1993
DOI: 10.1122/1.550378
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Dynamic rheological behavior of flocculated fumed silica suspensions

Abstract: Fumed silica suspensions in low molecular weight solvents are used in many photonic and microelectronic applications. The rheology of these thixotropic systems plays a major role in the effectiveness of their usage. In this study, we use dynamic rheological measurements to examine the particle–particle and particle–solvent interactions of fumed silica with hydrophilic and hydrophobic surface groups dispersed in both polar and nonpolar solvents, polypropylene glycol and mineral oil, respectively. We find the mi… Show more

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Cited by 155 publications
(126 citation statements)
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“…Both silicas have approximately the same surface area (150 m2/g). The R805 silica-silica interactions in a liquid medium may involve both the hydrogen bonding interactions of silanols and also secondary dispersive interactions between the alkyl chains (Khan and Zoeller, 1993). Due to the decreased surface silanol density, the degree of network connectivity in a nonpolar medium is generally lower with R805 than with a corresponding hydrophilic silica of similar surface area.…”
Section: Experiment: Materials and Methodsmentioning
confidence: 99%
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“…Both silicas have approximately the same surface area (150 m2/g). The R805 silica-silica interactions in a liquid medium may involve both the hydrogen bonding interactions of silanols and also secondary dispersive interactions between the alkyl chains (Khan and Zoeller, 1993). Due to the decreased surface silanol density, the degree of network connectivity in a nonpolar medium is generally lower with R805 than with a corresponding hydrophilic silica of similar surface area.…”
Section: Experiment: Materials and Methodsmentioning
confidence: 99%
“…When dispersed in liquids, adjacent aggregates can interact via silanol-silanol hydrogen bonding, giving rise to larger structures called floes. At high silica concentrations a three- dimensional network of floes extends throughout the volume of the sample and the suspension is considered to be a "physical gel" (Kosinski and Caruthers, 1985;Khan and Zoeller, 1993). The flocculated microstructure thus has multiple levels: The aggregates can be regarded as the primary structure of the silica, the floes are made up of interconnected aggregates, and the network is composed of floes.…”
Section: Introductionmentioning
confidence: 99%
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“…The degree of network formation by fumed silica in a liquid depends on the concentration of solid and type (hydrophilic versus hydrophobic) of silica, as well as the nature (polarity) of the suspending medium. Therefore, these three main factors allow to the suspensions of Aerosil R fumed silica inside a fluid possess a variety of rheological behaviors (Khan & Zoeller, 1993;Raghavan & Khan, 1995). This variety of rheological behaviors makes silica particle a very interesting filler from the point of view of a wide range of applications.…”
Section: Experimental Data Setmentioning
confidence: 99%
“…However the presence of octadecylsilane chemical bonds on the surface of Aerosil R R805 avoids that PPG molecules attached to the silica particles and lets them develop a three dimensional network without interacting chemically with polypropylene gycol chains. So a flocculated suspension is formed (Khan & Zoeller, 1993). The steady viscosity curves, shown in Figure 6, represent the steady viscosity reached by the suspensions at different values of shear rates.…”
Section: Experimental Data Setmentioning
confidence: 99%