Yield stress analysis of cellulose nanocrystalline gels

The yield stress is an important rheological property which can be used to identify the suitability of a material for a wide range of applications. There is no consensus on the definition of the yield point nor on its measurement technique. Thus, defining a unique value for yield point would be crucial but a challenging task. Although rheology of Cellulose Nanocrystalline (CNC) suspensions has been widely studied, less attention has been paid to the yielding behavior of CNC gels. In this study, the authors performed different rheological tests on highly concentrated CNC suspensions to investigate their yielding behavior. Creep results demonstrated a clear viscosity bifurcation and its corresponding true yield stress. Reproducible values for static and dynamic yield points were obtained by adjusting the appropriate conditions for rotational and oscillatory rheometries. Stress ramp rheometry was demonstrated as the most proper method for determining the static and dynamic yield stress. Rheometry results also revealed that the yield points scale linearly with CNC concentration and there exists a critical concentration where yield stress reaches to zero. [GRAPHICS] .