Alkylated Lignin/ <scp>HDPE</scp> Composites With Enhanced Photoaging Resistance, Antioxidant Activity, and Mechanical Properties

ABSTRACT High‐density polyethylene (HDPE) undergoes significant degradation and aging during prolonged exposure to ultraviolet radiation and oxidative environments, leading to a pronounced decline in performance. However, developing efficient and sustainable stabilization strategies to enhance the photostability of HDPE remains a major challenge. To address this issue, alkylated lignin (AL) was synthesized via chemical modification as a functional filler to improve compatibility with the nonpolar HDPE matrix, thereby maximizing the intrinsic anti‐aging potential of lignin. The results revealed that at an AL content of 5 wt%, the HDPE‐AL5 composite exhibited optimal tensile strength and elongation at break, even slightly outperforming neat HDPE. Oxidation induction time (OIT) analysis indicated that the OIT of HDPE‐AL5 extended from 32.46 to 50.93 min, significantly outperforming neat HDPE. Ultraviolet – visible spectroscopy confirmed that the HDPE‐AL composites nearly completely provided UV shielding throughout the entire ultraviolet spectrum. After 5 days of irradiation under a xenon lamp, the elongation at break of neat HDPE decreased to 8.77%, whereas HDPE‐AL5 maintained nearly 100% of its original mechanical properties. In summary, the HDPE‐AL5 composite preserves inherent mechanical strength while enhancing UV‐shielding and antioxidant capabilities. This approach offers a promising route for developing sustainable, high‐performance polyethylene materials suitable for outdoor applications.