Rheological Behavior of Immiscible PS/LDPE Blends: A Comparative Study of the Palierne Emulsion Model

Abstract

The rheological behavior of polystyrene (PS)/low density polyethylene (LDPE) blends have been investigated. Blends with 10, 20 and 30 wt% LDPE were prepared using a co-rotating twin-screw extruder at a melt mixing temperature of 180°C. SEM micrographs revealed that all blends exhibited droplet-type dispersion morphology. Rheological measurements were performed at the same temperature as the mixing temperature. The complex viscosity of the blends laid between those of the PS and the LDPE and decreased with increasing LDPE concentration. The plots of tand of blends with 10 and 20 wt% LDPE suggested that the elasticity of these blends was comparable to that of the pure PS. By contrast, the elasticity behavior of the blend with 30 wt% LDPE was shown to be similar to that of LDPE. Palierne model predictions were in very good agreement with the experimental data for the blends having 10 and 20 wt% LDPE. For the 30 wt% LDPE blend, agreement with the prediction and the experimental data was not as good. Within the frequency range of the rheological measurements, the second plateau at low frequency which results from an increase of the elasticity was not observed in any of the blends studied. This is expected to be due to the long relaxation times of the relatively large LDPE droplets of these blends. doi: 10.14456/WJST.2015.97