Preparation and properties of poly (vinyl alcohol)/sodium caseinate blend films crosslinked with glutaraldehyde and glyoxal

Abstract Bio-based films containing poly (vinyl alcohol)/casein have poor mechanical and water vapor barrier properties that limit their use in packaging application. Some properties such as water resistance and tensile strength can be increased by the cross-linking process. For this reason, poly(vinyl alcohol)/sodium caseinate (PVA/SC) blends were crosslinked by adding glutaraldehyde (GLA) and glyoxal (GL) at different ratios in this work. The films were prepared by solution casting technique. Fourier transform infrared analysis (FTIR) confirmed the crosslinking reaction between the components. As a result of the crosslinking, the thicknesses, water vapor barrier properties and water contact angle values of the films have increased. The total soluble matters (TSM) of PVA/SC film decreased with increasing amounts of crosslinkers and GLA crosslinked films exhibited lower TSM. The addition of GLA and GL resulted in more strengthened films as verified by the tensile test. On the other hand, GLA crosslinked films were more flexible than un-crosslinked and GL crosslinked PVA/SC films. The hydrophilic PVA/SC film became more hydrophobic with the increasing amounts of crosslinkers. With the crosslinking, the PVA/SC film became more thermally stable. In conclusion, the crosslinked PVA/SC films were obtained with suitable properties for packaging applications.