Effect of ZnFe ₂ O ₄ nanoparticles loading on the structural, functional, and degradation behaviour of PLA based nanocomposite films

Biodegradable polymer nanocomposites are being actively explored as sustainable alternatives to conventional plastics for packaging applications. In this study, zinc ferrite (ZF) (ZnFe 2 O 4 ) nanoparticles were synthesized via a sol–gel auto-combustion method and incorporated into polylactic acid (PLA) to fabricate biodegradable nanocomposite films with varying filler contents (0–5 wt%). Structural and morphological analyses confirmed the formation of phase-pure cubic spinel ZnFe 2 O 4 nanoparticles and their effective dispersion within the PLA matrix at lower loadings. The effect of ZnFe 2 O 4 concentration on the mechanical, thermal, barrier, antimicrobial, and soil degradation behaviour of PLA films was systematically investigated. The results revealed a strong concentration-dependent structure–property–degradation relationship. Films containing 2–3 wt% ZnFe 2 O 4 exhibited optimal performance, showing enhanced tensile strength, retained ductility, reduced moisture absorption, effective UV-shielding, and improved antimicrobial activity. In contrast higher filler loadings (4–5 wt%) resulted in nanoparticle agglomeration, leading to reduced mechanical flexibility and delayed biodegradation. This study demonstrates the multifunctional role of ZnFe 2 O 4 as a nanofiller in PLA, enabling simultaneous enhancement of mechanical, barrier, antimicrobial, and degradation properties. The optimized PLA/ZnFe 2 O 4 nanocomposite films (2-3 wt%) offer a balanced combination of functional performance and controlled biodegradability, making them promising candidates for sustainable single-use packaging applications.