Flow Properties of Polymer Solutions. I. Temperature Dependence of Stresses Following Sudden Start and Cessation of Steady Shear Flow

Abstract

Following sudden start and cessation, respectively, of steady shear flow, stresses, κη(t, κ) and κη(t, κ), were measured for a 20-% solution of polystyrene in chlorinated biphenyl. Here κ is the rate of shear and t is the time after sudden change of rate of shear. Measurements were performed at every 5°C starting from 30°C up to 50°C with a rheometer of the cone-and-plate type in the range of rate of shear 1×10−4∼10−2 sec−1. Measured results included behaviors characteristic of high rates of shear such as stress overshoot as well as those characteristic of low rates of shear. The accuracy of data as examined with linear viscoelasticity relations at low rates of shear was satisfactory. A method of reduced variables with respect to temperature T, time t, and rate of shear κ was revealed to apply to stress development function η(t, κ) and stress decay function η(t, κ): η(t, κ)/η0 and η(t, κ)/η0 and obtained at various temperatures were unique functions of two variables t/aT and κaT, where η0 is the zero-shear viscosity and aT is the shift factor usually employed in the time—temperature reduction for functions in linear viscoelasticity.