Preparation and characterization of carnauba wax-based particle with hierarchical structure and its use as hydrophobic coating for chitosan films

To improve the hydrophobicity of polysaccharide-based films, hydrophobic carnauba wax-based particles were prepared by Pickering emulsion. The influence of the different size of the particles on the structure and hydrophobicity of the chitosan coating films were investigated. The results showed that micro-scale particles (average particle size 25.04 μm) with nano-scale (5-10 nm) TiO2 uniformly distributed on the surface of the particles were formed by Pickering emulsion. The chitosan coating films showed higher contact angle and lower sliding angle compared to the control due to the hierarchical structure, hydrophobicity and arrangement of the particles. In addition, the small particle (23-48 μm) coating film showed higher hydrophobicity than the large particle coating film (48-70 μm) due to the small particle size and the formation of more small gaps. The gaps were conducive to form "air cushion" which reduced the contact area between water and the coating films and thus increased contact angle and decreased sliding angle. The coating films showed high chemical stability and low residual rates of liquid food. The results suggest that Pickering emulsion is an effective method to create wax-based particles with hierarchical structure and the particles have potential to be used as hydrophobic coating materials.