Measurement of the high rate flow properties of filled HDPE melts by capillary rheometer: Effects of the test geometry

Capillary rheometry was used for measurement of the high rate steady-state flow properties of micro-filled high- density polyethylene (HDPE) melts, and the effects of the test geometry were investigated. Attention was paid to the influence of the die diameter. The micro-compounds examined had the same filler content (10 vol.% in the melt state), but differed in the nature and geometry of filler (glass beads, discontinuous glass fibres and talc).
A die diameter effect on the pressure drop localized at the die entrance was clearly observed for the unfilled HDPE; for the micro-filled melts, this effect was either enhanced or considerably reduced, depending on the type of filler (opposite effects were induced by glass beads and by glass fibres). A die diameter effect on the macroscopic shear viscosity response was noticed only for the melts filled with particles with relatively high aspect ratio (glass fibres and talc platelets).