Rheological properties of an amorphous cellulose suspension

Amorphous cellulose was prepared by the dissolution of microcrystalline cellulose with phosphoric acid and subsequent regeneration in water. The rheological properties of the aqueous suspension as affected by the concentration of cellulose, ionic strength, pH and temperature were studied. Amorphous cellulose forms a three-dimensional (3D) network, which displays typical shear-thinning behavior with little thixotropic tendency, at concentrations above 0.71%. Its flow properties are similar to that of microfibrillated cellulose, as determined by a three-region (shear thinning – plateau or shear thickening – shear thinning) viscosity profile, in which ionic strength and pH have little influence. However, increasing the temperature causes a decrease in the viscosity in both low and high shear rate regions. A viscoelastic analysis confirms that the ionic strength and pH have no influence, but increasing the temperature decreases the storage modulus, which is explained by the weakening or disruption of intermolecular interactions at elevated temperatures.