The influence of concentration and temperature on the rheological behavior of diutan gum aqueous solutions

A thorough rheology characterization of aqueous solutions of diutan gum, in different concentration (2000, 4300, 6000, and 8000 ppm) and temperatures (20, 40 and 60 °C), was conduct in order to determine the following rheological properties: viscosity; storage modulus; loss modulus; complex modulus and complex viscosity. Tests of flow curve, structural recovery, temperature sweep, creep and recovery, frequency sweep and stress sweep were performed. Rheological models were used to fit the experimental data. The aqueous solutions of diutan gum show pseudoplastic and viscoelastic behavior. The Power-Law and the Cross models fit very well the pseudoplastic behavior of aqueous solutions of diutan gum. The storage modulus (G′), in the case of 6000 and 8000 ppm, show larger values compared to loss modulus (G″), indicating a gel behavior for this diutan gum aqueous solutions, in the angular velocities investigated (0.1 to 10 rad/s). For the aqueous solution of diutan gum with 4300 ppm, there is a crossover of the curves of G′ and G″, being G′>G″ for angular velocities greater than 1 rad/s. The exponential model of three parameters fits very well the data of the curves G′ and Gʺ as a function of the angular velocity. The Power Law model fits very well the data of the complex viscosity as a function of the angular velocity. The aqueous solution of diutan gum shows good thermal stability. The study of rheology of aqueous solutions of diutan gum can contribute to better understanding the flow behavior of these biopolymers with many applications.