Development of ZnO-Incorporated plasticized PLA nanocomposite films with enhanced physicochemical and antimicrobial properties

Polylactic acid (PLA), a biodegradable aliphatic polyester derived from renewable resources, offers significant potential in sustainable polymer applications but suffers from limited mechanical flexibility and barrier performance. In this study, PLA-based nanocomposite films were developed by incorporating zinc oxide nanoparticles (ZnO NPs) and plasticizers (glycerol or cardanol) to address these limitations. ZnO NPs (200–280 nm) were synthesized via chemical precipitation and characterized using UV–vis spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), dynamic light scattering, X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Field Emission- Scanning Electron Microscopy (FE-SEM). Nanocomposite films containing 1–5 wt% ZnO were fabricated by melt extrusion. Cardanol-plasticized films demonstrated a substantial increase in elongation at break (393.5%) compared to neat PLA (6.17%), while glycerol-plasticized films retained higher tensile strength and modulus. Thermal degradation temperatures decreased with increasing ZnO content, with T_max values shifting from 345 °C (neat PLA) to 315 °C at 5 wt% ZnO, indicating surface-mediated catalytic effects. Barrier testing revealed oxygen permeability (OP) values ranging from 13.9 to 27.8 cm³·mm/m²·day·atm. Additionally, strong antimicrobial activity was observed against Staphylococcus aureus, Aspergillus flavus, and Penicillium commune, and moderate inhibition against Salmonella Typhimurium. The synergistic interplay between ZnO dispersion, plasticizer selection, and matrix morphology resulted in enhanced thermal, mechanical, and antimicrobial properties. These findings demonstrate a promising strategy for tailoring the performance of PLA-based nanocomposites through rational materials design and polymer–nanoparticle interface optimization.