An equation of state for non-Newtonian fluids

An equation of state for non-Newtonian fluids is suggested which should apply to polymer solutions and melts. It assumes that the polymer molecules form temporary crosslinks in solution and that the lifetimes of these crosslinks are stress-dependent. Irrespective of the form of the stress-dependence it is shown that a consequence of the equation of state is that p122 [is propostional to] p11 - p22 where pij (i, j = 1, 2, 3) are the components of the stress tensor in simple shear flow referred to the usual axes.