A generalized model to predict the viscosity of solutions with suspended particles. III. Effects of particle interaction and particle size distribution

The generalized suspension viscosity equation utilized in this study was evaluated with both a packing fraction, φ n , and a particle interaction coefficient, σ, as a function of suspension blend composition, f 2 T . The estimation of the packing fraction, φ n , in turn, required the further elucidation of the D 5 / D 1 ratio of particle diameter averages. Blend constants developed in this study allowed evaluation of both the D x / D y ratio of particle diameter averages as well as the number‐average particle diameter, D 1 , as a function of the fraction of one suspension in a blend, f 2 T . These blend constants were shown to be easily evaluated from each individual suspension prior to blending. The viscosity data of Johnson and Kelsey were shown to be generally predicted as a function of the volume composition when a constant particle interaction coefficient, σ, was assumed. However, a better prediction of the results of Johnson and Kelsey was obtained by assuming that the particle interaction coefficient, σ, was a function of the number‐average particle diameter, D 1 , of the suspension mixture composition. Consequently, a new approach was identified to evaluate the simultaneous effects of small particles to both increase viscosity as a result of increasing particle interaction as well as to decrease viscosity as a result of improving the particle‐size distribution. © 1993 John Wiley & Sons, Inc.