不同加速试验对环氧/聚氨酯涂层失效机制的影响

Effects of different accelerated tests on failure process of epoxy/polyurethane coating

研究了模拟南海海洋大气环境下铝合金表面环氧锌黄/丙烯酸聚氨酯涂层体系的失效过程,通过循环加速、紫外/冷凝和中性盐雾的对比试验,探讨了在循环加速试验中紫外-冷凝试验和盐雾试验分别对复合涂层失效过程以及对聚氨酯面漆和环氧底漆失效机制的影响。结果表明,紫外-冷凝过程对丙烯酸聚氨酯面漆有较强的破坏作用,但对复合涂层体系整体的阻抗变化影响较小;紫外-冷凝过程中,位于面漆玻璃化转变温度范围内的试验温度,以及紫外光对氨基甲酸酯基团的破坏作用,是导致面漆发生破坏的主要原因。盐雾试验对面漆的失光率和色差变化影响不大,但连续的盐雾渗透对涂层体系的阻抗下降具有明显的加速作用,同时导致涂层与基材的附着力显著降低。相比单独的紫外-冷凝试验或盐雾试验,循环加速试验综合考虑了南海海洋大气中强太阳辐射、高温高湿、高盐分和温差等环境因素,能更准确反映南海大气环境中复合涂层的失效过程。

Failure process of epoxy zinc yellow primer/acrylic polyurethane coating system on aluminum alloy substrate was studied under simulated ocean atmosphere environment.By comparative evaluation at cyclic acceleration,UV/condensation and neutral salt spray conditions,effects on failure modes of epoxy primer,polyurethane topcoat and composite coating were assessed.Results showed that UV/condensation had strong destructive effect on acrylic polyurethane topcoat,but had little effect on impedance change of overall composite coating.During UV/condensation process,experimental temperature within glass transition temperature of topcoat and UV damage on carbamate group were main reasons for topcoat destruction.Salt spray had minimal effect on change of gloss loss and color difference,whereas consistent salt spray infiltration obviously accelerated impedance decrease of the coating system and caused significant reduction of adhesion between primer and substrate.Compared to UV/condensation or salt spray test alone,cyclic accelerated tests considered influences of different environmental factors such as strong solar radiation,high temperature and humidity,high salinity and temperature difference in ocean atmosphere of the South Sea,which can more accurately reflect failure process of the coating system in the region.