Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 539251
Title Nonlinear shear and dilatational rheology of viscoelastic interfacial layers of cellulose nanocrystals
Author(s) Berg, Merel van den; Kuster, Simon; Windhab, E.J.; Sagis, L.M.C.; Fischer, P.
Source Physics of Fluids 30 (2018)7. - ISSN 1070-6631 - 11 p.
DOI https://doi.org/10.1063/1.5035334
Department(s) VLAG
Physics and Physical Chemistry of Foods
Publication type Refereed Article in a scientific journal
Publication year 2018
Keyword(s) compressibility - contact angle - Hydrophobicity - nanomechanics - nanoparticles - polymers - Rheology - softening - viscoelasticity - work hardening
Abstract We present a nonlinear rheological investigation of model rod-like particles at the air/water interface in dilatation and shear. Cellulose nanocrystals were modified to vary their surface hydrophobicity, creating a range of surface-active particles with varying contact angle. The interfacial rheological properties were studied using a series of frequency sweeps in small amplitude oscillatory shear as well as strain sweeps under large amplitude oscillatory shear (LAOS) and large amplitude oscillatory dilatation (LAOD) to include the nonlinear behavior. A multi-mode Maxwell model was used to fit the frequency sweeps that were obtained during formation of the interfacial layer. A shift toward longer
relaxation times was found, more pronounced for particles with higher hydrophobicity. Lissajous plots in LAOS revealed strain stiffening, yielding, and unconstrained flow of the interfacial layers.
Lissajous plots in LAOD revealed strain hardening in compression and strain softening in expansion, increasing with surface pressure and with particle hydrophobicity. While interfacial layers commonly show gel or solid-like behavior, our findings imply a weakly aggregated system. The rheological
behavior indicates the formation of larger clusters for particles with high hydrophobicity compared to smaller clusters for particles with low hydrophobicity. The particle-particle interactions therefore vary with hydrophobicity, suggesting that capillary interactions are important for the formation of these microstructures.
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