Effect of Octene Block Copolymer (OBC) and High-Density Polyethylene (HDPE) on Crystalline Morphology, Structure and Mechanical Properties of Octene Random Copolymer

Blending octene random copolymer (ORC) with other polymers is a promising approach to improving ORC mechanical properties, such as tensile strength and elongation. In this study, octene block copolymer (OBC) with lower density than ORC and high-density polyethylene (HDPE) were used to blend with ORC. The effect of both OBC and HDPE on ORC was analyzed using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and small-angle X-ray scattering (SAXS). For ORC/OBC blends, a small amount of OBC can improve the crystallization ability of ORC. Meanwhile, for ORC/HDPE blends, the crystallization ability of ORC was significantly suppressed, attributed to good compatibility between ORC and HDPE as indicated by the homogeneous morphology and the disappearance of the α transition peak of ORC in ORC/HDPE blends. Therefore, the tensile strength and elongation of ORC/HDPE blends are significantly higher than those of ORC/OBC blends. For ORC/OBC/HDPE ternary blends, we found that when ORC:OBC:HDPE are at a ratio of 70:15:15, cocrystallization is achieved. Although HDPE improves the compatibility of ORC and OBC, the three-phase structure of the ternary blends can be observed through SAXS when HDPE and OBC exceed 30 wt%. Blending HDPE and OBC (≤30 wt%) could improve the mechanical property of ORC.