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Although polypropylene (PP) foams fabricated by microcellular injection molding (MIM) have been widely studied and globally applied, it is still a big challenge to achieve lightweight products with high mechanical performance. Herein, the MIM method assisted by a fast cooling design was applied to prepare lightweight bimodal nanoporous PP foams with high toughness. A specific mold with a thin cavity was designed to achieve rapid cooling rate during MIM process, and to further accelerate crystallization and refine crystals, which was verified by visualization results, DSC curves, and WAXD patterns. Thus, nanocellular PP foams were prepared, whose high toughness was presented in tensile testing, especially for bimodal cellular foams, more than 327% higher than that of microcellular foams, and up to 53% higher than that of solid. It is owing to the introduced matrix craze, shear yielding, and larger plastic zone by nanocells and the transformed crack propagation direction by microcells. Therefore, this novel toughening method paves a promising prospect for MIM technology to achieve lightweight and tough products for industrial applications. Unlabelled Image • High-tough and lightweight PP/talc bimodal nanoporous foams were fabricated by microcellular injection molding. • Fast cooling pronouncedly enhanced crystallization and contributed to formation of nanocells. • Bimodal cells significantly toughened PP composite foams by changing crack propagation direction. [ABSTRACT FROM AUTHOR]

Water pollution caused by industrial oily wastewater, is world-widely concerned by both scientific and practical researches, owing to its catastrophic destruction to natural environment, which highlights the urgency of producing green and advanced separation materials. Herein, a novel approach was proposed to fabricate oil-absorbing and oil/water-separating microcellular polypropylene (PP)/carbon nanotubes (CNTs)/sorbitol nanocomposites using a simple, green, and facile microcellular foaming technology. Owning to the effectively modified crystallization via introducing CNTs/sorbitol derivatives, the ultralight and highly-reticulated PP microcellular foam was prepared with an open-cell content of 99.4% and an expansion ratio of 50, which facilitated the creation of nano-porous structures on cell walls. Hence, the as-prepared PP nanocomposite foam presented pronounced absorption capacity of 40 g/g for applied oils with recovery efficiency of 97.2%, superior thermal-insulating and mechanical performance. Furthermore, the as-achieved unique hierarchical porous structures of the PP/CNT/sorbitol foam contributed to the outstanding oil/water separation capability, separation efficiency of up-to 97.6%, ascribed to its superhydrophobicity, capillary penetration action, high porosity and open-cell content. Therefore, this work provided new insight into the feasibility of advantageous, high-efficiency, environmentally friendly, and profitable PP-based foams as oil absorbents, which, to the best of our knowledge, outperform conventional polymer absorbents in treatment of oily wastewater. [Display omitted] • Superlight PP/CNT/sorbitol foams with high open-cell content were prepared by microcellular foaming. • Undifferentiated absorption capacities of more than 40 g/g for 10 kinds of oil were achieved by PP/CNT/sorbitol foams. • PP/CNT/sorbitol foams showed outstanding oil/water separation efficiencies, up to 97.6%. • PP/CNT/sorbitol foams exhibited thermal conductivity as low as 28.18 mW∙m-1∙K-1 with advanced compressive strength. [ABSTRACT FROM AUTHOR]