ROLE OF SALT ON ADHESION OF AN EPOXY/ALUMINUM (OXIDE) INTERFACE IN AQUEOUS ENVIRONMENTS
Kar T. Tan, Christopher C. White, Donald L. Hunston, Justin M. Gorham, Michael Imburgia, Aaron M. Forster, Vogt D. Bryan
Engineering joints consisting of polymer/inorganic interfaces are commonly exposed to less than ideal conditions during normal service; these environmental conditions present a significant challenge for maintaining the structural integrity of the interface. In this contribution, the difference in the debonding behavior of an epoxy/aluminum (oxide) interface when exposed to pure liquid water and aqueous sodium chloride is examined from a mechanistic perspective by using a combination of tools spanning macroscopic adhesion measurement to nanometer-scale probing of water profiles near the buried polymer/substrate interface. In comparison with pure water, the presence of ions in solution can substantially change the crack growth resistance along the interface. For the epoxy-aluminum system examined here, the presence of sodium chloride in the water actually increased the resistance to crack growth. The primary debonding mechanism in this system is controlled by water molecules near the buried interface. From a kinetics prospective, the low diffusive mobilities of hydrated sodium chloride ions can impede interfacial water diffusion, effectively enhancing the interfacial hydrolytic stability. However, the inclusion of the salt also impacts the bulk solubility and interfacial excess by osmotic pressure, so these factors could also influence the long term behavior of the joint. A scaling relationship is adapted to capture quantitatively the role of water molecules and sodium chloride on interfacial debonding.
, White, C.
, Hunston, D.
, Gorham, J.
, Imburgia, M.
, Forster, A.
and Bryan, V.
ROLE OF SALT ON ADHESION OF AN EPOXY/ALUMINUM (OXIDE) INTERFACE IN AQUEOUS ENVIRONMENTS, International Journal of Adhesion and Adhesives, [online], https://doi.org/10.1002/pen.24186
(Accessed December 8, 2023)