Comparison of Polypropylene Toughening With Olefin Block Copolymer and Polyolefin Elastomers

ABSTRACT

Polypropylene (PP) is a widely used commodity plastic, but its inherent brittleness below about 0°C limits its applications requiring high toughness. In this study, three polyolefin elastomers (ethylene/1‐octene random copolymer (POE‐8C), ethylene/1‐butene random copolymer (POE‐4C), and ethylene/1‐octene olefin block copolymer (OBC)) are systematically compared as PP toughening modifiers. The effects of comonomer type and chain sequence structure on mechanical properties, phase morphology, crystallization behavior, and rheological behavior are investigated. Compared with the random copolymer POEs, OBC exhibits superior toughening efficiency because OBC contains crystallizable hard segments and amorphous soft segments. In PP blends, OBC forms better and more uniform dispersed phases, whereas the POE particles are coarser. At 40 wt% loading, the impact toughness of the PP/OBC blends increases up to approximately 16 times, far exceeding that of the two POEs (about two times for POE‐8C, and even less for POE‐4C), while a tensile modulus of 296 MPa is retained. In addition, the toughening mechanism was also discussed in detail. This work reveals that chain‐segment sequence controls PP toughening efficiency through mesophase separation‐like domains, providing guidance for the elastomer design of PP materials with high toughness and high stiffness.