Rheology of Mechano-Enzymatically Fibrillated Cellulose in Fiber Suspensions and Foams

Cellulosic materials are increasingly explored as renewable building blocks for applications such as packaging, insulation, and construction. Conventional production of microfibrillated cellulose (MFC) is energy intensive and results in suspensions with strong gel-like behavior even at low solids contents.1-3 High-consistency mechano-enzymatic fibrillation of cellulose (HC MFC, previously referred as HefCel) has emerged as a lower-energy alternative, enabling the production of MFC directly at high solid contents.2, 4 In this work, the rheological behavior of HC MFC is investigated over a range of concentrations in both fiber suspensions and fiber foams. Two grades of HC MFC, coarse and fine, are studied to elucidate the effects of fiber content and fibrillation degree on viscoelastic and flow properties. Commercial MFC is used as a reference material to benchmark the behavior of HC MFC against established systems. The results show that HC MFC suspensions and foams exhibit a predominantly elastic response at small deformations over the entire range of fiber consistencies studied (2.5-15 wt% for suspensions, 2.5-7.5 wt% for foams). Rheological properties depend systematically on fiber content and fibrillation degree, reflecting differences in fiber network strength. Compared with commercial MFC, HC MFC shows much lower stiffness and therefore improved processability at high fiber consistencies. These findings support the potential of HC MFC in the production of sustainable, low-density fiber-based materials.