Abstract:Chitosan, a natural macromolecular material, was used as the matrix, and each of four types of hydroxybenzoic acid with different numbers of phenolic hydroxyl groups, that is, salicylic acid (SA), protocatechuic acid (PA), gentisic acid (GTA), and gallic acid (GA), were added to prepare composite films using the solvent casting method. The rheological properties of the composite film solutions were investigated. The structure and properties of the composite films were characterized using thermogravimetry (TG), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The mechanical properties, barrier properties, total phenol release, and oxidation resistance of the composite films were also measured. The results showed a strong interaction between chitosan and hydroxybenzoic acid containing more phenolic hydroxyl groups, leading to a more compact network structure, and thus forming uniform and stable composite films. The composite film based on gallic acid with three phenol hydroxyl groups, which had the best comprehensive performance, exhibited good ultraviolet barrier function, vapor transmission rate of 1.5010-9 g/(m•h•Pa), tensile strength of 23.22 MPa, and DPPH radical scavenging rate of 71.85%. This study showed that the performance of hydroxybenzoic acid and chitosan composite films was influenced by the number of phenolic hydroxyl groups; the higher the number, the better the overall performance of the composite film.
