Enhanced weathering performance of epoxy/ZnO nanocomposite coatings via functionalization of ZnO UV blockers with amino and glycidoxy silane coupling agents

This paper aims at improving the weathering performance of an epoxy coating via surface treatment of zinc oxide (ZnO) nanoparticles with different silane coupling agents. The main target of treatment is to suppress the photocatalytic activity of ZnO nanoparticles during weathering exposure. Amino- and glycidoxy-functional silane coupling agents (at three concentration levels) were used for this purpose. The positive influence of such treatment on the weathering performance was approved using different (aesthetic, mechanical, chemical, and topological) techniques. The color change variations results exhibited that ΔE decreased to half (from 6.5 for unfilled to 3.3 for the ZG 1.5-filled coating after 450 h accelerated weathering) in the presence of both modified nanoparticles, especially those treated with glycidoxy silane. FTIR results also approved that carbonyl index, which has increased around 83 % upon weathering for Neat epoxy, varied only 18 % in the presence of glycidoxy-modified ZnO. It was also revealed that modification with the stoichiometric or higher (1.5 stoichiometric) level of silane coupling agents was more effective in such improvement.