Colloidal dispersion and rheology study of nanoparticles

The effects of dispersant ammonium poly(methacrylic acid) (PMAA-NH₄) and poly(acrylic acid) (PAA) on nano-Al₂O₃ particle dispersion have been investigated. Under the same dispersion viscosity, Al₂O₃ of 38 nm size requires 20 times more PAA dispersant than Al₂O₃ of 0.2 μm size but with only 9 times specific surface area increase. For the same carboxylic acid group to Al₂O₃ mole ratio, the PAA dispersant adsorbs more readily onto nano-Al₂O₃ particles than the PMAA-NH₄ dispersant and has better dispersion efficiency. Rheology measurements confirm the better dispersion and higher dispersion efficiency when PAA is used. Maximum solids loading has been predicted for each suspension based on the rheological data; this predication capability can serve as the important guidance for future dispersion designs.