Carbon nanotubes induced brittle-ductile transition behavior of the polypropylene/ethylene-propylene-diene terpolymer blends

Brittle-ductile transition is a well-known phenomenon in the elastomer-toughened polymer blends, and it is usually used to value the toughening efficiency of the elastomers. In this work, a small quantity of carbon nanotubes (CNTs) were introduced into the polypropylene/ethylene-propylene-diene terpolymer (PP/EPDM) blends to investigate the effect of CNTs on the brittle-ductile transition of the blends. The mechanical properties, morphologies and the crystallization behaviors of samples were comparatively investigated. The results showed that CNTs not only enhanced the impact strength of the materials but also promoted the occurrence of brittle-ductile transition at relatively low EPDM content. The crystallization and melting behaviors of PP matrix were not apparently influenced by CNTs, which could be attributed to the selective localization of CNTs in the EPDM component. Further results demonstrated that the toughening efficiency of CNTs in the blend composites was dependent upon the matrix ligament thickness (τ), and there was an appropriate range of τ (0.85-1.15 μm), at which CNTs exhibited high toughening efficiency. This work provides new insight on the toughening effect of CNTs in the immiscible polymer blends.