Viscosity properties of gelatin in solutions of monovalent and divalent Salts

The viscosity behaviors of gelatin with and without salts were examined in details by a rotational viscometer and a horizontal gravitational capillary viscometer, ranging from extremely dilute to entangled regimes. It was found that gelatin in salt free solution behaviors as neutral polymer in theta solvent. Polyelectrolyte effect can be found in extremely dilute regime. For gelatin/NaCl solution, the concentration dependence of specific viscosity showed that gelatin behaviors as neutral polymer in good solvent. The two critical concentration c* and c (e) of gelatin solutions with and without NaCl moved from 4.0 wt% and 14.0 wt% to 2.0 wt% and 12.0 wt%, respectively. Addition of salts can improve the gelatin viscosity. It is the characteristic of a polyampholyte. The viscosity increased more significantly in CaCl2 than that in NaCl solutions. Moreover, the effect of Ca2+ is notable in gelatin solution with high concentrations, especially in entangled solutions.