Effect of ultrasonic treatment on yield stress of highly concentrated cellulose nano-crystalline (CNC) aqueous suspensions

The yield stress of highly concentrated cellulose nano-crystalline (CNC) suspensions is an important rheological property for different applications. The ultrasonic treatment is a common technique for dispersing CNCs in aqueous media. Although the effect of ultrasonic processing on rheology of CNC suspensions has been previously investigated, a systematic approach studying the sonication effect on yield stress is missing in the literature. In this study, we investigated the effect of sonication energy within the energy level of 0-5000 J/gCNC on static, dynamic and true yield points of a highly concentrated (8 wt%) aqueous CNC suspension, through a rheo-optics analysis. To better understand the yielding behaviour, the sonication effect on physicochemical properties of the CNCs was also investigated. The results revealed that yield stress decreases with sonication energy through a four-step mechanism governed by the microstructural transformations of the CNC agglomerates.