Multifunctional and fluorine-free superhydrophobic composite coating based on PDMS modified MWCNTs/ZnO with self-cleaning, oil-water separation, and flame retardant properties

We introduce a simple, fluorine-free, inexpensive route to fabricate a stable superhydrophobic coating comprising Multi-walled carbon nanotubes (MWCNTs)/ZnO composite modified with Polydimethylsiloxane (PDMS). The MWCNTs/ZnO composite was prepared by a sol-gel method. The composite coating can be applied on various substrates using a simple dip-coating method to achieve superhydrophobicity. The wettability of composite coating was investigated by adjusting MWCNTs loading in the composite solution. The result indicates that 2.5 wt. % of MWCNTs in the PDMS modified MWCNTs/ZnO composite displayed excellent superhydrophobic property with a water contact angle of 156 degrees and a sliding angle of 4 degrees. The coating was applied onto the copper mesh to separate oil-water mixtures because of its unique superhydrophobic and superoleophilic property and shows the high efficiency of separation of over 95 % for different oils with outstanding reusability. Furthermore, coating shows excellent self-cleaning, anti-fouling properties and retained its superhydrophobicity against strong acidic/alkaline solutions, corrosive medium, and demonstrated long-term durability in the ambient environment. Importantly, the coating also displayed excellent flame retardant performance compared to the uncoated surface and still exhibited its water repellency property after combustion. The proposed facile, cost-effective and environmentally friendly technique can provide a new tool to design durable and scalable superhydrophobic materials with special properties in the near future.