The rheological properties of suspensions of Aerosil in Separan solutions were studied by a coaxial cylinder rheometer. The zero-shear viscosity η0 increased at first with Aerosil concentration and showed a maximum at 1 wt%. Further addition of Aerosil led to a decrease in the viscosity, and at concentration>2 wt%, the zero-shear viscosity was lower than that of the medium. The concentration dependence of the storage and loss moduli was similar to that of the η0. The maximum relaxation time τ1 evaluated from relaxation modulus through the Procedure X decreased with increasing Aerosil concentration. Adsorption experiments showed that a large amount of polymer was adsorbed on the dispersed particles. It is concluded that the decrease in polymer concentration in the liquid phase by adsorption is primarily responsible for the decrease in the η0 of the suspension. The rheological properties of suspensions varied with preparation process. This may be due to the difference in the situation of adsorbed polymer.
Relations between the rheological properties and the degree of aggregation of dispersed particles were investigated for suspensions of photosensitive particles. Photosensitive particles were prepared by introducing cinnamoyl group _??_ into styrene-divinylbenzene copolymer particles through the reaction with sodium cinnamate. The photocrosslinking reaction between particles, i. e. the degree of aggregation of photosensitive particles, was controlled by adjusting the irradiation time of a light. The steady-flow and dynamic viscoelastic properties of disperse systems of these particles in diethylphthalate were measured by a cone-plate type rheometer, and the degree of aggregation of particles was measured by the light scattering method. The latter is based on the increase in intensity of forward scattering with increasing aggregation. Shearing stress and dynamic viscoelastic functions increase with increasing degree of aggregation, and the so-called second plateau, which corresponds to the relaxation of the aggregate structure, begins to be observed with it. The relaxation time of disperse systems was also related quantitatively to the degree of aggregation.
To clarify elastic characteristics of disperse systems of tobacco powder and water, the complex dynamic shear modulus γ* and the complex dynamic tensile modulus E* are measured by the forced vibration method, and the effects of porosity and additives on these moduli are examined. The following results have been obtained; the values of |E*| are about 4 times of these of |γ*| for the samples having the same stress history, and the effects of sample shape on these moduli are negligible. The effects of porosity on |E*| is not explained by the effective area of tobacco powder and water in the cut section of sample. To increase E*, carboxymethyl cellulose (CMC) as a binder, pulp as a reinforcement material are used. |E*| is not affected by the addition of CMC at concentration of 0.9~4%, but is affected remarkably by the addition of pulp. |E*| increases with increase in pulp content. Filling value is highly correlated with |E*|, and increases with E* of the system. It is clarified that the addition of pulp is effective to improve the filling value of the reconstituted tobacco.
In order to disclose the smash feeling of ping-pong balls, regional and directional differences of dynamic compression stiffness of a ball were investigated for conventional celluloid balls and newly designed plastic balls by a viscoelastic spectrometer. In the conventional celluloid balls, the dynamic compression stiffness of the equatorial (connected) part of the ball at 15 Hz averaged 6.5×107 dyne/cm, and the phase-lag was about 4 degrees. The equatorial measurements gave 1.5 times the compression stiffness of the polar regions and about the same degrees of phase-lag. On the other hand, plastic balls generally had increased values of dynamic stiffness at the polar part and decreased values of stiffness at the equatorial part, and the plastic balls also indicated strain-rate sensitive mechanical behavior. These facts indicate that the newly designed plastic ball tends to be hard and metal-like when it is smashed in play.
Carbon black-linseed oil suspension shows remarkable thixotropy and structural viscosity attributed to a denser structural network of carbon black particles. In order to provide new concepts for these phenomena, creep compliance J(t) and creep recovery were measured under conditions of various flow histories and different rest periods applied prior to the measurements. With increasing the rest periods, values of J(t) decrease and time dependences of J(t) change peculiarly, corresponding to formation and break-down of the structural network of carbon black particles. However, the values and time dependences of J(t) does not change with rest period when the process of breaking and formation of network structure has attained equilibrium. For carbon black-linseed oil suspension, elastic recovery shows a more complicated behavior depending on creep time than that for concentrated polymer solutions.