Degradation behavior and aging mechanisms of silicone rubber under Ultraviolet–Thermal–Humidity Coupling in simulated tropical marine atmospheric environment

As a high-performance sealing material widely used in equipment, the degradation behavior and aging mechanism of silicone rubber have garnered significant attention under complex service environments. This study systematically investigates the degradation behavior and aging mechanisms of silicone rubber under simulated Ultraviolet(UV)–Thermal–Humidity (UTH) Coupling conditions in a tropical marine atmospheric environment. By establishing a conversion relationship between laboratory indoor radiation and outdoor UV radiation in the South China Sea, an accelerated aging test was designed. Comprehensive analyses of macroscopic physical properties, mechanical performance, and microstructural evolution reveal distinct phase characteristics of silicone rubber aging under coupling conditions. The early stage is dominated by surface cross-linking and initial oxidation induced by the synergistic effects of UV radiation and humidity. The intermediate stage is characterized by degradation reactions, leading to intensified crack propagation and structural reorganization. The late stage is governed by cross-linking reactions, resulting in densified internal structures. Compared to single-factor UV aging, degradation under coupling conditions penetrates deeper into the material, although the failure modes in both environments similarly transition from early-stage ductile fracture to late-stage brittle fracture. This study elucidates the dynamic relationship between the aging process and environmental factors, providing a theoretical foundation for aging analysis and residual life prediction of silicone rubber under complex coupling conditions. These findings may serve as a useful reference for optimizing the service performance of silicone rubber in marine atmospheric environments.