1990 Volume 18 Issue 3 Pages 140-144
Dynamic viscoelastic properties of aqueous solutions of sodium alginates and alginate/calcium complex were measured in the presence and in the absence of free-state ions (external salt). The M/G ratios of these alginates are ranging from 0.21 to 0.88. Dynamic modulus G′of the sodium alginates in a low frequency region increases with the addition of the external salt CaCl2 and G′in a high frequency region is almost independent of the concentration of CaCl2.
On the other hand, in the absence of free ions, dynamic modulus of the aqueous solutions of alginates, in which Na ions are substituted partially by Ca ions, increases with increasing calcium content over the measuring frequency region. That is, from a rheological viewpoint, a complex structure between alginate residues and Ca ions works as a heterogeneous relaxation unit having a relatively long relaxation time in the presence of free ions and it works as a crosslinking point in the absence of free ions.
