Morphological characterisation and dynamic rheology of nano-structured blends of polystyrene and SEBS

Polystyrene homopolymer (hPS) was melt-blended with styreneethylene/ butylene-styrene (SEBS) in a counter-rotating twin-screw extruder to produce hPS/SEBS blends. The morphology of the hPS/SEBS blends was investigated using environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM). The dynamic rheological behaviour of the blends was studied using a parallel plate rheometer. TEM and ESEM images of the hPS/SEBS blends showed three different morphologies at three different SEBS concentration ranges. When SEBS concentration was less than 30 wt%, the hPS-rich blends hPS/SEBS 90/10 and 80/20 showed a droplet/matrix morphology. When SEBS concentration was between 30 and 70 wt%, the blend morphology revealed a co-continuous nano-structure. At SEBS concentrations 80 wt% and above, TEM images of the SEBS-rich blends showed that the homopolymer hPS was absorbed within the bulk of SEBS, resulting in a modification of its original microstructure. Dynamic rheological tests showed that the blend morphology had significant effect on their rheological behaviour at low frequencies.