of CNCs.4> Epoxidized soybean oil (ESO) was firstly used as a novel plasticizer to preparebiomass-derived ethyl cellulose films. Results showed that ESO was an effective plasticizerfor ethyl cellulose films that outstripped conventional plasticizers, i.e. dibutyl phthalate andtriethyl citrate. The ESO plastized films had preferable mechanical properties, lower vaporpermeabilities and better thermal stability, as well as non-flammability. The outstandingperformance showed its potential applications in food, packaging and medication, especiallywhen the concentration of ESO was15-25%in plasticized films. In the second step, theaddition of crosslinking agents, heat treatment, thermocompression and UV treatment wereused as post-treatments in order to sythsize ESO plasticized films with better performance.The thermocompression in relatively low temperature significantly improved the mechanicalporperties of plasticized films, and thus the thermocompressed films were more suitable fordurable packaging materials. Besides, the addition of5%ethylenediamine could enhance thestretching porperties and water blocking property of plasticized films, but decrease theirfolding endurance, making the films more suitable for special materials that required highwater blocking property.