Superhydrophobic ultra-high molecular weight polyethylene nanocomposite foams fabricated by supercritical CO2 foaming for selective oil absorption

Superhydrophobic foams are promising substances for removing leaked oil from water. However, producing superhydrophobic foams with stable high performance using a low-cost, scalable, and environmentally friendly means is a challenge. Herein, superhydrophobic nanocomposite foams comprising of ultra-high molecular weight polyethylene (UHMWPE) and modified silica nanoparticles (NPs) were developed using melt blending and supercritical CO2 foaming. Long carbon chains grafted on silica NPs formed a shell with a thickness of 100 nm, which rendered the NPs hydrophobicity and generated entanglements with UHMWPE matrix. The optimum foam with an average cell size of 41.5 μm achieved a high water contact angle of 158.2 ± 1° and a low sliding angle of 1.7 ± 0.4°, attributing to the micro-nano hierarchical structure constructed by the porous structure and the modified NPs. The foam remained superoleophilic and demonstrated high efficiency in separating both light and heavy oils from water. A relatively high oil absorption capacity of 2.8 to 7.2 g/g was achieved towards various oils and solvents, and separation efficiency of over 99 % could be maintained after ten cycles of reuse. This work provides a facile and scalable method to produce superhydrophobic UHMWPE nanocomposite foams with stable high performance for effective oil absorption from water.