Synthesis and characterization of carboxymethylcelluloses from non-wood pulps II.: Rheological behavior of CMC in aqueous solution

This paper concerns the rheological behavior of carboxymethylcelulloses (CMC) derived after one and two successive steps from different non- wood bleached cellulose pulps. CMC rheological characterization was achieved in 0.1M NaCl solution, as a function of polymer concentration. The evidence of a critical concentration (C* < 1 g/ L) is discussed from steady shear and dynamic experiments. Rheological properties of the CMC were found to depend on the cellulose source reactivity and on their degree of substitution (DS). Higher molecular weight of initial cellulose was accompanied by higher apparent intrinsic viscosity of the CMC produced. Depending on the CMC concentration and on the degree of etherification, the system behaves as a solution or as a gel. In the case of abaca CMC sample, it is shown that after only one step of chemical modification and above a polymer concentration of 20 g/ L, the system behaves as a gel. The gel behavior was studied as a function of temperature. In the temperature range from 25 to 45°C, the rheological behavior was found to remain almost constant due to the existence of dispersed swollen aggregates. This unusual characteristic represents an advantage for applications such as oil recovery in the petroleum industry, where viscosity of the recovered fluid should not diminish with temperature.