Phase morphological study on SEBS compatibilized PS/LDPE blends

• Main Authors: Chatchai Kunyawut, Julia S. Higgins
• Format: Article
• Language: English
• Published: Khon Kaen University 2014-09-01
• Series: KKU Engineering Journal
• Subjects: Block copolymer; Co-continuous morphology; LDPE; PS; SEBS
• Online Access: https://www.tci-thaijo.org/index.php/kkuenj/article/download/22549/19298

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