Rheology of highly concentrated anionic surfactants

• Published in: Rheologica acta 2006-08, Vol.45 (6), p.891-898
• Main Authors: MONGONDRY, Philippe, MACOSKO, Christopher W, MOADDEL, Teanoosh
• Format: Article
• Language: English
• Subjects: Chemistry; Crystals; Exact sciences and technology; General and physical chemistry; Liquid crystals; Microfracture; Oleic acid; Organic chemistry; Phase diagrams; Rheological properties; Rheology; Shear flow; Shear modulus; Shear rate; Shear strain; Sodium salts; Solution properties; Solutions; Surface physical chemistry; Surface-active agents: properties; Surfactants; Ternary systems; Viscoelasticity; Wall slip
• ISSN: 0035-4511; 1435-1528
• DOI: 10.1007/s00397-006-0090-6

Surfactant solution flow behavior is of great importance to both the chemical and consumer product industries. Most studies on the flow behavior of surfactant solutions, however, have focused on the dilute regime. Seldom reported is rheology in the highly concentrated regime where typically these surfactants are processed and delivered. First, we present here the phase diagram for the ternary system: water and two anionic surfactants (sodium salt of lauric and oleic acid) at different temperatures. Then, we present both linear viscoelastic and steady shear flow results in the high (70 to 90%) surfactant regime. We find that high values of the shear modulus are directly dependent on the quantity of surfactant crystals and that the formation of a lamellar liquid crystal phase at 45°C affects both modulus and flow of the system. Lamellar crystals create a stiff network resulting in wall slip at large shear strain. Using serrated plates removes slip at the wall and we find a shear rate where microfractures localize in a preferential plane and the material flows. This behavior is reversible.