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 compatibilize d with a (styrene-ethylene/butylene-styrene) tri-block copolymer (SEBS). Bo th uncompatibilized and compatibilized HDPE/PS 80/20 blend specimens were p repared in a twin-screw extruder followed by injection molding. The effect of SEBS content on the tensile properties of the blends was investigated. I t was found that the modulus and yield stress of the HDPE/PS 80/20 blend te nd to decrease with increasing SEBS content. However. the elongation at bre ak of the blend improved significantly with the addition of SEBS, indicatin g the effectiveness of compatibilizing effect of a tri-block copolymer in t he immiscible HDPE/PS system. Scanning electron microscopy examination show ed 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 effectivel y. The fracture toughness of the blends was evaluated by the essential work concept. The result showed that the essential work of the compatibilized H DPE/PS blends also increases with increasing SEBS content.