RHEOLOGICAL STUDIES ON AQUEOUS COLLOIDAL DISPERSIONS OF SYNTHETIC SMECTITE POLY(ETHYLENE GLYCOL) COMPLEXES

In order to study the stabilization mechanism of plate-shaped inorgani c compound/water-soluble polymer complex dispersions in detail, rheolo gical properties were examined. The structural dependence of the fluid ity of dispersions is discussed on the basis of experimental results. A Na-type colloidal silicate with 3-octahedral smectite structure was used as a plate-shaped inorganic compound. Poly(ethylen glycol) (PEG) was used as water-soluble polymer. The mixtures of the silicate and PE G4000 (M(w) = 4000) with the prescribed composition were homogenized b y the use of both an ordinary homomixer (1500 rpm) and an ultrahigh-pr essure homogenizer (more than 100 MPa). The dynamic rheological measur ements were carried out with frequency sweep and % strain sweep using a parallel-plate rheometer. The difference of emulsification procedure s caused the different rheological behaviors of these samples. It was concluded by the use of a Cryo-SEM electron microscopic observation th at the plate-shaped inorganic compounds formed the specific bulky stru ctures, such as card-house, and these structures were modified with po lymer adsorption layers on the surfaces of inorganic compound. The mod ifications of dispersion structures were responsible for rheological p roperties.