APTES-Functionalized Bentonite for Hierarchical Reinforcement of Gelatin Films: Enhanced Mechanical, Thermal, and Barrier Performance

The growing demand for sustainable, biodegradable food packaging has driven the development of biopolymer films with enhanced functional properties. This study examines the performance of 3-aminopropyl triethoxysilane-modified bentonite (APTES@Bentonite) as a reinforcing nanofiller in gelatin-based films. Bentonite was modified with 10 to 20 wt% APTES through hydrolysis and condensation, which added reactive amine groups and hydrophobic alkyl chains. Adding 3% (w/w) APTES@Bentonite to gelatin films significantly improved their structural, mechanical, thermal, and barrier properties. Scanning electron microscopy showed that 20% APTES functionalization created a uniform clay dispersion with exfoliated layers and no visible aggregation. Fourier transform infrared spectroscopy confirmed the presence of covalent and hydrogen bonds, indicating strong adhesion between the filler and the gelatin matrix. The optimized composite film (20% APTES@Bentonite) showed a 254% increase in tensile strength and a decrease in elongation at break, which corresponds with the formation of a rigid, crosslinked polymer-clay network. Thermal stability improved by 22°C, while water vapor permeability decreased by 33%. Water solubility dropped by 47%, which is due to reduced affinity for water and increased crosslink density. These multiple enhancements result from the combined effects of chemical crosslinking, better compatibility between filler and matrix, hydrophobic surface modification, and a network structure that improves barrier performance. Overall, APTES@Bentonite shows strong potential as a scalable nanofiller for new biodegradable packaging films with high mechanical strength and better moisture resistance.