Rheology of Cellulose Fiber Disperse Systems and Cellulose Solutions

Abstract

The dynamic moduli of cellulose fiber disperse systems showed a strong dependence on fiber concentration. Power law relationships were established between the moduli and concentration. The exponent of the power law was 9/4 for all the suspensions constructed with three-dimensional isotropic fiber networks. In contrast, the exponent was three for wet pulp fiber webs, which have laminated fiber network structures, and five for a bacterial cellulose pellicle, having another laminated structure. This indicates that the exponent itself reflects the intrinsic properties of the fiber network structures. On the other hand, the front factor of the power law varied with the fiber axial ratio and the fiber flexibility. Therefore, the factor reflects the individual fiber characteristics. Solution properties of cellulose from different biological origins were also investigated in terms of rheological properties in LiCl/amide solutions. Bacterial cellulose solutions form liquid crystal phases, unlike the other celluloses solutions. Tunicate cellulose has large molecular weight as M_w = 4.13 × 10⁶. The solution viscosities were proportional to the α-th power of the polymer concentrations. The exponent α were 3, 4, and 7.5 for bacterial, plant, and tunicate cellulose solutions in the semi-dilute regions. The weight fraction dependence of the zero-shear rate viscosity of the blends can be expressed by a linear mixing relation based on Ninomiya theory.