Modification of silicon nitride slip properties by poly(acrylic acid)

Acrylic-acid based polyelectrolytes are used for dispersion and rheology control of ceramic powder slips. This study focuses on the Si{sub 3}N4/H{sub 2}O/poly(acrylic acid) (PAA) system, with the goal of improving our basic understanding of the mechanisms which may significantly affect slip properties during processing. A variety of experimental techniques were employed, including potentiometric titration, electroacoustic analysis, adsorption isotherms, and controlled-stress rheology. The slips exhibited complex behavior over a wide range of conditions in which solids concentration, PAA molecular weight and concentration, and pH were varied. Polymer charge and conformation were found to have significant impact on the flow properties. Pseudoplastic behavior was attributed to the presence of free polymer. The flow properties were also found to be highly pH dependent.