Dispersing Properties of Copolymers Able to Act as Binders

Abstract

Macromolecules, containing both charged groups (COO− and SO3−), in order to ensure powder dispersion, and neutral groups (vinyl alcohol and ethyl hydroxyl acrylate), in order to obtain enough strength in the green parts, were synthesized to be used in the dry pressing process. The evaluation and the comparison of the capacity of these synthesized copolymers with disperse alumina particles in aqueous media are considered in this paper. Both COO− and SO3− ionized groups are responsible for strong adsorption onto alumina surface and can promote sufficient electrostatic repulsive forces to achieve a good state of dispersion. The role of the copolymers in the stabilization of alumina suspensions was found to be greatly affected by the nature and by the fraction of groups in the macromolecular chains. A low concentration of copolymers (0.5 wt% on alumina basis) containing 35% of carboxylic groups and 65% of vinyl alcohol groups (PV35) or containing 55% of carboxylic groups and 45% of hydroxy ethyl acrylate groups (EH2A55) leads to stable alumina suspensions with a low viscosity similar to that obtained with a classical ammonium polymethacrylate (between 10 and 20 mPa·s for 27 vol% alumina suspensions). Copolymers containing sulfonate groups are less efficient.