Rheological properties of cellulose-chitosan-phosphoric acid systems in different phase states

Rheological properties of 7.0–9.1% cellulose-chitosan suspensions, solutions, and gels in aqueous phosphoric acid were examined in various modes of shear flow in the range 0.15–100 s −1 at 268–323 K. During steady state flow, the appearance of a quasi-Newtonian region was detected at shear rates between 20 and 40 s −1 owing to orientational ordering of macromolecules in the stream. Under the conditions of transient shear flow at a constant shear rate, rheopexy was observed in both cellulose solutions and cellulose-chitosan solutions. The thixotropic behavior of cellulose-chitosan suspensions, spinning solutions, and gels was characterized during a sharp drop of shear rate from 0.15 to 10 s −1 , that is, under conditions modeling the processes of transport and extrusion of spinning solutions.