Molecular Studies of Adhesion and De-Adhesion on ZnO Nanorod Film-Covered Metals

This paper aims at the investigation of the effect of ZnO nanorod film deposition on the adhesion between a zinc surface and a model epoxy-based adhesive, with and without the adhesion promoter 3-aminopropylphosphonic acid (APPA) treatment. The stability of octadecylphosphonic acid (ODPA) monolayers on ZnO nanorod surfaces was investigated by means of contact angle measurements and FT-IRRAS to simulate wet de-adhesion conditions at the phosphonate-zinc oxide interface. Peel tests were performed under controlled humidity to study the wet de-adhesion of the model epoxy-amine coating from the ZnO nanorod surface. The deposition of ZnO nanorod films resulted in a significant increase of peel forces in comparison with bare zinc. In the case of APPA-treated ZnO nanorod films the increase of the macroscopic adhesion forces was more pronounced. The high surface area ZnO nanorod films provide for the adsorption of polymers as well as adhesion promoters and makes them promising candidates for improving the adhesion properties of engineering metals.