Effect of Compatibilizer Content on the Tensile Properties and Fracture Toughness of High Density Polyethylene/Polystyrene Blends

High-density polyethylene (HDPE)/polystyrene (PS) blends were compatibilized with a (styrene-ethylene/butylene-styrene) tri-block copolymer (SEBS). Both uncompatibilized and compatibilized HDPE/PS 80/20 blend specimens were prepared in a twin-screw extruder followed by injection molding. The effect of SEBS content on the tensile properties of the blends was investigated. It was found that the modulus and yield stress of the HDPE/PS 80/20 blend tend to decrease with increasing SEBS content. However, the elongation at break of the blend improved significantly with the addition of SEBS, indicating the effectiveness of compatibilizing effect of a tri-block copolymer in the immiscible HDPE/PS system. Scanning electron microscopy examination showed that PS phase is fibrillated in the matrix as long fibers, and the SEBS copolymer addition appears to reduce the domain size of PS phase effectively. The fracture toughness of the blends was evaluated by the essential work concept. The result showed that the essential work of the compatibilized HDPE/PS blends also increases with increasing SEBS content.