Abstract <p>Improving the understanding of how recycling and natural additives influence polymer properties is crucial for developing sustainable materials. In this study, we investigated an ethylene–norbornene copolymer (Topas E-140) modified with clove extract, hesperidin, and curcumin through multiple recycling cycles. Differential scanning calorimetry and thermogravimetric analysis, including oxidation induction time measurements, were employed to evaluate changes in thermal stability and structure. The results demonstrate that the polymer’s mechanical integrity is preserved after recycling. The addition of natural additives slightly increases the polymer’s crystallinity (by approximately 20–30%) and shows marginal improvements in thermal stability. These additives also promote a more homogeneous polymer microstructure, as observed by microscopy, and they may enhance the material’s biodegradability. Our findings provide insights into optimizing thermoplastic recycling processes: even low loadings of natural additives can help maintain key material properties. Overall, this study highlights the potential of natural bioadditives to improve the performance and sustainability of recycled polyolefins without significant loss of functionality.</p> Graphical abstract <p></p>