Polystyrene/High Density Polyethylene Blends Compatibilized by Tri-Block Copolymer II. Toughening and Deformation Mechanisms

Abstract

A dilatometry method was applied to study the tensile deformation mechanisms of polystyrene/high density polyethylene (80/20) blends compatibilized by different amounts of a styrene-thylene-butylene-styrene tri-block copolymer (SEBS). The volume change of the sample during uniaxial tensile process, which was determined by two extensometers, was found to be related to the various modes of deformation. To obtain quantitative information on the separate contributions of several possible deformation modes to the total deformation, a simple model proposed by Dekkers and Heikens was used in this study. For comparison, the tensile behaviors of the pure polystyrene and high density polyethylene were investigated also. The results indicated that elastic deformation was the main deformation mode for pure polystyrene and the uncompatibilized blend; whereas, plastic deformation was found to play an important role in a tensile process of the compatibilized blends. For the blend containing 2 wt% SEBS, the deformation process was very complex, crazing and shearing predominated alternatively in different ranges of strain. However, shearing was the main non-Hookean deformation mechanism for the blends containing SEBS content higher than 4 wt%. The different deformation characteristics of the blends were related to their morphologies.