Problems spanning the boarder across the suspension rheology and fine particles reaction are discussed. Three case studies are given with regard to the change in the rheological behavior of concentrated suspension due to chemical reactions: (1) change in the aggregation morphology in the silica/silica sol suspension on aging, (2) influence of the in situ surface precipitation of indiumtin solid solution on the surface of indium oxide, and (3) effects of surface scratching and aging of soda lime glass particles on the electrorheological properties of their dispersions.
An automatic simulation system of film blowing processing was constructed. Band Matrix method was chosen to solve some differential equations. Newton-Raphson method was combined with it to search. for the most suitable molding conditions automatically. Newtonian fluid was assumed for the polymer melt. The validity of this system was demonstrated by comparison of simulated results to experimental data.
We have investigated the dynamical shear modulus of elastomers within which conducting particles are dispersed. When an electric field is applied, the storage modulus G′ of these“ER elastomers”increases due to the electrostatic forces among the polarized particles, and the electrically induced modulus ΔG′increases as the modulus G′0 of the matrix elastomers decreases.These results are interpreted in terms of a model based on the competition between the electrostatic attractive force among particles and the elastic repulsive force due to the deformation of the matrix.As G′0 decreases. the particles come closer to their neighbors and the electrostatic force increases,and thus ΔG′increases. These findings should find applications in the selection of suitable matrix materials for the ER elastomers.
Rheological behavior was examined for suspensions of PMMA powder/associating polymer solution. Hydrophobically modified ethoxylated urethane (HEUR) was used as the associating polymer. Suspensions showed non-Newtonian flow at lower HEUR concentrations. Flocculation and sedimentation of PMMA powder was induced by the addition of HEUR polymer in this concentration range, suggesting that associating thickners also act as flocculant. Suspensions showed Newtonian flow at higher HEUR concentrations. In this concentration range, aqueous solutions of HEUR showed linear viscoelastic behavior which was caused by networks of hydrophobically associated HEUR polymers. Frequency dependence of the storage modulus and the loss modulus of HEUR solutions and PMMA/HEUR suspensions showed almost straight lines with slopes of 2 and 1, respectively. The relaxation time of HEUR aqueous solutions estimated from master curves was independent of the polymer concentration. The relaxation time of PMMA/HEUR suspensions was almost the same as that of HEUR aqueous solutions. These results imply that the dispersed particle does not affect the lifetime of intermolecular junction. Viscosity and relaxation time of HEUR aqueous solutions showed Arrhenius type of dependence on temperature, but a deviation occured above a certain critical temperature. Flow curves of suspensions changed from Newtonian to non-Newtonian and frequency dependence of moduli yielded a shoulder at this critical temperature even in the higher HEUR concentration range. It is deduced that the association of hydrophobic groups was destroyed by increasing temperature, and resulted in the flocculation of the particles. This temperature-induced flocculation was thermoreversible, because the shoulder in frequency dependency of moduli disappeared with decreasing temperature.
We investigated the dynamic mechanical properties for binary miscible blends consisting of an isotactic polypropylene (PP) and an ethylene-1-hexene copolymer (EHR) of 51 mol% 1-hexene. The film specimens prepared at various isothermal crystallizaiton temperatures were used in this study. The temperature of the mechanical relaxation associated with the crystalline phase above 350 K shifted to higher temperatures as the crystallization temperature and/or the EHR fraction increased. These results imply that the high crystallization temperature and the high EHR fraction lead to well-organized crystalline structure of PP. The PP/EHR blend isothermally crystallized at a lower temperature showed only single peak due to the glass transition at the temperature between those of the pure components, whereas the blend crystallized at a higher temperature showed broad and ambiguous double peaks. It is suggested that the EHR-rich amorphous phase appears during crystallization when the crystallization rate is slow enough for the EHR molecules to diffuse out of the interlamellar region.
Flow of a viscoelastic fluid contained between a stationary inner sphere and a rotating outer sphere is studied experimentally. Relatively low concentration polyacrylamide/water solutions are used as model viscoelastic fluid and glycerin/water solutions are used as the Newtonian fluid for the sake of comparison. In experiments measurements of the stationary torque of the inner sphere are made associated with a flow visualization of uniquely appearing flow modes for viscoelastic fluids. Experimental results revealed that for the first flow transition a roll-cell-like-strucure caused by the elastic instability is generated in the polar region and it propagates toward the equatorial region. A correlation is obtained for the torque data in the regime before onset of the instability.
In this study, the dynamic modulus of some flexible polyurethane foams was determined by the dynamic viscoelastic measurements in compression mode. As the result, the dynamic modulus is found to evaluate compression characteristics of foam as well as other dynamic properties. Especially, the dependence of the dynamic modulus on the initial shrinkage is considered to be important for the understanding of cushion properties. The Young's modulus of the flexible polyurethane foams was evaluated by the finite element method (FEM) using a personal computer. The calculated value following from the two-dimensional model with six-angular pores analyzed by FEM using the plane stress element gave improved agreement with the calculated results of Thomas-Gent and Lederman. Furthermore, the calculation based on the two-dimensional model analyzed by FEM using beam element was found to be in a reasonable agreement with the experimental data for the dynamic modulus of elasticity.
Filling up flows of several molten polymers in a rectangular cavity grooved on a mold surface were experimentally investigated by means of a flow visualization technique. The conditions for the higher mold printability were obtained as a function of polymer melt temperature, mold wall temperature, air blow pressure and air blow velocity.