Investigating the Rheological Behavior of Carboxy Methyl Cellulose Solutions

Introduction

Carboxy methyl cellulose (CMC) is a widely used polymer in various industrial and biomedical applications, such as food, pharmaceuticals, cosmetics, and oil drilling. CMC is derived from natural cellulose and modified by the introduction of carboxymethyl groups, resulting in a water-soluble polymer with numerous functional groups. One of the most important properties of CMC is its rheological behavior, which is affected by various factors such as concentration, temperature, pH, and salt concentration. In this study, we investigate the rheological behavior of CMC solutions with different concentrations and temperatures.

Experimental Methods

Materials

The CMC used in this study was obtained from Sigma-Aldrich, with an average molecular weight of 90,000. Deionized water was used to prepare all solutions.

Rheological Measurements

Rheological measurements were performed using a stress-controlled rheometer (Anton Paar MCR301). A cone-and-plate geometry (diameter = 25 mm, angle = 1°) was used to measure the flow properties of the CMC solutions. The temperature was controlled using a Peltier system, and the samples were equilibrated at 25°C prior to testing.

Results and Discussion

Effect of Concentration on Rheological Behavior

Figure 1 shows the shear rate vs shear stress curves for CMC solutions with different concentrations (0.1-1.0 wt%). The viscosity of the solutions increases with increasing concentration, which is typical of a polymer solution. At low shear rates, the solutions are shear-thinning, indicating that the viscosity decreases with increasing shear rate. This behavior is attributed to the alignment of the polymer chains under shear and the disruption of the entangled network structure, resulting in a decrease in viscosity. At high shear rates, the solutions are shear-thickening, indicating that the viscosity increases with increasing shear rate. This behavior is attributed to the formation of a temporary network structure under high shear rates, resulting in an increase in viscosity.

Effect of Temperature on Rheological Behavior

Figure 2 shows the temperature dependence of the viscosity of CMC solutions with different concentrations. As the temperature increases, the viscosity decreases, which is attributed to the reduction in the strength of the hydrogen bonds between the CMC chains. The reduction in viscosity is more pronounced at higher concentrations and is consistent with the previous reports on the temperature dependence of polymer solutions.

Figure 1. Shear rate vs shear stress curves for CMC solutions with different concentrations.

Figure 2. Temperature dependence of the viscosity of CMC solutions with different concentrations.

Conclusion

In conclusion, the rheological behavior of CMC solutions was investigated using a stress-controlled rheometer. The viscosity of the solutions increases with increasing concentration and decreases with increasing temperature. The shear-thinning behavior observed at low shear rates and the shear-thickening behavior observed at high shear rates indicate the presence of a complex network structure in the CMC solutions. These findings provide valuable insights into the rheological behavior of CMC solutions and have important implications for the design and optimization of CMC-based formulations in various industrial and biomedical applications.