Fabrication of superhydrophobic coatings with edible materials for super-repelling non-Newtonian liquid foods

Abstract

Superhydrophobic coatings were fabricated with edible candelilla wax and rice bran wax via one step spraying a wax-in-ethanol hot solution on polypropylene (PP) substrates for food containers. Beautiful “flower-like” surface microstructures were formed only by self-roughening of the coating without adding any nanomaterials or any lithography step, making the coatings display great superhydrophobicity for a variety of non-Newtonian viscous liquids with contact angles higher than 150° and sliding angles close to 0°. The as-coated PP can keep excellent superhydrophobic properties after impact from hot aqueous solution (about 70 °C) or 1200 repeated bends, exhibiting good heat resistance and superior flexibility. Importantly, the excellent durability could make it super-repel non-Newtonian fluids after various types of damage (including finger touching and multiple abrasion cycles with sandpaper). This approach can be applied to the inner surface of all kinds of food packaging to reduce liquid food residue.