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Quantifying the dispersion quality of partially aggregated colloidal dispersions by high frequency rheology

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Abstract

An important parameter for the performance of nanomaterials is the degree by which the nanoparticles are dispersed in a matrix. Optical microscopy or scattering methods are useful to characterise the state of dispersion, but are not generally applicable to all materials. Electron microscopy methods are laborious in preparation and typically offer only quantitative information on a very local scale. In the present work we investigate how high frequency rheological measurements can be used for partially dispersed suspensions at intermediate to higher particle loadings, even for high viscous matrices. Although the contribution of the particles is particularly visible in the low frequency linear viscoelastic behaviour, a more direct relationship between rheological properties and degree of dispersion can be derived from the loss modulus in the high frequency limit. To this end, a home-built piezo shear rheometer is constructed to extend the frequency range typically accessible by commercial rotational rheometers. Measurements on spherical silica particles, with a varying degree of dispersion in low molecular weight PDMS, are used to demonstrate how high frequency rheometry can be used to quantify dispersion quality. The linear viscoelastic properties are compared to analytical scaling theories to demonstrate that a hydrodynamically dominated regime is reached. The dependence of the relative high frequency loss modulus on volume fraction is then compared to predictions of a hydrodynamic viscosity model for the derivation of a dispersion quality index. It is used to follow the evolution of the dispersion quality as a function of mixing time and consumed power.

Graphical abstract: Quantifying the dispersion quality of partially aggregated colloidal dispersions by high frequency rheology

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Publication details

The article was received on 22 Aug 2017, accepted on 02 Oct 2017 and first published on 04 Oct 2017


Article type: Paper
DOI: 10.1039/C7SM01690E
Citation: Soft Matter, 2017, Advance Article
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    Quantifying the dispersion quality of partially aggregated colloidal dispersions by high frequency rheology

    B. Schroyen, J. W. Swan, P. Van Puyvelde and J. Vermant, Soft Matter, 2017, Advance Article , DOI: 10.1039/C7SM01690E

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