UV ‐Accelerated Aging Behavior of PA66 Fiber Ropes: Molecular Chain Scission Mechanism and Residual Strength Degradation Model

ABSTRACT Polyamide 66 (PA66) fiber ropes are widely employed in harsh outdoor applications, such as marine mooring systems, owing to their high strength and excellent aging resistance. However, long‐term exposure to ultraviolet (UV) radiation induces molecular chain scission in PA66 fibers, resulting in surface morphological degradation, mechanical performance degradation, and a significant reduction in service lifetime. This study presents the first systematic investigation into the multi‐scale evolution mechanism of PA66 ropes under UV aging and develops a residual strength prediction model. The results demonstrate that UV aging induces the formation of microcracks and leads to a 10‐fold increase in surface roughness. Simultaneously, photooxidative chain scission occurs at the molecular level, accompanied by the generation of oxygen‐containing functional groups. Based on the experimental data, a lifetime prediction equation is developed, exhibiting excellent fitting accuracy with a coefficient of determination ( R 2 ) of 0.9971. These findings clarify the UV aging mechanism of PA66 fiber ropes and provide a solid theoretical basis for service life evaluation, preventive maintenance strategies, and the development of high‐weather‐resistance fiber materials for long‐term outdoor applications.