| 초록 |
The stability of colloidal silica particles was investigated as a function of particle diameter, molecular weight of polyvinyl alcohol, and NaCl concentration. The adsorption of polymer on the surface of partcle was increaced with decreasing the particle size and pH. When pH of the suspension was close at the point of zero charge, all the samples, bare and polymer adsorbed particles, were flocculated. The rheological properties of suspension depend on the degree of the amounts of polymer adsorption and the flocculation. The suspension with complete coverage of the particles and the pH far from the point of zero charge preserve stability, whereas under conditions of partial coverage of the surface, bridging flocculation occurs. The effects of polymer adsorption on the particles and the flow befavior of flocculated systems were studied. The flocs under the shear flow were suddenly disrupted, so that the system showed the shear thinning and the viscoelastic properties. Although the suspension was dilute, the viscoelasticity was investigated at above 7wt% of silica under the high concentration of low molecular weight PVA.
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