自然浸水-冻融条件下寒区隧道有机保温材料劣化规律研究

为研究聚酚醛、聚氨酯、聚苯乙烯3种寒区隧道有机保温材料的劣化特性，通过室内试验分析自然浸水-冻融条件下材料物理力学性能和微观结构的变化，并基于参数变化对比劣化速率。研究结果表明： 1）各保温材料吸水时均经历快速—平缓—稳定3个阶段。聚酚醛吸水时间最长，为192 h； 50次冻融循环后，聚苯乙烯质量吸水率最高，为67.50%。2）各材料导热系数与冻融循环次数、质量吸水/含冰率的关系采用二元线性模型预测，冻结状态的聚苯乙烯及融化状态的聚氨酯受冻融循环影响最大。3）未冻融时，聚苯乙烯导热系数最低，为0.029 1 W/(m·K)； 但在50次冻融循环之后，融化状态的聚苯乙烯和冻结状态的聚酚醛导热系数最低，分别为0.034 4、0.047 3 W/(m·K)。4）聚氨酯压缩强度远大于其他材料，最高为0.476 MPa。材料隔热性能的劣化主要受微观气泡形态、孔径大小、气孔开裂等因素的影响。

Deterioration Law of Organic Thermal Insulation Materials for Cold Region Tunnels under Natural Water Immersion and Freeze Thaw Conditions

The physico mechanical characteristics and microstructures of the materials are examined based on natural water immersion and freeze thaw cycle by laboratory tests, and the deterioration rates are compared to investigate the deterioration characteristics of organic thermal insulation materials (polyphenolics, polyurethane, and polystyrene). The findings indicate that: (1) The water absorption curves of the thermal insulation materials display three stages of fast, gradual, and stable. The polyphenolics have the longest water absorption duration at 192 h. After 50 freeze thaw cycles, the bulk water absorption rate of polystyrene is the highest, reaching 67.50%. (2) The binary linear model predicts the relationship between thermal conductivity, freeze thaw cycles, and mass water/ice rate for the organic insulation materials. The rigid polystyrene and the thawed polyurethane materials are most vulnerable to freeze thaw cycles. (3) The polystyrene has the lowest thermal conductivity of 0.029 1 W/(m·K) without a freeze thaw cycle. However, after 50 freeze thaw cycles, the thawed polystyrene and rigid polyphenolics exhibit the lowest thermal conductivities, with values of 0.034 4 W/(m·K) and 0.047 3 W/(m·K), respectively. (4) The material with the highest compressive strength, measuring 0.476 MPa is polyurethane. The performance degradation of thermal insulation of materials is mainly affected by the bubble type, pore size, and pore fracture at the microlevel.