Effect of Zn²⁺ crosslinked semi-interpenetrating network on thermal properties and antibacterial property of hydroxypropyl methylcellulose/sodium alginate blend film

The crosslinked of hydroxypropyl methylcellulose (HPMC) and sodium alginate (SA) with a range of weight ratios formed blend films. Antibacterial packaging films (HPMC/ZA blend film) were prepared by simple ion exchange method with HPMC/SA blend film. The mixture of Zn²⁺ gave a plenty effect of the prepared films. The microstructure, physical properties, structure, and antibacterial properties of crosslinked films were investigated in detail. It was found that the infrared shifted peaks of O–H stretching and O–H bending in crosslinked HPMC/ZA film, which was caused by the formation of hydrogen bond between HPMC and ZA. SEM images of HPMC₅/ZA₅ blend film exhibited rougher structure. In addition, the light transmission, thermal properties, water vapor permeability, and antibacterial activity of HPMC₅/ZA₅ blend film are obviously enhanced, compared with HPMC/SA blend film. Furthermore, HPMC₅/ZA₅ blend film exhibited better antibacterial activity against S. aureus and E. coli, revealing the possible application on food packaging.