电缆的安全运行受到多种环境因素的严峻挑战。因此, 为探究复杂环境对电缆护套耐火性能的影响规律, 该研究使用热、盐雾、湿热方法对低烟无卤阻燃电缆护套进行了多因素加速老化处理, 并通过总热释放、极限氧指数、比光密度和残炭量等参数, 分析了多环境因素耦合作用下低烟无卤阻燃电缆护套耐火性能的劣化规律。结果表明：不同的环境因素耦合作用对电缆护套阻燃性能的影响具有显著区别, 其中240 h湿热和120 h盐雾的耦合老化对低烟无卤阻燃电缆护套的耐火性能弱化最为不利, 总热释放增加了8.8%, 极限氧指数降低了6.3%, 最大比光密度增加了124.1%, 800 ℃下的残炭量减小了32.3%。该研究可为服役电缆的维护评估和高性能电缆的设计提供理论基础。

Objective: The fire resistance of cable sheaths, a critical property for safe operation, can be significantly affected by various environmental factors during service. The resultant degradation compromises cable reliability and poses risks to electrical systems and public safety. Low-smoke halogen-free flame-retardant (LSHFR) cable sheaths are widely used for their environmentally friendly and efficient fire-resistant characteristics. However, their long-term performance under complex environmental conditions remains insufficient understood. This study aims to systematically investigate the fire-resistant degradation mechanism of LSHFR under coupled environmental exposures. Methods: To simulate long-term service conditions, multifactor accelerated aging tests were performed using thermal, salt-spray, and hygrothermal treatments. The fire-resistance performance of the cable sheaths was evaluated through cone calorimetry, limiting oxygen index (LOI) testing, thermogravimetric analysis (TGA), smoke density measurement, and contact angle analysis. Key fire-resistance parameters—including total heat release (THR), LOI, specific optical density, and char residue—were compared before and after accelerated aging treatments. Results: Complex environmental conditions markedly weakened the fire resistance of LSHFR cable sheaths. The coupling effects of different environmental factors varied significantly. Among all treatments, the coupled aging of 240 h hygrothermal exposure and 120 h salt-spray exposure (CACS5) produced the most pronounced adverse effects. Compared with unaged samples, this treatment increased THR by 8.8%, decreased LOI by 6.3%, and reduced char residue at 800 ℃ by 32.3%. Smoke suppression performance also deteriorated severely: total smoke production increased by 83.8%, light transmittance decreased by 72.5%, and maximum specific optical density rose by 124.1%. The fire hazards of the cable sheaths intensified with increasing proportions of hygrothermal aging time in the total aging period. Conclusions: This study comprehensively analyzed the degradation mechanisms of the fire resistance of low-smoke halogen-free flame-retardant cable sheaths under complex environmental conditions. The coupled hygrothermal-salt-spray aging treatment had the most detrimental effect on the fire resistance of LSHFR cable sheaths. Deterioration was mainly attributed to the decomposition of key flame-retardant components, reduced thermal stability, and impaired charring ability, leading to increased heat release and smoke production and decreased char residue. The experimental results highlight that exposure to complex environments significantly elevates the fire risk of LSHFR cable sheaths, and the proportion of hygrothermal aging time is a critical factor. These findings offer valuable insights for the development of precise maintenance, evaluation, and design strategies for flame-retardant, and weather-resistant cables with enhanced long-term fire safety.