Effects of layered double hydroxides on poly(vinyl alcohol)/poly(acrylic acid) films for green food packaging applications

Here, a poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA)/layered double hydroxide (LDH) nanocomposite film exhibiting improved gas barrier and mechanical properties was synthesized by incorporating LDH into a PVA/PAA blend film via a relatively facile method. To investigate the effect of the LDH on the nanocomposites, their characteristics, as well as a gas barrier, mechanical, thermal, and optical properties, were evaluated based on their LDH contents (0%, 1%, 2%, 3%, and 5%). The Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) results revealed that LDH could interact with the PVA/PAA matrix. The scanning electron microscopy (SEM) results revealed that the aggregation occurred at an LDH concentration of ≥3%. Further, the barrier and mechanical properties increased up to an LDH content of 2% and decreased at >3%. Particularly, the oxygen permeability decreased by nearly 50%, following the incorporation of the LDH. Moreover, the thermal stability and melting point increased slightly, and the ultraviolet (UV)-blocking properties were improved while the transparency in the visible light region was maintained. These results demonstrated that the most optimal properties were exhibited at an LDH concentration of 2%. The PVA/PAA/LDH nanocomposites were largely nontoxic and ecofriendly; they exhibited high gas barrier and mechanical properties. Therefore, the PVA/PAA/LDH nanocomposite was proposed as a green packaging material with potential applications in the food and medicine fields.