POLYSTYRENE HIGH DENSITY POLYETHYLENE BLENDS COMPATIBILIZED BY TRI-BLOCK COPOLYMER II - TOUGHENING AND DEFORMATION MECHANISMS/

A dilatometry method was applied to study the tensile deformation mech anisms of polystyrene/high density polyethylene (80/20) blends compati bilized by different amounts of a styrene-ethylene-butylene-styrene tr i-block copolymer (SEBS). The volume change of the sample during uniax ial tensile process, which was determined by two extensometers, was fo und to be related to the various modes of deformation. To obtain quant itative 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 tensi le behaviors of the pure polystyrene and high density polyethylene wer e investigated also. The results indicated that elastic deformation wa s the main deformation mode for pure polystyrene and the uncompatibili zed 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% SEES, the deformation process was very complex, craz ing and shearing predominated alternatively in different ranges of str ain. However, shearing was the main non-Hookean deformation mechanism for the blends containing SEES content higher than 4 wt%. The differen t deformation characteristics of the blends were related to their morp hologies.