CHANGE IN THE 2-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

Change in the rheological behavior during aging was monitored by the c yclic shearing tests on the ternary system, comprising cetyltrimethyla mmonium chloride (C(16)CA), cetyl alcohol (C16OH) and water. In all th e stress controlled experiments, typical shear thinning flow was obser ved at higher shear rate, preceded by an apparent shear thickening beh avior below 10(-3) s(-1). From the relationship between the shear stre ss tau and the strain gamma, however, an elastic deformation was obser ved 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 e ta(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 r elated to the development of the initial structure. From these observa tions, a two-step development of the internal structure was proposed. (C) 1998 Elsevier Science B.V.