NMR AND SEDIMENTATION STUDIES OF A POLYMERIC STERIC STABILIZER FOR ALUMINA

The sedimentation behavior of alumina powder has been studied in the presence of polyvinylpyrrolidone (PVP) and poly (vinylpyrrolidone-co-vinyl acetate) (PVP/VA) in both thermodynamically ''good'' and ''poor'' solvents for the PVP homopolymer. PVP/VA provides higher sediment densities than does its PVP homopolymer counterpart. Solution-state C-13-T1 spin-lattice relaxation measurements were made on analogous mixtures both with and without alumina powder. The NMR results suggest that the PVP/VA copolymer is anchored to the alumina powder surface by means of VA moieties, whereas the PVP moieties extend into the continuous phase of the slurry medium. Thus, the higher settling densities that are observed in the presence of PVP/VA can be attributed to a steric stabilization mechanism.