TAILORING THE TENSILE PROPERTIES OF OLEFIN BLOCK COPOLYMER ELASTOMER BY HIGH DENSITY POLYETHYLENE

The effect of high density polyethylene (HDPE) on the crystallization and tensile behavior of the olefin block copolymer (OBC)-rich blends was examined. Morphological studies revealed that the two components were phase separated in the melt state. Partial miscibility between the two components came from the "phase mixing", which was attributed to the randomness of the block distribution produced by chain shuttling polymerization. Cocrystallization of HDPE and OBC was observed in slow cooling samples. Crystalline lamellae originating from the HDPE-rich phase passed through the OBC-rich phase and organized into spherulites in a space-filling manner. With increasing HDPE fraction, the modulus and tensile strength of the blends increased gradually. Meanwhile, high fracture strain and excellent strain recovery were retained. The stress-strain curves of the elastomeric blends could be nicely described by the Slip-link model. The crystalline part in blends provided the physical basis for "sliplinks",while the tightened topological entanglements served as crosslinks". The density of sliplinks and crosslinks increased with increasing HDPE content. The increased crystallinity was shown to be the reason for the increased sliplinks number. By analyzing changes of microstructure imparted by HDPE, the structure property correlation was nicely established. It was clearly demonstrated that HDPE could effectively tailor the tensile properties of OBC by simple blending approach.