Steady-State Melt Flow Behavior of Polyethylene Blends

Abstract

The steady-state melt flow behavior covering six decades of shear rate was studied for various types of polyethylene and their blends. Two instruments were used. The Kepe's cone and plate consistometer measures viscosities at low shear rate at the range from 10−2 to 1 sec−1. A gas-driven capillary viscometer gives high shear data. The shear stress at the capillary wall was calculated by the method proposed by Bagley and the shear rate at the wall was obtained after Robinowitsch. A special effort was made to observe the change in low shear flow behavior of a resin due to an addition of gels, high ends or low ends of molecular weight distribution. Addition of low ends up to 20% does not alter the “shape” of the viscosity shear rate flow curve appreciably. But with an addition of high ends, the “shape” of the flow curve changes considerably. With an addition of gels, the flow curve at low shear rises rapidly as shear rate decreases. An inflection was observed followed by a “tail-up” at the low shear range.