Melt Elongation Flow Behavior of Low-Density Polyethylene Composites Filled with Nanoscale Zinc Oxide

The melt elongation flow properties of low-density polyethylene/nanoscale zinc oxide (nano-ZnO) composites were studied using a Rheotens rheometer (Göttfert Werkstoff-Prüfmaschinen GmbH, Buchen, Germany). The die extrusion rate varied from 9 to 36 mm/s, the temperature ranged from 160°C to 200°C, and the nano-ZnO weight fraction range was from 0.2 to 4 weight percent (wt.%). The results showed that the melt elongation stress increased with the increasing elongation strain rate; the melt elongation viscosity decreased with the increasing temperature, and the temperature dependence obeyed the Arrhenius equation. The melt elongation viscosity of the composites with 0.4–0.8 wt.% nano-ZnO was lower in the whole composite system. Moreover, the melt elongation viscosity increased when the elongation strain rate was lower than 0.3 s⁻¹ and then decreased with the increasing elongation strain rate; the melt elongation viscosity reached a maximum at an elongation strain rate around 0.3 s⁻¹ and presented the stress hardening phenomenon.