The melt elastic behavior of polypropylene/glass bead composites in capillary flow

Abstract

The melt extrudate swell and entry pressure losses are important characteristics of elastic properties during die extrusion of polymeric fluids. They are usually expressed with die-swell ratio ( B) and entry pressure drop (Δ P o). In the present paper, the die-swell behavior and entrance pressure drop of a polypropylene (PP) filled with A-glass beads were investigated by using a Rosand capillary rheometer to identify the effects of the filler contents and extrusion rate on the elastic behavior of the sample melts. The experiments were carried out under the conditions with an apparent shear rate range of 50–10 4 s −1 and a temperature of 190 °C. The results showed that B increased nonlinearly with increasing shear rate at the wall ( γ w), and increased linearly with the increase of shear stress at the wall ( τ w). With the increase of the volume fraction of the fillers B decreased nonlinearly. Similarly, the entry pressure drop increased linearly with the increase of τ w, whereas the influence of the filler concentration on Δ P o was insignificant in this case. Furthermore, B increased as a linear function of Δ P o, and extension stress ( σ e) increased nonlinearly with increasing γ w.