On the Dynamic Viscoelastic Properties of Glass Beads-Polystyrene Solution Systems

Abstract

The dynamic viscoelastic properties of disperse systems containing some glass beads or aerosil powder in polystyrene solution were investigated using a coaxial cylinder viscometer. The results obtained are as follows:(1) The frequency dependence curves of the storage modulus G′ and the loss modulus G″ show the remarkable second plateau which was given by Onogi and his co-worker at fairlylower frequency range below so-called rubbery region. However, when these suspensions are sheared by violent disturbance, this plateau is completely disappeared.(2) Moreover, the height of this plateau has the tendency to increase with increasing particle concentration and with decreasing particle size. In the case of the suspension containing glass beads having larger than 30μ this plateau can not be observed as shown Fig. 11.(3) As a distinguishing behavior peculiar to the suspensions, two mechanisms are introduced; those are, (a) the thixotropic softening behavior caused by violent shearing disturbance and (b) the rheopectic hardening behavior caused by gentle oscillation.(4) The suspensions show nonlinear viscoelastic behavior at high concentration and low frequencies. Two kinds of nonlinearity are analyzed here; those are, (a) dependency of nonlinear behavior on the strain amplitude observed at higher measuring frequencies, and (b) distortion of Lissajous' figure from elliptical shape which is typical linear viscoelastic response.