CORRELATION OF VISCOELASTIC PROPERTIES OF STABLE AND FLOCCULATED SUSPENSIONS WITH THEIR INTERPARTICLE INTERACTIONS

This review starts with a general introduction on the properties of co ncentrated suspensions. The distinction between ''dilute'', ''solid'' and ''concentrated'' suspensions is given in terms of the balance betw een Brownian, hydrodynamic and interparticle interactions. A section i s given on interparticle interactions and their combinations. The four different types of interactions, namely hard-sphere, electrostatic, s teric and van der Waals are described. The flocculation of both electr ostatically and sterically stabilized suspensions is also discussed. T he next section covers the principles of rheological measurements. Tra nsient (static), dynamic (oscillatory), shear wave propagation and ste ady state measurements are described. The last part of the review deal s with the viscoelastic properties of concentrated suspensions. Four d ifferent systems were described and examples were given: (a) Suspensio ns with hard-sphere interactions; (b) Stable systems with soft (electr ostatic) interaction; (c) Sterically stabilised systems; (d) Flocculat ed and coagulated systems. Both weakly and strongly flocculated system s were discussed. In the above review, particular emphasis was given t o the relationship between the viscoelastic properties of concentrated suspensions and their interparticle interactions. As far as was possi ble, the results obtained from rheological measurements were quantitat ively analysed in terms of such interparticle forces. The review demon strated that such correlation is generally followed and this illustrat ed the powerful use of rheology for studying interparticle interaction s.