Selective dispersion of styrene-butadiene cross-linked waste in the polystyrene matrix: a transmission electron microscopy (TEM) research

Abstract

The aim of this study was to observe the morphological development in polystyrene (PS) non-reactive blends with a recycled styrene-butadiene compound (SBRr), using the styrene-butadiene-styrene (SBS) copolymer as a compatibilizing agent. The effect of different mixing sequences in the preparation of PS/SBRr/SBS (47.5/47.5/5 wt %) blends on the morphology were investigated. The blends were prepared in a co-rotating twin-screw extruder and molded via injection. The samples analyzed were taken from the Izod impact test specimens, subsequently prepared using cryo-ultramicrotomy, and observed through transmission electron microscopy (TEM). The blend prepared by the simultaneous mixing of all components in a single extrusion has a morphology with elongated particles. When the PS and SBRr were pre-mixed in the first extrusion before incorporating SBS in the second extrusion, the morphology exhibited a co-continuity tendency in the SBRr phase. On the other hand, when the PS premix is performed together with the SBS initially in the first extrusion prior to the incorporation of the SBRr into the second extrusion, the morphology is apparently more stable, with smaller particles, which are better distributed in the PS matrix. Therefore, the results show that, depending on the processing route, the morphology changes significantly.