Photooxidation of Polyethylene: Chemical Mechanisms and Advanced Characterization Strategies

ABSTRACT Polymeric materials, despite their widespread industrial use, are intrinsically vulnerable to environmental degradation, particularly through photo‐ and thermo‐oxidative processes initiated by solar UV radiation. This article reviews the fundamental mechanisms governing the oxidative aging of polyethylene and examines how these processes control macromolecular deterioration and loss of performance. Emphasis is placed on the role of chromophoric impurities, the radical chain reactions that drive photooxidation, and the competing pathways that differentiate UV‐induced and thermally induced oxidation. The limitations of conventional accelerated aging tests are discussed, highlighting the importance of ensuring mechanistic equivalence between laboratory and natural weathering conditions. A comprehensive overview of analytical methodologies for elucidating the oxidation mechanisms—including infrared spectroscopy, derivatization techniques, fluorescence probing, electron spin resonance, calorimetry, and gas‐phase analysis—is provided, with particular attention to approaches enabling early detection of oxidation and assessment of spatial heterogeneity. Polyethylene serves as a model system to illustrate how molecular‐level transformations, oxidation kinetics, and environmental factors interplay to shape the degradation behavior of polyolefins. The combined mechanistic and analytical perspectives presented here offer a robust basis for improving stabilization strategies and enhancing the predictive reliability of durability assessments for polymeric materials exposed to outdoor environments.