| Abstract: | Several rheological properties of aqueous alginate solution have been investigated in the absence and presence of four divalent cations: Ca, Cu, Mn, and Co. The concentration dependence of viscosity in alginate solution without addition of divalent cations shows a similar behavior to that found for other polysaccharides and synthetic polymers. We have found that for Ca(II) -added systems, sol-gel transition curves for different alginate concentrations can be superimposed over the concentration range of this study by using a normalized parameter. Shear-thinning behavior has been observed for all the alginate solutions by addition of four divalent cations over sol-gel transition process. The values of exponent b in the power-law relation $ {\eta \propto \dot \gamma }$ were found in the range of ?0.3 ～ ?0.6. It is suggested that a considerable portion of divalent cations remains in a cross-linking state even under shear flow. The results obtained from thixotropy measurements indicate the existence of a major framework formed in the gel-like and well-gelled samples, which can be maintained until shear rate (or shear stress) reaches a threshold value. © 1994 John Wiley & Sons, Inc. |
