Morphological and structural development of hardwood cellulose during mechanochemical pretreatment in solid state through pan-milling
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Mechanochemical pretreatment of hardwood cellulose was conducted by our self-designed pan-mill equipment which has an unique and smart structure and can exert strong shear forces and pressure on materials in between and break them down. The structure transformations, including particle size, powder morphology, molecular structure, crystalline structure during milling were investigated by Laser Diffraction Particle Size Analyzer, SEM, FT-IR and WAXD, respectively. Compared with standard method of ball-milling, the pan-mill shows a much higher efficiency in mechanochemical pretreatment of hardwood cellulose. The average particle size reduced to 21 μm and the specific surface area increased to 0.8 m2/g after 40 milling cycles. Mechanical milling also led to collapse of hydrogen bonds and reduction of crystallinity. The crystallinity index of cellulose powder decreased from its original 65 to 22, after milling for 40 cycles. Thermal analysis and solubility testing illustrated that pan-milled cellulose has lower thermal stability and higher solubility in aqueous alkali.
KeywordsBall-milling Cellulose Crystallinity Mechanochemical Pan-milling Solubility Specific surface area Thermal degradation
The authors would like to thank NSAF Project (10476014) of the Joint Foundation of the Council of National Science Foundation of China-China Academy of Engineering Physics for financial support, and thank Analytical and Testing Center of Sichuan University for providing XRD and SEM measurement facility.
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