THE RHEOLOGICAL AND COLLOIDAL PROPERTIES OF BENTONITE DISPERSIONS IN THE PRESENCE OF ORGANIC-COMPOUNDS .2. FLOW BEHAVIOR OF WYOMING BENTONITE IN WATER-ALCOHOL

The flow behaviour of Wyoming bentonite dispersions was studied in wat er and water-alcohol mixtures (methanol, ethanol, n-propanol) with or without the addition of NaCl. The yield value tau(o) and relative appa rent viscosity tau(rel) (= tau* (dispersion/tau* (medium) at gamma = 94.5 s-1) increase to a maximum and then decrease with increasing alco hol content. The increase of the flow values is caused by face-to-face aggregation. Formation of band-type networks is a consequence of the enhanced attraction between the silicate layers in water-alcohol mixtu res. At higher alcohol contents the bands are contracted to discrete p articles. Both effects are considerably strengthened by calcium ions w hich are present in the crude bentonite.