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.

Graphic abstract

中文翻译：

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纤维素纳米晶凝胶的屈服应力分析

屈服应力是重要的流变性质，可用于确定材料在各种应用中的适用性。关于屈服点的定义及其测量技术尚无共识。因此，定义屈服点的唯一值将是至关重要的，但也是一项艰巨的任务。尽管已对纤维素纳米晶体（CNC）悬浮液的流变学进行了广泛研究，但对CNC凝胶的屈服行为却很少关注。在这项研究中，作者对高浓度CNC悬浮液进行了不同的流变测试，以研究其屈服行为。蠕变结果显示出清晰的粘度分叉及其相应的真实屈服应力。通过调整旋转和振荡流变仪的适当条件，可以获得静态和动态屈服点的可再现值。应力梯度流变仪被证明是确定静态和动态屈服应力的最合适方法。流变学结果还显示屈服点与CNC浓度成线性比例，并且存在屈服应力达到零的临界浓度。

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