Deformation mechanisms and fracture toughness of polystyrene/high-density polyethylene blends compatibilized by triblock copolymer

A dilatometric technique was used to explore the tensile deformation mechan isms of polystyrene (PS)/high-density polyethylene (HDPE) blends compatibil ized by a styrene-ethylene-butylene-styrene (SEBS) triblock copolymer. The volume change of the sample during a uniaxial tensile process was determine d with two extensometers, and it provided useful information concerning the tensile deformation mechanism. A simple model was used in this study in or der to obtain quantitative information on the separate contributions of sev eral possible deformation modes to the total deformation. The results indic ated that elastic deformation was the main deformation mode for PS. However , elastic deformation was the main mode of deformation prior to yielding fo r SEES compatibilized PS/HDPE blends; thereafter the plastic deformations ( including shear and crazing) appeared to dominate over the elastic deformat ion. Moreover, crazing was the main plastic deformation mode for the blend containing 20 wt % HDPE, and shear deformation became predominant when the HDPE content was further increased. Finally, the essential work concept was used to determine the fracture toughness of the typical ductile PS/HDPE/SE BS 10/80/10 blends. (C) 2000 John Wiley & Sons, Inc.