  Shear induced particle pressure has been measured and modelled for
concentrated suspensions of particles. Importantly, the significance of the
shear induced particle pressure has not been recognized in polymer rheology.
The shear induced particle pressure results in an inward pressure on the
polymer chains resulting in a shear dependent compressive force. The analytical
form of the force balance equations that incorporate the effect of shear
induced particle pressure predict a reduced polymer blob size and reducing
viscosity with increasing shear rate as has been observed experimentally. Power
law behavior is found for the viscosity in accord with the general behavior
observed for the rheology of concentrated polymer solutions and melts.
Differing powers are found for the behavior depending on the concentration
regime.
