Yielding and flow of cellulose microfibril dispersions in the presence of a charged polymer.
The shear flow of microfibrillated cellulose dispersions is still not wholly understood as a consequence of their multi-length-scale heterogeneity. We added carboxymethyl cellulose, a charged polymer, that makes cellulose microfibril dispersions more homogeneous at the submicron and macro scales. We then compared the yielding and flow behavior of these dispersions to that of typical thixotropic yield-stress fluids. Despite the apparent homogeneity of the dispersions, their flow velocity profiles in cone-plate geometry, as measured by rheo-MRI velocimetry, differ strongly from those observed for typical thixotropic model systems: the viscosity across the gap is not uniform, despite a flat stress field across the gap. We describe these velocity profiles with a nonlocal model, and attribute the non-locality to persistent micron-scale structural heterogeneity.
Laboratory of Biophysics, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands. john.vanduynhoven@wur.nl and TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Daan W
DW
de Kort
Unilever R&D, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands.
Sandra J
SJ
Veen
Laboratory of Biophysics, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands. john.vanduynhoven@wur.nl and TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Henk
H
Van As
Van der Waals-Zeeman Institute, IoP, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Daniel
D
Bonn
Unilever R&D, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands and Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands.
Krassimir P
KP
Velikov
Laboratory of Biophysics, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands. john.vanduynhoven@wur.nl and TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands and Unilever R&D, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands.
John P M
JP
van Duynhoven