Rheological behavior of cellulose/monohydrate of n-methylmorpholine n-oxide solutions. Part 1: Liquid state
Résumé
Steady-state and dynamic experiments have been performed on solutions containing cellulose dissolved in monohydrate of N-methylmorpholine N-oxide (NMMO). The dependence of the zero-shear viscosity η0, and of the terminal relaxation time τc, on concentration, average degree of polymerization (DP̄) and temperature are discussed. The behavior of this semi-rigid, polymolecular polymer in solution differs from that of flexible monodisperse ones. The slope of the plot of log (η0) versus, on the one hand, log (c) at fixed molecular weight (DP̄) = 600, and, on the other hand, log (DP̄) at fixed concentration (c = 5% w/w) are equal to 4.6 and 5 respectively, instead of 3.4 in the concentrated region. Experimental data for the shear modulus were fitted using the classical Doi-Edwards equation with a log normal distribution of relaxation time. This distribution is compared to the distribution of DP.