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Langmuir, Vol.16, No.9, 4055-4058, 2000
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 examined by a stress-controlled rheometer and Ubbelohde type viscometer. Under the quiescent state of the SAN/TOL suspensions, the original laminate structure 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 similar to 2 x 10(-3). The dense concentration region exhibits elastic gel-like properties, and rheopexy behavior imposed by shear stress was observed. The limiting value of the dynamic storage modulus G' was given by G'(omega-->0) similar to phi(4), whereas the loss tangent delta exhibited independence of phi and remains at a constant value of about 0.1.
Keywords:PARTICLES