Mechanical activation and characterization of micronized cellulose particles from pulp fiber

Ball milling has been widely used for cellulosic fiber pulverization and de-crystallization, but most of the previous milling studies are focused on the micro-structural change and crystallinity reduction of cellulose, few of them have evaluated the systematic influence of milling conditions and the energy efficiency. The objective of the study is to investigate and understand the effect of various ball milling parameters on the pulp fiber grinding performance. Ball mill time, rotational speed, charge ratio, mill ball diameters, and initial moisture content of pulp fiber were studied systematically from planetary ball milling. The pulverized particle size, particle morphology, crystallinity change, bonding disruption, thermal stability, specific surface area, and energy efficiency were evaluated during the milling process. Results revealed that cellulose fiber was mainly pulverized during the early milling stage (˜20 min) and different variables led to changes regarding to the final particle size and shape. After refinement, the crystallinity and the thermal stability of the pulp fiber decreased, from the weakening or disintegration of the inter and intra hydrogen bonds of the cellulose chains. The specific surface area increased by 4˜5 times with the particle size reduction, while the milling energy efficiency decreased after 40 min of milling time.