1999 Volume 27 Issue 3 Pages 149-154
Experimental results on rheological behaviors of concentrated suspensions are presented. Suspensions of acryl-styrene copolymer particles with a radius of 45 nm dispersed in water was used as samples. Rheological properties were measured at particle volume fractions φ ranging from 0.177 to 0.462. The time-volume fraction superposition principle was found to be applicable for the suspensions, namely frequency dependence curves with different φ could be reduced to one master curve by shifting horizontally and vertically with shift factors, aφ and bφ. The reological data were rescaled using the effective volume fraction φeff calculated from the effective radius estimated as a sum of the Debye length and the particle radius. With the rescaling, the φ dependency of η0/ηm and η∞/ηm became in good agreement with those of ideal suspensions of rigid spheres, which shows that the Brownian contribution is the origin of the linear viscoelastic behavior. It is likely that the Brownian motion is affected by restraint of neighboring particles in the high φ region so that relaxation time may increase rapidly in the high φ region.