Rheological and Flocculation Analysis of Microfibrillated Cellulose Suspension Using Optical Coherence Tomography

Antti Koponen,Sanna Haavisto,Janne Lauri,Tapio Fabritius

doi:10.3390/app8050755

Antti Koponen, Sanna Haavisto + Show 2 more

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https://doi.org/10.3390/app8050755

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Abstract

A sub-micron resolution optical coherence tomography device was used together with a pipe rheometer to analyze the rheology and flocculation dynamics of a 0.5% microfibrillated cellulose (MFC) suspension. The bulk behavior of the MFC suspension showed typical shear thinning (power-law) behavior. This was reflected in a monotonously decreasing floc size when the shear stress exceeded the yield stress of the suspension. The quantitative viscous behavior of the MFC suspension changed abruptly at the wall shear stress of 10 Pa, which was reflected in a simultaneous abrupt drop of the floc size. The flocs were strongly elongated with low shear stresses. With the highest shear stresses, the flocs were almost spherical, indicating a good level of fluidization of the suspension.

Highlights

Microfibrillated cellulose (MFC) is a material of high interest due to its sustainability and biodegradability, and unique properties such as, mechanical robustness, barrier properties, large surface area, and lightness [1,2]
For the flow velocity profiles profilesobtained obtainedcould couldbebe characterized in the following way
Whenwhen the wall shear stress waswas below thethe yield stress τyτ=y 3.4

Summary

Introduction

Microfibrillated cellulose (MFC) is a material of high interest due to its sustainability and biodegradability, and unique properties such as, mechanical robustness, barrier properties, large surface area, and lightness [1,2]. There has been explosive growth in MFC research, including improved MFC production technologies, surface functionalization, characterization techniques, composites processing, self-assembly, optical properties, and barrier properties. The applications of MFC are already numerous including supercapacitors, transparent flexible electronics, batteries, barrier/separation membranes, and antimicrobial films [3]. A frequently noted issue in the processing of MFC suspensions is their complex rheological behavior. MFC suspensions tend to form a strong gel, which shows, for example, yield stress, shear thinning, hysteresis, and thixotropy already in low mass concentrations.

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