Shear rheological properties and extrusion of polystyrene/low-density polyethylene blends

The flow behavior of polystyrene/low-density polyethylene blends and parent polymers through three kinds geometry of capillary die was studied at 190°C by using a Brabender extruder and an Instron Capillary Rheometer. The melt viscosity data were corrected for pressure effect as well as the entrance/exit and non-Newtonian fluid effects. The effects of blends composition and shear stress on the flow curves, melt viscosity, die swell, melt fracture were investigated as well.; The blends' flow behavior was found to be different from that of the individual components. The embedment of less viscous of PS into LDPE matrix plays a significant lubricating role in the melt viscosity due to the flow mechanism of the interfacial slippage at lower shear region. The viscosities of all samples tend to converge over a certain critical shear rate that can be served as onset of shear-induced droplet breakup or the formation of the dispersed phase. After that, at high-shear-region, the effect of shear force on the dispersed-phase deformed droplets begins to control the consequent melt viscosity of different compositional blends to a close level. The most appropriate blending ratio of 50/50 that gives highest interfacial slippage between two unlike phase verified through a typical mathematical model for 2-phase system that suggest the formation of a co-continuous morphology providing economic advantage from a processability point of view.; The extents of die swell and melt fracture increase with shear stress. The shorter capillary die promotes forming the distorted extrudate. Both characteristics of blends tend to be analogous to those of matrix parent polymer. The co-continuous 50/50 PS/LDPE blend appears to exhibit a small extent of melt elasticity and extrudates instability.