High-performance low-cost superhydrophobic sponges are desired for selective recycling of leaking oils from open water. Herein, an ingenious method is proposed to fabricate an ultrathin superhydrophobic coating layer on a commercial sponge. The coating layer is composed of a shish−kebab-structured porous ultrahigh molecular weight polyethylene (UHMWPE) film that is fabricated from a UHMWPE/xylene solution by shear flow-induced crystallization. A strong relationship between the shish−kebab crystallite morphology and the superwetting performance is confirmed. The UHMWPE coating layer fabricated at a 900 rpm rotation rate possesses a lamellae size of 95.1 nm and a lamellae distance of 27.4 nm, which lead to a high water contact angle of 157°and a low contact angle hysteresis of 4.5°. The UHMWPE layer prepared in 4 min of treatment is thick enough to prevent the intrusion of water even under vacuum and remain superoleophilic. The developed UHMWPE-coated sponge (UCS) exhibited a high absorption capability of 70−191 g/g toward various oils and solvents, which is comparable with the neat melamine sponge. Its excellent compressibility and durability enabled fast recovery of absorbed oil with a high recovery rate (over 85%) by mechanical squeezing. The UCS could be assembled into small devices to selectively collect oil from open water and a water/oil mixture using a pump, which manifests its promising practical applicability. Apart from these extraordinary properties, the approach developed has the lowest material cost and the shortest processing time hitherto.

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The low durability and stability of superhydrophobic foams and high fabrication costs are the main reasons that limit their practical applications in water remediation and oil recycling. Herein, an extremely superhydrophobic and exceptionally robust foam was developed based on ultrahigh-molecular weight polyethylene (UHMWPE) by supercritical carbon dioxide (scCO2) foaming and subsequent surface modification. The developed foam comprises a highly porous structure decorated with hydrophobic silica nanoparticles and aligned UHMWPE crystallites, constructing a complex micro–nanosized hierarchical morphology, which contributed to an unprecedented water contact angle (WCA) of 162° and a sliding angle of 1°. When used in selective oil absorption and oil/water separation, the foam demonstrated about 100% separation efficiency in repetitive use and even under a vacuum of −70 Kpa due to its high water repellency. More importantly, the foam has outstanding tolerance against mechanical damages such as ultrasonication, bending and twisting, tape peeling, steel wool abrasion, and knife scratching. The surface could maintain the hierarchical structure and a WCA of over 156° after enduring different damages. Moreover, when the surface is clogged, the foam could restore its superhydrophobicity by arbitrary fracturing and cutting, resulting in a theoretically unlimited lifespan. This work not only proposes a UHMWPE-based superhydrophobic foam with extremely high superhydrophobicity, durability, and separation efficiency but also provides insights into the design and mass production of ultraefficient and robust superhydrophobic porous materials for practical applications.

Polypropylene/carbon black (PP/CB) and PP/CB/multiwalled carbon nanotube (PP/CB/MWCNT) composites were fabricated by solid and foam injection molding, with the goal of enhancing the electrical conductivity of the composites while decreasing the cost of the final product. The foaming behavior and through-plane (T-P) electrical conductivity of the composites were characterized and analyzed. Cell growth increased the interconnection of the conductive fillers, changed the filler orientation, and enhanced the T-P electrical conductivity of the composites. Under appropriate processing conditions (200°C melt temperature, 70 cm3/s injection flow rate, and 5% void fraction), the T-P electrical conductivity of the foam PP/CB composites was 5 orders of magnitude higher than that of the solid composites (from 5.877 × 10−12 S/m to 1.010 × 10−7 S/m). Moreover, the T-P electrical conductivity values of the PP/CB and PP/CB/MWCNT were compared at the same conductive fillers content (15 wt%). The results showed that the T-P electrical conductivity of the PP/CB/MWCNT composites was far higher than that of the PP/CB composites by almost five orders of magnitude because the MWCNT acted as a bridge between CB particles, and a unique geometric shape was formed in the system. The T-P electrical conductivity of the foam PP/CB/MWCNT composites with 15 wt% carbon fillers was higher than that of the solid PP/CB composites with 20 wt% carbon fillers. This study reveals that the effect of foaming and the addition of hybrid fillers can improve the T-P electrical conductivity of plastic products, which is very important for the development of lightweight conductive plastics.

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