Preparation Of Nanocellulose By Mechanochemical Processing And Its Modification

Nanocellulose has good performance and application in fine chemicals, medicine and material.Mechanochemical technology makes use of mechanical energy to cause chemical changes and physicalchemical changes, which is applied to preparation of ultra micro-crystals, nanocrystals andnanocomposites.In this paper, nanocellulose was prepared by mechanochemical processing using phosphoric acid as anassistant. one-factor experiments were done and the Box-behnken design in Design Expert software wasused to optimize reaction conditions. The optimal conditions are H3PO4concentration of81.64%, reactiontime of159.29min, reaction temperature of51.43℃, ultrasonic time of2.23h, the predicted value of yieldis92.24%, and the actual value is92.05%, showing the model is reasonable.Fiber morphology was observed by a Fiber Analyzer. The fiber of pulp was fine and some were short.The lengths and widths of pulp fibers were between0.68~5.31mm and15~60μm. The lengths and widthsof pulp fiber shortened under the mechanochemical effect. And microfibrils were generated and twistedinto an interconnected web-like structure. The rod-like nanocellulose fibers form an interconnectedweb-like structure. The lengths and widths of nanocellulose fibers were about between100~300nm and10~40nm. Microfibrils disperse into finer and shorter fibers without destruction of interconnected web-likestructure. Fourier Transform Infrared Spectrometry (FTIR) spectra show nanocellulose, cellulose colloidand pulp has basic structure of cellulose, showing the structure of cellulose didn’t change during thepreparation. X-ray Diffraction (XRD) results showed the crystal form of cellulose changed and thecrystallinity declined. The stability of nanocellulose was worse than that of pulp.Modified nanocellulose were prepared using urea, concentrated sulfuric acid, phosphoric/polyphosphoric acid as catalysts respectively and their properties were characterized. FTIR spectra showedthe effects of swelling time, amount of urea and reaction time on of urea-modified nanocellulose. Thepositions of characteristic peaks were almost consistent with that of nanocellulose except the peak at1724cm-1and the intensity of hydroxide group decreased with swelling time increasing. Much or a littleurea didn’t help to the production of cellulose ester. Reaction time of60min and90min help to product theester. The ester may hydrolyze at reaction time of120min. The effect of the dosage of concentrated sulfuric acid on FTIR spectra of sulfuric acid-modified nanocellulose was studied. The white colloidnanocellulose phosphate was prepared at concentration of75%and76%P2O5. The prepared nanocellulosephosphate was achromatic transparent colloid at concentration of77%P2O5.The ultrastructures of modified nanocellulose were observed. Urea-modified nanocellulose fiber wasrod-like and forms an interconnected web-like structure. The fibers widths were between20~50nm. Thefibers of sulfuric acid-modified nanocellulose were round and form arborizations. XRD results showedamorphous and crystal regions of urea-modified nanocellulose and nanocellulose phosphate weredestroyed. The sulfuric acid-modified nanocellulose was cellulose II crystals. The stabilities of modifiednanocellulose were worse than that of pulp.