Method to prepare superhydrophobic sheets from virgin and waste polypropylene

A method of making a superhydrophobic sheet, the method comprising:

• dissolving polypropylene (PP) isolated from plastic waste in a solvent to form a clear polypropylene solution;
• pre-heating a solid substrate to a temperature below a boiling point of the solvent;
• applying a portion of the clear polypropylene solution onto the solid substrate and drying the solvent from the polypropylene solution using vacuum or air to obtain a porous base layer
• annealing the porous base layer at a temperature above the melting point of polypropylene for a specific period of time to obtain a non-porous base layer;
• applying a top layer comprising a heated portion of the clear polypropylene solution on the non-porous base layer while the non-porous base layer is hot;
• drying the solvent from the clear polypropylene solution forming the top layer using vacuum or air to provide a top layer having a contact angle ranging from 140 degrees to 160 degrees;
• and
• separating the top and base layers of polypropylene from the substrate to obtain a superhydrophobic sheet having a thickness ranging from about 10 μm to about 200 μm and a tensile strength ranging from about 5 MPa to about 70 MPa.