ABSTRACT

In order to obtain high solids loading and low-viscosity slips that are needed for the various shape-forming processes, it is important to understand the three-way interactions between solvent, particles and dispersant. The understanding will also help in optimization of the rheological properties of these systems. The preparation of stable, concentrated powder dispersions in organic or aqueous solvents requires an effective stabilization of particles in the medium. Dispersants allow control of the interparticle forces and thus result in powder deagglomeration and stabilization of particles in a suspension. Colloidal stability is generally achieved by steric or electrostatic repulsive potentials that oppose the van der Waals attractive potential. Electrostatic contributions are dominant in aqueous systems because of the high dielectric constant of water. Typical dispersants in water dissociate into ions that preferential1y adsorb on the particle surface generating a surface potential resulting in electrostatic repulsion. Even in the absence of dispersants, charge gen-

eration occurs by the protonation or deprotonation of chemically active (acidic or basic) sites on the particle surface. As compared with nonaqueous systems, charge generation mechanisms in aqueous systems are relatively simpler and well understood [1-5].