Change in the two-step flow behavior on aging the ternary mixture comprising monoalkyl cationic surfactant, long-chain alcohol and water - I. Viscous flow preceded by incipient elastic deformation

摘要

Change in the rheological behavior during aging was monitored by the cyclic shearing tests on the ternary system, comprising cetyltrimethylammonium chloride (C(16)CA), cetyl alcohol (C16OH) and water. In all the stress controlled experiments, typical shear thinning flow was observed at higher shear rate, preceded by an apparent shear thickening behavior below 10(-3) s(-1). From the relationship between the shear stress tau and the strain gamma, however, an elastic deformation was observed at the low-shear region marked by an apparent yield value tau(a). The apparent viscosity of the ternary mixture increased on aging. The maximum apparent viscosity eta(max) increased linearly on aging for 1-3 days, fell discontinuously the decrease in the rate of increase of eta(max). A similar increase and a level off on aging were observed for an apparent elasticity E-a and tau(a). These elastic properties are related to the development of the initial structure. From these observations, a two-step development of the internal structure was proposed. (C) 1998 Elsevier Science B.V. [References: 12]