RHEOLOGY OF CONCENTRATED N-METHYLMORPHOLI NE-N-OXIDE CELLULOSE SOLUTIONS

Rheological characteristics of cellulose solutions in N-methylmorpholi ne-N-oxide were studied at 90-120 degrees C in a wide range of composi tions. The viscosity of solutions with concentrations c < 0.18 wt. fra ct. obeys the laws characteristic of the solutions of flexible-chain p olymers. It is shown that cellulose farms in solution a network of int ermolecular contacts with a density much higher than that known in the solutions of flexible-chain polymers. This, together with increased r igidity of the cellulose backbone, leads to higher values of the modul us of elasticity. The cellulose solutions studied exhibited considerab le broadening of the spectrum of relaxation times with increasing conc entration. Cellulose solutions with c > 0.18 wt. fractions showed a co nsiderable increase in the degree of structurization, which led to ano malous increase in the relaxation times, and the values of viscosity, activation energy for the viscous flow, and elastic moduli.