Rheological Behavior and Structure of a Commercial Esterquat Surfactant Aqueous System

Abstract

Aqueous dispersions of a commercial esterquat-type surfactant widely used in fabric softeners were rheologically characterized. While at 4 wt % esterquat concentration, a Newtonian response was observed; non-Newtonian (Sisko) flow behavior and viscoelastic properties were found at 12 wt % and higher concentrations. The onset of nonlinear viscoelasticity in oscillatory shear provided interesting information on the strength of quiescent surfactant aggregates. Mechanical spectra corresponded to the plateau zone and the onset of the transition zone. The plateau modulus and the characteristic slopes of the relaxation spectra depended on the strength of the interactions among the aggregates. Start-up at the inception of the shear experiments were carried out to obtain information on the time-dependent shear behavior. Cryo-SEM micrographs demonstrated the occurrence of a dispersion of vesicles embedded into a bilayer matrix.

Rheological and Microstructural Behavior of a Model Concentrated Fabric Softener

“…However, a typical formulation of liquid softener may also contain nonionic surfactant, antibacterial and preservative agents, dyes, and fragrances [19]. New data and information provided by this work completes previous studies of systems with T1 surfactant [16,20] and contributes relevant information for scientific research and industrial application.…”

“…Upon increasing shear rate, the shear stress increased after a certain shear time period indicating the possible appearance of antithixotropy, if the build-ups of viscosity were reversible after a certain rest time. However, previously reported results on these systems revealed that the viscosity build-up phenomena turned out to be irreversible at least for a very long period of rest time [16]. Therefore, this behavior will be called apparent antithixotropy.…”

“…Lamellar phase transitions have been studied in anionic surfactant systems [12][13][14], an anionic and amphoteric surfactant mixture [9], cationic and nonionic surfactant mixtures [9], polymeric surfactants [10], and cationic surfactants [15]. These transitions were also observed in double-chain ionic surfactant systems [16] which are the focus of this study.…”

“…This fact may be attributed to bilayer flexibility reduction provoked by an increase of ionic strength. As a consequence, higher mechanical energy was required for the formation of vesicles [12,16].…”

Physical Characterization of a Commercial Suspoemulsion as a Reference for the Development of Suspoemulsions

“…This corresponded to the plateau zone of the mechanical spectrum. This window of the mechanical spectrum is related in polymer rheology to the occurrence of macromolecular entanglements [15] and has also been found in concentrated emulsions [16], concentrated solutions of polymers [17,18], micellar solutions [19], and in a protein-polysaccharide system in aqueous dispersions [20]. A similar behavior to that of this suspoemulsion has been found for hydrophobically modified alkali-soluble emulsions [21].…”