Linear low-density polyethylene/high-density polyethylene blends: Effect of high-density polyethylene content on die swell and flow instability

This work aimed to evaluate the effect of high-density polyethylene (HDPE) content and of shear rate on the die swell and flow instability of linear low-density polyethylene (LLDPE)/HDPE blends. The results showed that the die swell of the LLDPE/HDPE blends increased with the increase in the shear rate. At high shear rates, the increase in the HDPE content led to an increase in the die swell of LLDPE/HDPE blends. The surface morphology analysis of the extrudates by optical and scanning electron microscopy revealed the presence of sharkskin and stick–slip flow instabilities in LLDPE and LLDPE/HDPE blends at the shear rates investigated. These instabilities were attenuated with the addition of HDPE and almost disappeared in the LLDPE/HDPE blend containing 50 wt% of HDPE. © 2020 Wiley Periodicals LLC