Morphology evolution of polycarbonate-polystyrene blends during compounding

The morphology evolution of polycarbonate-polystyrene (PC/PS) blends during the compounding process in three blending methods of industrial relevance, namely melt blending, re-melt blending in a twin-screw extruder and tri-melt blending in an injection-moulding machine, was investigated using scanning electron microscopy (SEM) Co examine nine blend compositions. Blends were prepared at compositions where phase inversion was expected to occur according to model predictions. The experimental results were compared to the values of the point of phase inversion calculated with the semi-empirical model. The results show that the formation of co-continuous morphology strongly depends on blend composition and melt blending method, whereas the model prediction for phase inversion deviates from the experimental values. Further, we found that the initial mechanism of morphology evolution involves the formation of blades or stratifications in the continuous phase. These blades or stratifications became unstable due to the effects of Bow and interfacial forces. We also found that fibre formation in the dispersed phase was favoured by higher shear rate. (C) 2001 Elsevier Science Ltd. All rights reserved.