Rheological study of Carbopol (R) Ultrez (TM) 10 hydroalcoholic gels, I: Flow and thixotropic behavior as a function of pH and polymer concentration

The rheological behavior of Carbopol(R) Ultrez(TM) 10 alcoholic (30%) gels was studied as a function of two main variables: pH (4.0-7.0) and polymer c oncentration (0.1-0.5%). Flow curves of all hydroalcoholic gels. were adjus ted to the Ostwald model. Empirical functions are obtained to describe the individual dependence of calculated consistency and flow index, and hence o f-the structural development of the polymer network, on the variables studi ed. Finally, by substituting in the power law expression, an empirical mode l is given to estimate viscosities of gels for any pH value and polymer con centration in the ranges evaluated. The results of a further study are give n, performed to assess the effect of shear time on gel viscosity and thixot ropic properties. In general, the hydroalcoholic gels showed no significant thixotropic behavior, with a remarkable stability under the shear conditio ns evaluated.