Fabrication and properties of novel chitosan/ZnO composite bioplastic

The development of novel biodegradable and ultraviolet (UV) shielding packaging materials has become a research hotspot, which could avoid “white pollution”. Chitosan is an ideal raw material for food packaging but lacks sufficient UV shielding property. In this work, we used an alkali/urea/zincate aqueous solvent to dissolve chitosan, and the resulting chitosan solution was heated with the existence of chemical crosslinker to convert Zn(OH)₄²⁻ into ZnO particles directly. Then, the chitosan/ZnO composite hydrogel sheets were obtained, which were converted to chitosan/ZnO composite bioplastic (CCZP) by a fixing and drying process. The structure and properties of CCZP were investigated with X-ray diffraction (XRD), scanning electron microscopy, XPS, water uptake and tensile testing etc. The results indicated that the in-situ synthesized ZnO particles had distributed evenly in the chitosan matrix. The optical transmittance of the obtained CCZP reached 0.01% at 300 nm and 51.6% at 800 nm, respectively, showing excellent UV shielding performance and relatively good visible light transmittance. Meanwhile, the mechanical properties of the chitosan bioplastic were improved by the incorporation of ZnO, and the tensile strength of CCZP reached up to 49.8 MPa, showing potential application as food packaging materials.