Enhancing the Hydrophobicity of Chitosan Films Through Hierarchical Plant Wax Particles and Dilute Chitosan Solution Coatings

The strong hydrophilicity of chitosan-based films limits their practical applications. To enhance the hydrophobicity of these films, hierarchical carnauba wax particles were prepared using the Pickering emulsion method and subsequently coated onto the film surfaces. The wax was stabilized with various types and concentrations of TiO2. The resulting wax particles exhibited a micro-scale structure, with nano-scale TiO2 and micro-scale TiO2 aggregates present on the surface. No significant differences in contact angle were observed among these particles. Hydrophilic TiO2 demonstrated smaller sliding angles and particle sizes. To improve the mechanical durability and compatibility of the wax particles with the chitosan matrix, the wax particles were mixed with a diluted chitosan solution before coating. As the concentration of wax particles increased and the concentration of chitosan solution decreased, more wax particles became exposed on the surface. This exposure increased the roughness of the coatings, resulting in a significant increase in contact angle and a decrease in sliding angle. A high concentration of chitosan provided greater protection to wax particles during mechanical durability tests. Additionally, the residue rate of liquid foods on the coating films significantly decreased. This study demonstrates that the Pickering emulsion method is an effective approach for preparing hierarchical wax particles, and that mixing these particles with a polymer similar to the matrix can effectively improve mechanical durability.