From waste plastic to artificial lotus leaf: Upcycling waste polypropylene to superhydrophobic spheres with hierarchical micro/nanostructure

Polypropylene (PP) is the second most commonly used plastic in the industry and a key component in materials packaging and medical consumables. Its accumulation has increased due to the shift from reusable to single-use containers and the significant amounts of biomedical waste generated. We are working towards developing a cost-efficient methodology to convert polypropylene (PP) waste into superhydrophobic materials. Our approach involves the chemical treatment of waste PP to create micron-sized spheres (5 ∼ 10 µm) with hierarchical nanostructures and superhydrophobic properties. The produced microspheres show a water contact angle up to 164° and a rolling off angle as low as 2.6°, comparable to natural lotus leaf. The effectiveness of this process has been demonstrated in waste PP from various sources, including surgical masks, syringes, take-away food boxes, and bubble tea cups. The resulting superhydrophobic material has promise for applications in superhydrophobic coating, self-cleaning, and water-oil separation.