Synergistic effects of (3-mercaptopropyl)trimethoxysilane and citric acid on the improvement of water vapor barrier performance of polyvinyl alcohol/xylan packaging films

The application of polysaccharide-based films is limited due to core problems, such as poor water vapor barriers and flexibility. From this perspective, silane coupling agents have recently attracted particular interest because of their insensitivity to moisture. However, it may cause poor mechanical properties due to the aggregation of silane coupling agents within the materials. Here, we report a collaborative modification protocol to reduce water vapor transmission capacity and to improve the flexibility of xylan-based films. Xylan from sugarcane bagasse was firstly modified with (3-mercaptopropyl) trimethoxysilane (MPTMS) to obtain MPTMS-modified xylan (MSMX), and then blended with polyvinyl alcohol (PVA) using citric acid (CA) as a cross-linker. The PVA/MSMX/CA films were found to be highly impermeable to water vapor and to have robust solvent resistance. With an optimized mass ratio (PVA/MSMX, 2:1), the water vapor permeability (WVP) value was 2.79 x 10(-13) (g/cm(-1).s .Pa), significantly lower than that of previously reported PVA/xylan-based films. The excellent barrier properties were attributed to the "torturous path effect". Meanwhile, the elongation at break increased up to 480 %, showing a 2-fold enhancement compared to that of PVA/xylan films. This study revealed a great potential of using the PVA/MSMX/CA films as packaging materials for moisture susceptible drugs, food, and electronic components.