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ORIGINAL RESEARCH

Yield stress analysis of cellulose nanocrystalline gels Behzad Zakani . Dana Grecov

Received: 13 January 2020 / Accepted: 29 August 2020 Ó Springer Nature B.V. 2020

Abstract 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.

B. Zakani  D. Grecov (&) Department of Mechanical Engineering, University of British Columbia, Vancouver, BC, Canada e-mail: [email protected]

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Cellulose

Graphic abstract

Keywords Rheology  Yield stress  Cellulose nanocrystals

Introduction Cellulose nanocrystals (CNCs) are biodegradable, non-toxic and sustainable nanomaterials with a great potential for industrial applications (Grishkewich et al. 2017; Reid et al. 2017; Gicquel et al. 2019) due to their optical, electrical, thermal, tribological, rheological and several other intriguing properties (Araki et al. 1998; Shafiei-Sabet et al. 2012; Kelly et al. 2013; Hamad 2017; Shariatzadeh and Grecov 2019). These spindle-like nanoparticles are typically extracted from cellulosic biomass using strong acid hydrolysis (Shafiei-Sabet et al. 2012). Their shape, size and surface properties highly depend on the origin of biomass, the composition of the acid and hydrolysis conditions (Shafiei-Sabet et al. 2012; Hamad 2017; Gicquel et al. 2019). Due to their unique properties, CNCs are used in various fields with a wide range of

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applications (Grishkewich et al. 2017; Hamad 2017). In biomedical engineering CNCs are used for applications such as drug delivery (Akhlaghi et al. 2014), tissue engineering (Domingues et al. 2014) and biosensors (Dong and Roman 2007). In energy and electronics sectors, they have been employed for supercapacitors (Liew et al. 2013) and conductive films (Van Den Berg et al. 2007). There are also some current advancements in applications such as oil and gas industry (Kalashnikova et al. 2011; Li et al. 2015), as well as food sector (Vandamme et al.