Preparation And Application Of Superhydrophobic Porous Ultrahigh Molecular Weight Polyethylene

Oil-water mixtures are created due to the frequent occurrence of oil spillage and continuous discharge of oily industrial wastewater.As a result,they are causing severe waste of resources,environmental pollution,and economic losses.Recently,absorption oil-water separation materials with superhydrophobic surfaces have shown great application potential.However,there are still many problems,such as expensive manufacturing costs,poor absorption efficiency,and second pollution to the environment,posing a nontrivial hurdle for practical oil-water separation.Moreover,using low-cost polymer materials such as polyethene,large-scale producing oil-water separation materials still have significant challenges.Therefore,various processing methods were proposed to prepare superhydrophobic oil-water separation materials.Also,the basic principle and application performance of the selective oil-water separation were studied.(1)Porous open-cell UHMWPE foams were prepared via supercritical CO₂gas foaming,and SiO₂nanoparticles modified were introduced into the UHMWPE matrix to improve the hydrophobic properties of the foams.The introduction of m-SiO₂nanoparticles significantly lowered the surface energy of the foams,improving the crystallinity of UHMWPE.In addition,it is prone to construct a multi-layered micro-nano structure on the surface of the foam,which improved the hydrophobicity of UHMWPE porous foam to a large extent.As a result,the water contact angle increased from 144.9°of the neat UHMWPE foams to 158.2°of the UHMWPE/m-SiO₂foams.The superhydrophobic foam has selective oil absorption capability;it can quickly absorb light oil and heavy oil from water and remain hydrophobic after absorption.Oil absorption capability ranges from 3.3 to 7.4 g/g,and the absorbed oils can be entirely removed by distillation.(2)Although the introduction of m-SiO₂nanoparticles can significantly improve the hydrophobicity of UHMWPE foam,it will increase the density of the foam and limit the oil absorption capability.A new method is proposed to prepare superhydrophobic UHMWPE foams.A superhydrophobic porous foam is prepared by etching the amorphous area on the surface of UHMWPE and deposition of hydrophobic m-SiO₂nanoparticles on the surface.The contact Angle of the material increased to 160.2°.Toluene can etch the amorphous region on the surface of UHMWPE foam,exposing the crystal region with multi-layered micro-nano structures and m-SiO₂attached to the surface of UHMWPE foam lowered the surface energy of the foam,which significantly improves the hydrophobic performance of the foam.The oil absorption capability of the foam is 2.7-7.2 g/g,and the absorbed oils can be entirely removed through distillation.In addition,the foam can separate oil from the oil-water mixture through pumping,and the separation efficiency is higher than 99%within 10cycles.(3)Given the defects of high density and a low oil absorption of UHMWPE foam prepared by supercritical CO₂foaming.This chapter will discuss a new technique for coating UHMWPE superhydrophobic films on the commercial foam surface.The coating layer is composed of shish-kebab structured porous UHMWPE film fabricated from a UHMWPE/xylene solution by shear flow-induced crystallization.The formed shish-kebab crystallites endow the sponge with excellent superhydrophobicity(WCA>150°).Besides,the developed sponge(UCS)exhibited a high absorption capability of 70?191 g/g for various oils and solvents,attributing to the low density and high porosity.The UCS can be assembled into small devices to selectively collect oil from open water and 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.