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Open AccessArticle

Fumed and Precipitated Hydrophilic Silica Suspension Gels in Mineral Oil: Stability and Rheological Properties

Laboratory of Colloid Rheology, Division of Chemistry for Materials, Graduate School of Engineering, Mie University, 1577 Kurimamachiya, Tsu 514-8507, Japan
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Received: 26 June 2017 / Revised: 3 August 2017 / Accepted: 7 August 2017 / Published: 9 August 2017
(This article belongs to the Special Issue Rheology of Gels)
Hydrophilic fumed silica (FS) and precipitated silica (PS) powders were suspended in mineral oil; increasing the silica volume fraction (φ in the suspension led to the formation of sol, pre-gel, and gel states. Gelation took place at lower φ values in the FS than the PS suspension because of the lower silanol density on the FS surface. The shear stresses and dynamic moduli of the FS and PS suspensions were measured as a function of φ. Plots of the apparent shear viscosity against shear rate depended on φ and the silica powder. The FS suspensions in the gel state exhibited shear thinning, followed by a weak shear thickening or by constant viscosity with an increasing shear rate. In contrast, the PS suspensions in the gel state showed shear thinning, irrespective of φ. The dynamic moduli of the pre-gel and gel states were dependent on the surface silanol density: at a fixed φ, the storage modulus G′ in the linear viscoelasticity region was larger for the FS than for the PS suspension. Beyond the linear region, the G′ of the PS suspensions showed strain hardening and the loss modulus G″ of the FS and PS suspensions exhibited weak strain overshoot. View Full-Text
Keywords: fumed silica suspension; precipitated silica suspension; mineral oil; surface silanol density; stability; rheological properties fumed silica suspension; precipitated silica suspension; mineral oil; surface silanol density; stability; rheological properties
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MDPI and ACS Style

Sugino, Y.; Kawaguchi, M. Fumed and Precipitated Hydrophilic Silica Suspension Gels in Mineral Oil: Stability and Rheological Properties. Gels 2017, 3, 32.

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