Structure-Properties Relationship of Commercial Ethylene/1-octene Copolymers from Chain-Shuttling Polymerization

Several commercial grades of ethylene/1-octene copolymers, INFUSE® by DOW Chemical Company, synthetized by chain-shuttling method, have been studied with different techniques, in order to develop structure-property relationships in the olefin multiblock copolymers. Commercial copolymers have been fractioned. Unfractioned and fractioned samples were analyzed in order to determine their comonomer content, molecular weight and molecular weight distribution. The structure and mechanical properties of these copolymers have been determined and have been correlated to the mechanical properties and the elastomeric behavior. All unfractioned samples show outstanding mechanical properties at 25 °C. Remarkable differences in the tensile properties of the block copolymers INFUSE occur by stretching at temperatures higher than 25°C. The elastic performances of ether-insoluble (Eti) fractions are similar to those of the corresponding unfractioned samples. The structural analysis for these samples suggests a microphase separated structure which consists of hard domains embedded in the amorphous matrix of soft blocks. Furthermore, the samples that form an interpenetrating network crystallize more slowly (at low temperatures) and show higher mechanical strength and ductility even at high temperatures. The samples with no inter-woven structure instead, form a more heterogeneous morphology, and loose large part of mechanical strength already at 60 ° C.