Rheological Properties of High-Consistency Enzymatically Fibrillated Cellulose Suspensions

Cellulose nanomaterials (CNMs) are promising renewable, bio-based and biodegradable materials, which have been explored for numerous applications in packaging, electronics, biotechnology, etc. These exciting applications have led to the development of various CNM production methods. However, challenges related to production costs still prevail and often the resulting material is at low consistency, typically between 1–5%, which limits logistics. If one up-concentrates the material to high consistency, the resulting high viscosity makes it difficult process the material further into products. To overcome these challenges, a high-consistency enzymatic fibrillation (HefCel) technology was developed at VTT, allowing nanocellulose production at 10%–25% consistency with significantly lower energy consumption compared to other manufacturing methods [1]. The material also possesses much lower viscosity than the other conventional grades of CNMs.
This work studies the rheological behavior of CNMs prepared using the HefCel technology. The effect of enzyme dosage and the raw material type on the CNM flow properties is explored. Three different bleached chemical pulps viz. never-dried softwood, once-dried softwood, and once-dried hardwood pulp were used along with three different enzyme dosage levels to each pulp type to produce nine different HefCel grades. All HefCel grades were characterized for their rheological behavior and the flow behavior was also compared to other conventional CNM grades (Figure 1). Moreover, morphology of the HefCel grades was correlated with their corresponding rheological behavior in order to determine a structure-property relationship.