Dynamic rheological properties of mixed carrageenan gels under large strains

In this experiment, large amplitude oscillatory shear, differential strain and pre-stress measurements were performed on sample solutions of mixed kappa carrageenan and iota carrageenan solutions. As measurements enter the nonlinear regime, properties of soft materials and complex fluids yield a wide array of responses due to flow instabilities or network structure. LAOS experiments reveal that mixed carrageenan solutions exhibit intermediate properties of the kappa and iota components. At large enough strains, all gels exhibit strain softening in the elastic moduli due to irreversible deformations introduced in the gel networks. However, there is an expressed increase in the viscous moduli of both iota and the mixed gel until both transitions from a predominantly elastic to a viscous material. The softening of the elastic moduli and expressed increase in the viscous moduli is a hallmark behavior of soft glassy materials.