Gel structure phase behavior in micro nanofibrillated cellulose containing in situ precipitated calcium carbonate

Speciality high-strength board, packaging grades, and novel cellulose-based nanocomposites may incorporate microcellulosic nanofibrillated materials (MNFC), although the rheological properties of such strongly water sorbing structures are challenging for processing technologies. This study introduces rheological methods for the evaluation of dewatering and flow behavior of such high consistency furnishes to exemplify the effect of energy input on microfibrillar material (MFC), as produced by a combination of enzymatic pretreatment and increased levels of fluidization. The large number of fibril contact points act to entrap water, held both on the fibril surface as immobilized water and in the interfibril spacing forming the gel structure. Tuning of the rheological and dewatering properties has been enabled by in situ precipitation of calcium carbonate filler (in situ PCC) on the MFC, which results in the production of a more uniform furnish. Such in situ PCC coated MFC fibrils incorporated into furnish were seen to increase dewatering rate over that of the furnish mix without the in situ precipitated filler primarily because of the reduction in total surface area of the fibers and fibrils when the pigment is present on the fibrillary surface.