Browsing by Autor "Lisbeth Manchego"

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Efecto del polímero carboximetil celulosa de sodio sobre la inversión de emulsiones
(2008) María Teresa Celis de Arce; Lisbeth Manchego; Michelle Contreras; Ana María Forgiarini de Guédez; Francia Véjar; Laura Márquez; María Isabel Briceño de Rivas; Jean‐Louis Salager
Phase inversion is the process in which emulsion oil-in-water (O/W) is transformed to water-in-oil emulsion (W/O). There are two types of emulsion inversion. The first one is based on the variation of the system formulation and is called transitional inversion whereas the second one, which takes place when the water/oil ratio is changed, is so -called catastrophic inversion. The latter, depends on the stirring energy and duration, as well as on the viscosity, as well as the viscosity of the oil phase. The present study reports the effect of an increase of aqueous phase viscosity by adding an anionic polymer (carboxymethylcellulose sodium salt) on phase behavior and standard inversion boundary. The effect of the stirring energy is also reported. The results indicate that the addition of carboxymethylcellulose alters the formulation, which results in variations in phase behavior and standard inversion boundary. It is shown that an increase of the aqueous phase viscosity produces a considerable increase in the three phase’s region in the equilibrated systems until a viscosity of 0.5 Pas is attained, with an insignificant increase on this zone between 0.5- 1Pa.s. An increase in the viscosity of the aqueous phase also shifts the catastrophic branch of the standard inversion line, hence reducing the region of O/W emulsions for viscosities lower than 0.5 Pa.s. and this line keeps constant for higher viscosities.
Inversión de emulsiones incluyendo acrilatos en la formulación
(2009) María Teresa Celis de Arce; Jesús Calderón; Lisbeth Manchego; Ronald Mercado; Jorge Avendaño; Jean‐Louis Salager
The effect of the aqueous phase viscosity on phase behavior and standard inversion boundary has been studied on equilibrated systems and the dynamic emulsion inversion in the direction abnormal normal (C+?A+ y B-?A-), has been always discussed on systems formed by sodium dodecyl benzene sulphonate (SDBS)-sodium dodecyl sulphate (SDS), water, kerosene and pentanol. The change of the aqueous phase viscosity is produced by adding polyacrylate (textilan 567) to aqueous solutions, in where the pH is adjusted with the addition of ammonium hydroxide. The results indicate that the addition of polyacrylate alters the formulation, which results in variations in phase behavior and standard inversion boundary. An increase in the viscosity of the aqueous phase shifts the catastrophic branch of the standard inversion line (B-/A-), hence reducing the region of O/W emulsions. In addition, an increase in the viscosity of the aqueous phase in dynamic inversion process leads to a change of inversion line in the direction (B-/A- and C+/A+) toward higher and lower water percentages respectively.