Valorization of Agri-Food Waste in Green Composites: Influence of Orange Peel Particulates on Mechanical, Thermal, and Antioxidant PLA Properties

Polymer matrix composites derived from organic waste represent a viable solution for enhancing environmental sustainability. This study investigates the development and characterization of eco-friendly composite filaments using polylactic acid (PLA) reinforced with orange peel particulates (OPPs), evaluating their potential for fused filament fabrication (FFF). PLA/OPP composites were fabricated with varying reinforcement concentrations (2.5–20 wt%) and different particle sizes. The materials were characterized through mechanical testing, thermal analysis (DSC), and FTIR spectroscopy, while functional performance was evaluated via DPPH and ABTS antioxidant assays. The experimental results indicated that a specific low OPP concentration (2.5 wt%) maintained the tensile strength of the neat matrix while significantly improving ductility by 16.67%, thereby enhancing the processability for fused deposition modeling (FDM). Conversely, reinforcement levels exceeding 10 wt% led to a decline in mechanical properties due to fiber agglomeration and matrix saturation. Thermal analysis revealed that higher OPP content influences the crystallization kinetics, while FTIR spectra confirmed good interfacial compatibility through hydrogen bonding. Notably, the incorporation of OPP imparted significant antioxidant activity to the composites, which increased proportionally with filler content. In conclusion, this study demonstrates that low-content PLA/OPP composites successfully balance mechanical performance with functional bioactivity, providing a sustainable material suitable for active packaging and 3D printing applications.