丙烯酸聚氨酯涂层在我国典型大气环境下的老化历程

本文采用交流阻抗测试技术、傅立叶红外测试技术研究了丙烯酸聚氨酯涂层在我国典型大气环境(武汉、拉萨)下户外降解规律,分析了其降解机理,比较了不同地区的环境老化强度,并探讨了丙烯酸聚氨酯涂层降解过程中电化学等效回路模型的转换问题.结果表明:(i)随曝露时间的延长,涂层的孔隙率增加、孔隙结构增大,体系由一个时间常数特征转为两个时间常数特征,涂层内逐渐形成了腐蚀性离子通往基底金属的通道,基底金属发生腐蚀,随金属腐蚀产物的增加,金属/溶液双电层电容逐渐被具有弥散效应的电容元件替换;(ii)丙烯酸聚氨酯涂层抗蚀性能的降低主要由涂层内高分子链节的断裂所致,随曝露时间的延长,在仲酰胺处发生断裂,生成了新的基团伯酰胺;(iii)丙烯酸聚氨酯涂层在拉萨地区的降解速率较武汉地区快.

Aging Course of Acrylic Polyurethane Coating Exposed in Representative Atmosphere of our country

Outdoor exposure dyna- mic law and corrosion mechanism of acrylic polyurethane coating exposed in representative atmosphere (Wuhan and Lassa) was investigated by EIS and FTIR,environment aging intensity of different zone was Compared,Con- version of EEC during degradation of acrylic polyurethanecoatingwas also discussed.The experimental results were obtained as follows:(i) With the prolongation of exposure timeporosity was increased and pore structure was enlarged in coating.EEC changed accordingly from one-time constant feature to two-time constant feature, accordingly entryway of corrosive ions through coating to metal was formed gradually,metal under the coating was corroded.Accompany increase of corrosion rate of the metal and corro- sion products,metal capacity was not pure capacity but was substituted by differential capacity.(ii) Debasement of corrosion resi sting property of acrylic polyurethane coatingwas due to brokerage of chain.NH was broken and NH_2 was generated with the prol- ongation of aging time.(iii) Compared with Lassa,degradation rate of acry- lic polyurethane coating was smaller in Wuhan.