Textural properties of agarose gels. I. Rheological and fracture properties

Abstract

Small- and large-strain rheological methods were used to develop rheological profiles of agarose gels, including linear, non-linear, and fracture properties. Gel properties were examined under conditions of varying agarose concentration (0.5–2.5% w/w), glycerol concentration (0–60% w/w), and strain rate (0.0017–0.17 s −1). Small-strain behaviors were primarily elastic with only slight frequency dependence. Large-strain behaviors and fracture properties were dependent upon strain rate, agarose and glycerol concentration. Increasing concentrations of agarose produced an increasingly stronger, more brittle network, while increasing concentrations of glycerol produced an increasingly stronger, more deformable network. All fracture properties and non-linear behaviors increased with increasing strain rate in a similar manner, suggesting a general mechanism responsible for strain rate effects that is similar for non-linear and fracture behavior. Increasing concentrations of agarose and glycerol, respectively, increased and decreased the strain rate dependence of non-linear behavior. Phenomenological models were evaluated for describing non-linear behavior. A second-order polynomial equation was determined to describe the data more accurately than the commonly used BST equation [Blatz, P. J., Sharda, S. C., & Tschoegl, N. W. (1974). Strain energy function for rubberlike materials based on a generalized measure of strain. Transactions of the Society of Rheology, 18 (1) 145–161.], providing an estimated parameter that allowed relative non-linear behavior to be reliably quantified.