The shear flow properties of M1

Abstract

Steady, transient and oscillatory shear flow experiments were performed on the “round robin” fluid M1, using both a Weissenberg Rheogoniometer and a Carri-Med Controlled Stress Rheometer, at several different temperatures. In steady shear, up to a shear rate of 70 s −1, the viscosity remained constant. Thereafter, the fluid was seen to shear thin slightly. The first normal stress difference was found to correlate with the square of the tangential stress, independently of temperature. In transient shear on the Rheogoniometer, stress overshoots were observed above a shear rate of 70 s −1. These were quite substantial for the first normal stress difference. On the Controlled Stress Rheometer, above a critical shear stress of 180 Pa, M1 began to shear thicken. In oscillatory shear, the data obtained at different temperatures were reduced to a master curve, which was found to fit an Oldroyd B model up to a reduced frequency 15 s −1, but which diverged thereafter. At 20 ° C, the relaxation time was found to be 0.34 s.