Analysis of rheology and wall depletion of microfibrillated cellulose suspension using optical coherence tomography
|Author:||Lauri, Janne1; Koponen, Antti2; Haavisto, Sanna3,4;|
1Optoelectronics and Measurement Techniques Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, P.O. Box 4500, FI-90014 Oulu, Finland
2VTT Technical Research Centre of Finland Ltd, P.O. Box 1603, FI-40101 Jyväskylä, Finland
3Department of Physics, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland
4Spinnova Ltd., Asematie 11, 40800 Vaajakoski, Finland
|Online Access:||PDF Full Text (PDF, 7.4 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe201902266276
|Publish Date:|| 2018-09-13
A rheometric method based on velocity profiling by optical coherence tomography (OCT) was used in the analysis of rheological and boundary layer flow properties of a 0.5% microfibrillated cellulose (MFC) suspension. The suspension showed typical shear thinning behaviour of MFC in the interior part of the tube, but the measured shear viscosities followed interestingly two successive power laws with an identical flow index (exponent) and a different consistency index. This kind of viscous behaviour, which has not been reported earlier for MFC, is likely related to a sudden structural change of the suspension. The near-wall flow showed existence of a slip layer of 2–12 μm thickness depending on the flow rate. Both the velocity profile measurement and the amplitude data obtained with OCT indicated that the slip layer was related to a concentration gradient appearing near the tube wall. Close to the wall the fluid appeared nearly Newtonian with high shear rates, and the viscosity approached almost that of pure water with decreasing distance from the wall. The flow rates given by a simple model that included the measured yield stress, viscous behavior, and slip behavior, was found to give the measured flow rates with a good accuracy.
|Pages:||4715 - 4728|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
114 Physical sciences
Academy of Finland (project Rheological Properties of Complex Fluids) is gratefully acknowledged for supporting this work. We also want to thank senior research technician Ulla Salonen for the photograph of the MFC fibers (Fig. 1), and senior scientist Panu Lahtinen for preparing the MFC.
© Springer Science+Business Media B.V. 2017. This is a post-peer-review, pre-copyedit version of an article published in Cellulose. The final authenticated version is available online at: https://doi.org/10.1007/s10570-017-1493-5.