Sustainable Cross‐Linked PVA/Hard Carbon Composite Films From Rice Husk With Enhanced Antioxidant and Antibacterial Performance

OpenAlex İngilizce

Sustainable utilization of agricultural waste in advanced polymeric materials offers an effective pathway toward environmentally responsible functional systems. In this study, cross‐linked poly(vinyl alcohol) (PVA) composite films reinforced with nitric acid–treated hard carbon (HNO 3 ‐HC) derived from rice husk were successfully fabricated and systematically investigated. Hard carbon was obtained via high‐temperature pyrolysis and subsequently functionalized using nitric acid to improve interfacial compatibility and bioactivity. Composite films containing 1.0, 1.5, and 2.5‐wt% HNO₃‐HC were prepared by solution casting followed by vapor‐phase glutaraldehyde cross‐linking. SEM and EDX analyses confirmed homogeneous dispersion of HNO 3 ‐HC within the PVA matrix, whereas FT‐IR results indicated enhanced hydrogen bonding interactions. Incorporation of HNO 3 ‐HC improved thermal stability, increasing the glass transition temperature from 74.9°C (neat PVA) to 84.3°C for the 2.5‐wt% composite. Water contact angle values decreased from 43.9° to 34.9°, indicating enhanced surface hydrophilicity. Mechanical testing revealed a transition from stiffness‐dominated to ductility‐dominated behavior with increasing filler content, with the highest work at break (1426 N·mm) observed for PVA‐HC‐2.5. Antioxidant activity increased with filler loading, reaching 13.7% (DPPH) and 27.1% (ABTS) inhibition at 60 min for the PVA‐HC‐2.5 sample. Antibacterial assays demonstrated bacterial reduction of up to 72% against Staphylococcus aureus and 65% against Pseudomonas aeruginosa , also observed for PVA‐HC‐2.5. In addition, the lowest water contact angle (34.9°) was recorded for the same formulation. These findings establish rice husk–derived HNO 3 ‐HC as a promising multifunctional biofiller for PVA, enabling the fabrication of sustainable composite films with consistent and measurable enhancements in antioxidant and antibacterial performance relative to pristine PVA.