Dispersed structure and rheology of lipophilized-smectite/toluene suspensions

Dispersed rheology of lipophilized-smectite (SAN)/toluene (TOL) suspensions with various concentrations phi of (0.03-3.77) x 10(-2) vol fraction was e xamined by a stress-controlled rheometer and Ubbelohde type viscometer. Und er the quiescent state of the SAN/TOL suspensions, the original laminate st ructure in the solid state of SAN was lost and exfoliation of the silicate layers took place as revealed by X-ray diffraction analysis. In the dilute SAN/TOL suspension with 10(2)phi less than or equal to 0.2, the value of n( sp)/phi (n(sp) being specific viscosity) is independent of concentration up to phi similar to 2 x 10(-3) and exhibits abrupt increasing beyond phi sim ilar to 2 x 10(-3). The dense concentration region exhibits elastic gel-lik e properties, and rheopexy behavior imposed by shear stress was observed. T he limiting value of the dynamic storage modulus G' was given by G'(omega-- >0) similar to phi(4), whereas the loss tangent delta exhibited independenc e of phi and remains at a constant value of about 0.1.