Rheological study of Carbopol (R) Ultrez (TM) 10 hydroalcoholic gels, II: Thermal and mechanical properties as a function of pH and polymer concentration

The rheological characterization of Carbopol(R) Ultrez(TM) 10 alcoholic (30 %) gels is complemented by studying flow behavior as a function of temperat ure (20-50 degrees C) at different pH values (4.0-7.0) and different polyme r concentrations (0.1-0.5%). Flow curves were adjusted to the Ostwald model , showing a fail in viscosity, together with an enhance in flow index with increasing temperature. Calculated flow activation energies at constant she ar stress (E-tau) and at a constant shear rate (E-gamma) were found to be r elated to the final pH of the hydroalcoholic gels. A further study was done to evaluate hardness (H) and compressibility (A) of gels as a function of pH and polymer concentration, obtaining similar correlation patterns for me chanical properties and consistency indexes. A significant linear dependenc e was also found between consistency indexes and the mechanical properties of the gels.