Plasticizing Aqueous Suspensions of Concentrated Alumina with Maltodextrin Sugar

Abstract

Aqueous suspensions of submicrometer, 20 vol% Al 2 O 3 powder exhibited a transition from strongly flocculated, thixotropic behavior to a low‐viscosity, Newtonian‐like state upon adding small amounts of maltodextrin (0.03 g of maltodextrin/(g of Al 2 O 3 )). These suspensions could be filter pressed to highly dense (57%) and extrudable pastes only when prepared with maltodextrin. We analyzed the interaction of maltodextrin with Al 2 O 3 powder surfaces and quantitatively measured the resulting claylike consolidation, rheological, and extrusion behaviors. Benbow extrusion parameters were comparable to, but higher than, those of kaolin at approximately the same packing density of 57 vol%. In contrast, Al 2 O 3 filter cakes without maltodextrin at 57 vol% density were too stiff to be extruded. Measurements of rheological properties, acoustophoresis, electrophoresis, sorption isotherms, and diffuse reflectance Fourier infrared spectroscopy supported the hypothesis that sorbate‐mediated steric hindrance, rather than electrostatic, interparticle repulsion, is important to enhancing the consolidation and fluidity of maltodextrin–Al 2 O 3 suspensions. Viscosity measurements on aqueous maltodextrin solutions indicated that free maltodextrin in solution does not improve suspension fluidity by decreasing the viscosity of the interparticle solution.