Thermo-rheology and thermodynamic analysis of binary biopolymer blend: A case study on sage seed gum-xanthan gum blends

Abstract

In this study, the effect of different temperature sweep modes (gradient (TGS), table (TTS) and profile (TPS) at heating/cooling rates of 1, 11 and 36.53 °C/min, respectively) were elaborated on the interaction behavior of biopolymer blends (sage seed gum-xanthan gum (SSG-XG) as a case study at different ratios (1-0, 3-1, 1-1, 1-3, 0-1). Thermodynamic incompatibility of binary blends was determined using dynamic temperature sweep test during heating/cooling stages. All blends were incompatible, as shown by positive values of enthalpy and Gibbs free energy and low negative entropy of mixing. A temperature at which G* changed dramatically showed a good correlation with midpoint glass-transition temperature. TPS as an alternative for TGS could lessen the test time with the additional capability to determine time dependency of samples. Among all dispersions, only SSG and 3-1 SSG-XG were thermorheologically simple during frequency sweep test. With the increase in temperature, the average molecular weight of SSG and XG chains increased and decreased, respectively, while the molar mass distribution of all gum chains increased. The yield stress at both long and short timeframes increased with temperature for SSG and 3-1 SSG-XG, although other dispersions showed the reverse trend. The time dependency of yield stress almost increased with increase in SSG fraction. In addition, a new methodology was proposed to determine a range of stress and timescales for thixotropic or viscoelastic tests. From both the thermodynamic and kinetic viewpoints, 3-1 SSG-XG at 50 °C showed the best synergistic interaction among others.