Shear Induced Pressure Determines a Reduction in Polymer Radius

TL;DR

This paper demonstrates that shear induced particle pressure causes polymer chains to compress, leading to reduced polymer size and viscosity at higher shear rates, aligning with experimental observations.

Contribution

It introduces the concept of shear induced particle pressure into polymer rheology, predicting shear-dependent polymer compression and viscosity reduction.

Findings

Polymer blob size decreases with shear rate.

Viscosity follows a power law with shear rate.

Different concentration regimes show varying power law behaviors.

Abstract

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.