PAA/PEO comb polymer effects on rheological properties and inter-particle forces in aqueous silica suspensions.
The effects of a poly(acrylic acid) (PAA)-poly(ethylene) (PEO) comb polymer dispersant on the rheological properties and inter-particle forces in aqueous silica suspensions have been studied under varying pH conditions. The comb polymer was found to adsorb more strongly under acidic than basic conditions, indicating that the PAA backbone of the copolymer preferentially adsorbs onto silica surfaces with the PEO "teeth" extending out from the surface into the solution. In the presence of low concentrations of copolymer, the silica suspensions were stable due to electrostatic repulsions between the silica surfaces. At higher copolymer concentrations and under neutral and basic conditions, where the copolymer interacted only weakly with silica, the suspensions showed a transition from a dispersed to weakly flocculated state and attractive forces were measured between silica surfaces. Under acidic conditions, the silica dispersion also destabilized at intermediate copolymer adsorbed density and then was re-stabilized at higher adsorbed coverage. The silica suspensions were stable at high copolymer coverage due to steric repulsions between the particles. The destabilization at intermediate coverage is thought to be due to polymer bridging between particles or possibly depletion forces.
Whitby
Catherine P
CP
Particulate Fluids Processing Centre, School of Chemistry and Department of Chemical and Biomolecular Engineering, University of Melbourne, Melbourne, Victoria 3010, Australia. c.p.whitby@hull.ac.uk
Scales
Peter J
PJ
Grieser
Franz
F
Healy
Thomas W
TW
Kirby
Glen
G
Lewis
Jennifer A
JA
Zukoski
Charles F
CF