Effects of block architecture on structure and mechanical properties of olefin block copolymers under uniaxial deformation

Effects of block architecture on structure and mechanical properties of olefin block copolymers (OBC) under uniaxial deformation were studied. The two chosen OBCs, OBC-LS and OBC-HS, were ethylene-octene block copolymers. Molecular weight was measured by high-temperature gel permeation chromatography in 1,2,4-trichlorobenzene using polystyrene standards and was converted to polyethylene equivalents. The overall and hard block octene contents were determined by ¹³C NMR, while the soft block octene content was determined by ¹H NMR on material extracted from pellet samples dissolved in n-hexane. Melting temperature was measured by DSC using a 10°C/min heating rate, and crystallinity was obtained by comparison to the theoretical heat of fusion of 100% crystalline polyethylene. As strain increases to about 12 before fracture, an intense pointlike diffraction pattern, resulting from highly orientated monoclinic crystals is seen on the equator.