Rheological characterization of microfibrillated cellulose suspension using optical coherence tomography

Haavisto, Sanna; Salmela, Juha; Jäsberg, Ari; Saarinen, Timo; Karppinen, Anni; Koponen, Antti

doi:10.32964/10.32964/tj14.5.291

Cited by 26 publications

(26 citation statements)

References 20 publications

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“…12a-f) and apparent slip flow (see Fig. 12a, b, g), the shear viscosity of CMNF suspensions is exceptionally difficult to measure quantitatively with good accuracy (Saarinen et al 2014;Haavisto et al 2015;Martoia et al 2015;Nazari et al 2016). Apparent slip flow may have influenced viscosity data considerably also when it is not apparent in the rheogram.…”

Section: Discussionmentioning

confidence: 99%

“…The use of Eq. (1), however, necessitates very accurate measurements, especially with small shear rates where, e.g., the effect of apparent slip flow on the geometry boundaries (Buscall, 2010;Saarinen et al 2014;Haavisto et al 2015;Martoia et al 2015;Nazari et al 2016) has been successfully eliminated. (Pääkkö et al 2007), and f TEMPO-oxidized CMNFs from eucalyptus (Honorato et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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The effect of consistency on the shear rheology of aqueous suspensions of cellulose micro- and nanofibrils: a review

Koponen

2019

Cellulose

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While the raw material type and the production method of cellulose micro- and nanofibrils (CMNFs) strongly affect the absolute values of the rheological parameters of their aqueous suspensions, the dependence of these parameters on consistency, c, is found to be uniform. The consistency index and yield stress of CMNF suspensions follow generally the scaling laws $$K \sim c^{2.43}$$K∼c2.43 and $$\tau_{y} \sim c^{2.26}$$τy∼c2.26, respectively, and a decent approximation for flow index is $$n = 0.30 \times c^{ - 0.43}$$n=0.30×c-0.43. The variability of reported scaling exponents of these materials is likely mainly due to experimental uncertainties and not so much due to fundamentally different rheology. It is suggested that the reason behind the apparently universal rheological behavior of CMNF suspensions is the strong entanglement of fibrils; the flow dynamics of typical CMNF suspensions is dominated by interactions between fibril flocs and not by interactions between individual fibrils. Graphic abstract

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effect of consistency on the shear rheology of aqueous suspensions of cellulose micro- and nanofibrils: a review

Koponen

2019

Cellulose

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“…Graphs of Eq 3 fitted to DOCT data are shown as dashed lines. The geometric interpretation of the fitting parameters is given in subfigure (a) (Haavisto et. al.…”

Section: Viscosity Characteristicsmentioning

confidence: 99%

Characterization of micro-fibrillated cellulose fiber suspension flow using multi scale velocity profile measurements

Kataja

Haavisto²,

Salmela³

et al. 2017

Nordic Pulp &Amp; Paper Research Journal

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Rheological properties and boundary layer flow behavior of Micro Fibrillated Cellulose (MFC) suspended in water was studied using a novel velocity profiling rheometric technique. The method is based on measuring stationary velocity profiles of fluid flow in a straight tube simultaneously by Doppler Optical Coherence Tomography (DOCT) and by Ultrasound Velocity Profiling (UVP). The high resolution DOCT provides velocity profiles near the transparent tube wall, while UVP yields corresponding information in the interior parts of the flow. The data from the two instruments is combined into a comprehensive velocity profile including both the thin boundary layer near the wall and the interior parts of the flow. Within the boundary layer, concentration and thereby the viscosity of MFC is found to decrease towards the wall. At high flow rate, sublayer of virtually pure water is observed next to the wall, giving rise to apparent wall slip. The results from interior part of the flow show shear thinning behavior in qualitative agreement with results from conventional rheological methods. The results indicate that the new method can provide detailed experimental information on the rheology of MFC suspensions and their intricate boundary layer flow behavior, avoiding uncertainties inherent in many conventional rheological techniques.

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“…MNFC suspensions have a high flocculation tendency, and they often exhibit strong apparent wall slip due to wall depletion close to solid walls. The width of the wall depletion layer can vary between a few micrometers and a few hundred micrometers, depending on the MNFC grade, MNFC consistency, and flow conditions (Haavisto et al 2015a;Lauri et al 2017;Kataja et al 2017). The slip flow makes it challenging to produce reliable information on shear rheology of MNFC using standard rotational rheometer geometries such as plate-plate, cone and plate, and cylinder cup geometries (Saarinen et al 2014;Martoia et al 2015;Vadodaria et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Pipe rheology of microfibrillated cellulose suspensions

Turpeinen

Jäsberg

Haavisto³

et al. 2019

Cellulose

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The shear rheology of two mechanically manufactured microfibrillated cellulose (MFC) suspensions was studied in a consistency range of 0.2-2.0% with a pipe rheometer combined with ultrasound velocity profiling. The MFC suspensions behaved at all consistencies as shear thinning power law fluids. Despite their significantly different particle size, the viscous behavior of the suspensions was quantitatively similar. For both suspensions, the dependence of yield stress and the consistency index on consistency was a power law with an exponent of 2.4, similar to some pulp suspensions. The dependence of flow index on consistency was also a power law, with an exponent of -0.36. The slip flow was very strong for both MFCs and contributed up to 95% to the flow rate. When wall shear stress exceeded two times the yield stress, slip flow caused drag reduction with consistencies higher than 0.8%. When inspecting the slip velocities of both suspensions as a function of wall shear stress scaled with the yield stress, a good data collapse was obtained. The observed similarities in the shear rheology of both the MFC suspensions and the similar behavior of some pulp fiber suspensions suggests that the shear rheology of MFC suspensions might be more universal than has previously been realized.

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Rheological characterization of microfibrillated cellulose suspension using optical coherence tomography

Cited by 26 publications

References 20 publications

The effect of consistency on the shear rheology of aqueous suspensions of cellulose micro- and nanofibrils: a review

The effect of consistency on the shear rheology of aqueous suspensions of cellulose micro- and nanofibrils: a review

Characterization of micro-fibrillated cellulose fiber suspension flow using multi scale velocity profile measurements

Pipe rheology of microfibrillated cellulose suspensions

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