Effects of Gum Arabic macromolecules on surface forces in oxide dispersions

Leong, Y.K., Seah, Ulric, Chu, S.Y., and Ong, B.C. (2001) Effects of Gum Arabic macromolecules on surface forces in oxide dispersions. Colloids and Surfaces A: physicochemical and engineering aspects, 182 (1-3). pp. 263-268.

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Abstract

The effects of Gum Arabic (GA) on the zeta potential-pH and yield stress-pH behaviour of α-Al2O3, TiO2 and ZrO2 dispersions were evaluated. GA is amphoteric in character as it contains protein fractions. It's macromolecule has a molecular weight ranging from 50 000 to several million. In aqueous solution, the GA molecule assumed a very compact structure. Upon adsorption it will form a relatively thick protrusion from the surface that may act as a steric layer or participate in bridging. At charge neutral condition, GA increased the maximum yield stress, τymax, at pH >5.0 by as much as 60–80% for both α-Al2O3 and ZrO2 dispersions. This strengthening of the network structure was attributed to bridging. In contrast GA decreased the τymax of TiO2 dispersions at pH <5.0. Here the prevailing interaction was steric. Bridging effect was not important because the free carboxylate group, responsible for bridging, was uncharged at pH <5.0.

Item ID: 13149
Item Type: Article (Refereed Research - C1)
Keywords: bridging; dispersions; gum arabic macromolecules; steric; yield stress; zeta potential
ISSN: 1873-4359
Date Deposited: 31 Jul 2012 06:02
FoR Codes: 03 CHEMICAL SCIENCES > 0306 Physical Chemistry (incl Structural) > 030603 Colloid and Surface Chemistry @ 100%
SEO Codes: 86 MANUFACTURING > 8610 Ceramics, Glass and Industrial Mineral Products > 861099 Ceramics, Glass and Industrial Mineral Products not elsewhere classified @ 100%
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