How APTMS Acts as a Bridge to Enhance the Compatibility of the Interface between the Hydrophilic Poly(vinyl alcohol) Film and the Hydrophobic Stearic Acid Coating

The hydrophobic modification of poly(vinyl alcohol) (PVA) film as a biodegradable packaging material has received significant attention in recent research. Despite the use of stearic acid (SA) as a coating for the PVA film, a challenge persists due to the poor compatibility between SA and PVA. This study addressed the aforementioned issue by utilizing (3-aminopropyl)trimethoxysilane (APTMS) as a bridging agent to establish a connection between the hydrophilic PVA film and the hydrophobic SA coating through hydrogen bonding and chemical reactions. First, SEM and EDS analyses confirmed the enhanced interfacial compatibility between the SA coating and the PVA film. Subsequently, the results from ¹H NMR, FTIR, and XPS experiments presented evidence of hydrogen bonding and chemical reactions among APTMS, SA, and the PVA film. Interestingly, the PVA-APTMS-SA film demonstrated a contact angle of 120.77°, a water absorption of 7.81%, and a water vapor transmission rate of 8.69 g/m²/h. Furthermore, such a composite film displayed exceptional adhesion performance, requiring detachment stresses of 9.86 ± 0.91 and 6.17 ± 0.75 MPa when tested on glass and marble surfaces, respectively. In conclusion, the PVA-APTMS-SA film exhibited significant potential in extending the freshness of fresh-cut apples, making it a promising eco-friendly packaging material for food preservation.