环氧云铁与聚氨酯涂层间剥离原因分析

目的剖析沿海某大型工程钢结构环氧云铁与聚氨酯涂层间剥离的原因。方法采用质谱分析仪剖析该聚氨酯涂料的成分,采用离子色谱仪及电导率仪检测所形成聚氨酯氟碳涂膜表面的铵基盐分,环境扫描电镜对剥离涂膜表面观察。结果聚氨酯涂料中含有高沸点溶剂三甲苯、四甲苯,在聚氨酯氟碳复合涂膜与环氧云铁界面之间存在铵基盐物质,通过电镜微观观察发现涂膜固化不完全和微孔存在。结论聚氨酯氟碳涂膜发生可剥离的原因有以下方面,由于聚氨酯涂料中含有高沸点溶剂,挥发时在涂膜中形成微孔;环氧云铁由于低温下环氧固化反应滞缓,与环境中的CO2,H2O反应,生成了氨基甲酸铵盐;氨基甲酸盐在海洋环境下形成水溶物,富集于环氧云铁涂膜和聚氨酯涂膜相粘结的界面处,降低了附着力,从而产生聚氨酯氟碳涂膜严重可剥离现象。

Reason Analysis on Peel-off between Mica Iron Oxide(MIO) Epoxy and Polyurethane Layer

Objective To analyze the reason why polyurethane peels off from epoxy micaceous iron oxide layer in a big coastal steel structure project. Methods The composition of PUFC was analyzed using MS, amino salt on coating surface was detected using ion chromatograph and conductivity meter, and the release coating surface was observed using environmental scanning electron microscope. Results Polyurethane coatings contained high boiling solvents trimethylbenzene and tetramethylbenzene; ammonium salt substance existed on the interface between polyurethane coating and fluorocarbon composite epoxy mica iron oxide; Through the microscopic observation of the electron microscope, the existence of the incomplete and micro pores in the coating was found. Conclusion The causes for peeling off of polyurethane fluorocarbon coating might be explained as the following. Micro pores were formed in the coating because polyurethane coatings contained high boiling solvent. Epoxy mica iron and H2O and CO2 in air reacted to generate carbamate due to the slow curing reaction of epoxy resin at low temperature. Carbamate formed an aqueous solution in marine environment, which was enriched at the adhesive interface of epoxy micaceous iron oxide coating and polyurethane coating, reducing the adhesion and further decreasing the phase interfacial adhesion, leading to severe peelability of polyurethane fluorocarbon coating.