Abstract

Lignocellulose nanofibrils (LCNFs) are nano-objects that contain lignin. The presence of lignin in the fibrils affects the process production of cellulose nanofibrils. It modifies the morphology of fibrils produced and the rheological behavior of suspensions, which is crucial in developing applications for this material. This work aims to understand the role of lignin in the mechanical-enzymatic production process of LCNFs and the morphological, superficial, and rheological properties of LCNF suspensions. Lignin has a negative effect on the mechanical and enzymatic processes, generating larger fibrils with less homogeneous size distributions and with lower zeta potential. In addition, the composition of the fibrils changes, part of the lignin is removed and dispersed into the solvent in the form of lignin nanoparticles. These nanoparticles are neutral and can be deposited on the surface of the fibrils. Regarding rheological properties, fibrils with lignin are less flexible than bleached fibrils. Such characteristics are due to the cementing capacity of lignin, which increases the hydrodynamic volume that these structures occupy per unit mass. Furthermore, in the semi-dilute region, lignin acts as a control agent for the viscosity in the suspensions due to its hydrophobic characteristic, which forms weak aggregates, poorly hydrated, and hydrodynamically smaller, which generate less resistance to flow.