High Solids Fibrillation of Cellulosic Fibers with and without Pretreatments through Planetary Ball Milling

This study conducted a detailed evaluation of the feasibility of producing microfibrillated cellulose (MFC) from a kraft bleached hardwood pulp at high solids loadings with and without pretreatments. MFCs produced by planetary ball milling at solids loading at 17% and 28% were compared with those from 1% and 5% under the same milling conditions. Fiber pretreatments using a commercial endoglucanase and mechanical refining using a laboratory PFI mill were also applied before ball milling at solids loading of 28%. Two mechanisms of fiber fibrillation were identified from the results obtained: (i) ball and fiber/fibril interactions and (ii) inter-fiber/fibril frictional and tensional interactions. High solids loading with both mechanisms (i) and (ii) enhanced fiber fibrillation. A higher solids loading tends to result in a more uniformly fibrillated MFC than that from a lower solids loading run. Endoglucanase pretreatment substantially shortened fibers to result in a pulverized-like MFC with short fibrils at extended milling time. Mechanical refining of fibers facilitated fibrillation to result in MFCs with a morphology similar to that from fibers without any pretreatment but for a much shorter ball milling time. The insights gained through this study provides relevant information with commercial significance about MFC production at high solids, not available in the literature.