Effects of Temperature, Surfactant, and Salt on the Rheological Behavior in Semidilute Aqueous Systems of a Nonionic Cellulose Ether

Abstract

Oscillatory shear experiments have been carried out on thermoreversible gelling and nongelling semidilute aqueous systems of ethyl(hydroxyethyl)cellulose (EHEC) (at a constant polymer concentration of 1 wt %) in the presence of various amounts of sodium dodecyl sulfate (SDS) and at some different levels of NaCl addition. Depending on the concentrations of surfactant and salt, a temperature-induced sol-gel transition or only a viscosification of the solution was observed. For the gelling systems, the value of the gel temperature, determined by the observation of a frequency independent loss tangent, was found to be dependent on the composition of the system. At the gel temperature, a power law frequency dependence of the dynamic storage modulus (G‘ ∼ ωn‘) and loss modulus (G‘‘ ∼ ωn‘‘) was constantly observed with n‘ = n‘‘ = n. Values of the viscoelastic exponent n in the range 0.3−0.4 were reported. The value of n, as well as the gel strength parameter S, was dependent on the composition of the system. The...