Phase morphological study on SEBS compatibilized PS/LDPE blends

摘要

The co-continuous phase morphology of polystyrene (PS)/low density polyethylene (LDPE) blendscompatibilized with poly(styrene-block-ethylene/butylene-block-styrene) triblock copolymers (SEBS) withvarying molecular weights has been investigated. The blend samples were prepared in amini-twin screw extruder. The barrel length and diameter are 224 and 16 mm, respectively. The diameter ofthe capillary die is 1 mm. The concentration of the blends was 70/30 wt% of PS/LDPE while that of the SEBSused was 5 wt% of the blend. The mixing temperatures used were 180, 250, and 280oC, and a screw speedof 60 rpm. The morphology of the blends was investigated using an AFM technique. Average dropletdiameters of the blend samples were determined using an OM technique. The co-continuous morphologyhas not been obtained in all the blends, although the mixing temperature used is as high as 280oC. Theexperimental results indicated that the model prediction of the co-continuous morphology proposed byWillemse and co-worker was not applicable to the blend systems studied. Only droplet-type dispersion wasobserved. This is considered to arise from the processing conditions and the mixing device used. The blendcompatibilized with the high molecular weight SEBS had higher dispersed phase size than that of the blendcompatibilized with the medium and low molecular weight SEBSs. This behaviour is likely to arise fromcoalescence during melt processing.