title: Viscosity and temperature relationship in ethanol/water mixtures gelified with Carbopol Ultrez 10.
abstract: The rheological characterization of Carbopol Ultrez 10 ethanolic (15%) gels is complemented by studying flow behavior as a function of temperature (20-50 degrees C) at different pH (4.0-7.0) and polymer concentrations (0.1-0.5%). Flow curves were adjusted to the Ostwald model, showing a fall in viscosity, together with an enhancement in flow index with increasing temperature. Calculated flow activation energies at constant shear rate (Egamma) were found to be related to the final pH of hydroalcoholic gels. Nevertheless, at the polymer concentration range evaluated, no significant correlations were obtained between activation energy and concentration. In general, the Carbopol Ultrez 10 gels exhibit little viscosity change under the temperature variations of normal use and storage, which minimizes possible unacceptable changes in the product's characteristics.
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, Alcalá University, Madrid, Spain. mjose.fresno@uah.es
authors.forename: M J
authors.initials: MJ
authors.lastname: Fresno Contreras
authors.forename: A
authors.initials: A
authors.lastname: Ramírez Diéguez
authors.forename: M M
authors.initials: MM
authors.lastname: Jiménez Soriano
mesh_terms: D000180:Acrylic Resins; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004337:Drug Carriers; D000431:Ethanol / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D011145:Polyvinyls / Q000737:chemistry*; D013696:Temperature; D014783:Viscosity; D014867:Water
chemical_list: D000180:Acrylic Resins; D004337:Drug Carriers; D005782:Gels; D011145:Polyvinyls; D014867:Water; C006912:carboxypolymethylene; D000431:Ethanol