Characteristics of Alkyltrimethoxysilane-Treated Fumed Silicas and Rheological Behavior of Fumed Silica Suspensions in an Epoxy Resin

• Published in: Journal of colloid and interface science Vol. 239; no. 2; pp. 555 - 562
• Main Authors: Shirono, H., Amano, Y., Kawaguchi, M., Kato, T.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.07.2001; Elsevier
• Subjects: aggregation; alkyl chain length; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; rheological behavior; silica–epoxy resin suspension; surface-modified fumed silica; rheological behavior; silica–epoxy resin suspension; aggregation; alkyl chain length; surface-modified fumed silica; Viscosity; Chain length; Epoxy resin; Organic silane; Particle suspension; Experimental study; Surface treatment; Aggregation; Bisphenol A; Adsorption; Alkyl; Silicon Oxides; Property structure relationship; Rheological properties
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.2001.7604

Fumed silica was surface treated by hexyl (C6), octyl (C8), decyl (C10), hexadecyl (C16), and octadecyl(C18)trimethoxysilanes, and the products were evaluated from various aspects. The amounts of alkyl group introduced on silica surface were all within the range from 22 to 25 mmol/100 g. Such fumed silicas were suspended in an epoxy resin, bisphenol type A, and their rheological properties were measured. The rheological behavior of the silica suspensions was investigated as to steady-state viscosity and dynamic moduli in order to examine the effect of alkyl chain length on interactions of hydrophobic groups on the silica surface. The stronger shear thinning behavior was observed in the surface-modified fumed silica with longer alkyl groups. However, the suspensions of the nontreated fumed silica and the fumed silicas treated by C6 silane showed Newtonian behavior even at the silica concentration of 7 wt%. The dynamic moduli G′ of the silica suspensions increased with increasing alkyl chain length. The interaction of hydrophobic groups on the silica surface is mainly attributed to the rheological behavior of fumed silica suspensions in the epoxy resin.