Non‐Newtonian behavior in steady flow over the range from the lower to the upper Newtonian region for polystyrene solution

Graessley's entanglement theory of viscosity modified by a frictional viscosity parameter ηfric is applied to data on solutions of polystyrene in diethyl phthalate at various concentrations and different temperatures. All the data modified give a single master curve over the entire rates of shear, as obtained previously with polydimethyl‐siloxanes of various molecular weights and their solutions of various concentrations. The zero‐shear viscosity η0, the upper Newtonian viscosity η∞, and ηfric are compared. Three activation energies for flow are estimated from η0, η∞ and ηfric, and are compared. The result suggests that the flow behavior in the upper Newtonian region is much more dependent on ηfric than on the entanglement viscosity term ηent. The ratio of zero‐shear entanglement viscosity ηent,0 to ηfric can be used as a measure of the non‐Newtonian behavior of the present solutions. Non‐Newtonian behavior of the investigated polymer solution becomes appreciable at about ηent,0/ηfric = 2.5. These results are in agreement with previous conclusions based on comparison between η0, η∞ and ηfric for polydimethyl‐siloxanes and their solutions.