Polymer Rheology

The plots in Fig. A below were produced from rheological measurements carried out on a commercial grade of polyethylene at 180C using a slit-die rheometer fitted with pressure transducers along the flow length of the die channel. The dimensions of the die channel were: Depth =1mm; Width =15mm; Length =20mm Verify whether the polymer melt obeys the power law relationship by calculating the power law index at each shear rate. (Note that the shear stress at the wall of the channel of a slit-die can be calculated by using the equation derived for a circular die, replacing the radius with depth.)