Recyclable, hybrid filler/PVA nanocomposite films with enhanced hydrophobic, barrier, UV-resistance and flame-retardant properties for packaging applications

Abstract

Polyvinyl alcohol (PVA) is a biodegradable polymer with outstanding film-forming ability, but its potential applications could be expanded by improving the flammability, hydrophilicity, and barrier properties. To address these challenges, phosphorus-doped carbon dots (PCDs) were embedded into hydrophobically modified porous silica (HPS) to form a multifunctional filler (PCD@HPS), which was incorporated into PVA. The resulting composite films exhibited enhanced flame retardancy, hydrophobicity, and barrier performance. The limiting oxygen index increased from 18.34% for neat PVA to 28.59% with 20 wt% filler concentration, accompanied by self-extinguishing and anti-dripping behaviour. The peak heat release rate for the 20 wt% composite film is 52.87% lower than that for PVA, as indicated by cone calorimetric measurements. Thermogravimetric analysis showed an increase in char yield from 2.9% to 24.3%, with structural analysis (SEM, EDS, FTIR, and XPS) confirming a condensed-phase flame-retardant mechanism through char formation. The water contact angle improved from 38° to 96°, while WVTR and OTR decreased significantly from 230 to 7 g per m² per day and 6 to 0.03 cm³ per m² per day, respectively. The films also demonstrated UV shielding efficiency up to 92%, reduced water absorption, good heat-sealability, antibacterial properties, and recyclability up to 5 repeating cycles with 98% mechanical efficiency. The films evaluated as a packaging material extended the shelf life of strawberries under ambient conditions for 8 days. The study highlights PCD@HPS as an efficient multifunctional additive for developing sustainable, flame-retardant, and barrier-efficient PVA-based active packaging materials.