Hydrophobic chitosan/salicylic acid blends film with excellent tensile properties for degradable food packaging plastic materials

Degradable plastic materials made from biopolymer Chitosan (CS) present one of the alternatives to plastic bags for food packaging, but the stability and durability limits its application. Herein, we demonstrated a facile method of producing hydrophobic CS/salicylic acid (SA) film in organic phase for the first time. SA, which can destruct hydrogen bonds of CS was initially blended with CS in N, N-dimethylacetamide using a catalyst. On this basis, CS/SA blend was crosslinked via isocyanate to the hydrophobic CS-SA film. The derivatives structures were characterized using SEM, FTIR, UV-Vis, and fluorescence spectrum. The film-forming ability of CS was maintained, while the hydrophobicity, mechanical strength, and thermal stability of films were improved. These dramatic improvements occurred with the blending effects of CS and SA and the crosslinking effects of organic isocyanate cross linker. The permeabilities to water vapor and water-soluble substances of film were promoted, which are conducive to the application of the film as food packaging. The demonstration of bacteriostatic and grape preservation properties featured the super performance of the synthetic CS/SA film. Our work provides novel food preservation materials, which can replace the commonly used packaging materials and promote the development of the degradable food packaging plastic bags field.