Modeling the Dynamic Rheological Bebavior of Agar Based Aqueous Binders

This study proposes a fundamental microstructural/rheological model for agar gels that describes their dynamic rheological behavior during gelation. The concept of a sigmoidal type temperature dependence of the monomeric friction coefficient, ξ o , of the agar molecule is introduced to describe the increase of relaxation times of the agar molecules with decreasing temperature. At high temperatures (close to 373 K), the model behaves like a dilute solution of flexible polymers. At low temperatures (close to 273 K) contributions from an equilibrium modulus term are predominant. Dynamic rheology was employed to study the applicability of this model for agar gels. Gelation curves were obtained experimentally for various agar concentrations and cooling rates were fitted successfully to the theoretical model predictions.