Polypropylene Composites with Ultrahigh Low-Temperature Toughness by Tuning the Phase Morphology

To broaden the potential application of isotactic polypropylene (iPP) in low-temperature conditions, iPP/0.1 wt % β-nucleated agent/30 wt % ethylene–octene multiblock copolymer (iPP/0.1 wt % β-NAs/30 wt % olefin block copolymer (OBC)) blends were endowed with ultrahigh low-temperature impact toughness by adjusting the nanotube (CNT) content. In comparison with pure iPP, the low-temperature impact toughness of iPP/0.1 wt % β-NAs/30 wt % OBC composites with only the addition of 0.5 wt % CNTs reached as high as 52.2 kJ/m2 at −20 °C, of which the increment of impact strength was about 2386%. This optimum content of CNTs gave rise to a co-continuous phase morphology in β-nucleated iPP composites, which turned out to be the key to greatly enhanced stress dissipation, even in a low-temperature environment. In addition, the distribution of CNTs between iPP and OBC phase and the presence of self-toughened β-crystals that were induced by β-NAs and OBC contributed to improving the low-temperature impact strength of iPP-based composites. A feasible strategy is developed to substantially reinforce the low-temperature toughness of iPP-based composites, which expands their potential applications in industrial sectors.