Dopamine-Containing Surface Treatments and Adhesives for Structural Bonding of Aluminum
The presence of water generally leads to deterioration in performance of synthetic polymer adhesives, particularly at organic-inorganic interfaces; in addition, water can deteriorate conventional silane coupling agents due to hydrolysis on many metal oxide surfaces. Catechol moieties are well known to be key contributors to the excellent adhesion achieved by mussels in marine environments. We hypothesized that the incorporation of catechol moieties in surface treatments and in the adhesive formulation itself would improve adhesive bonding in moisture-rich environments. To this end, we explored the use of polydopamine-silane hybrid polymers as surface treatments for bonding aluminum with an epoxy resin. Conventional XPS, near-edge X-ray absorption fine structure (NEXAFS), Fourier transform infrared-attenuated total reflectance (FTIR-ATR) infrared spectroscopy and ellipsometry measurements were used to investigate changes in coating composition and thickness, which suggest covalent incorporation of silane into polydopamine. We also explored the direct incorporation of catechol-containing dopamine into the epoxy resin without surface treatments. Single lap shear measurements were conducted to compare these catechol-containing specimens with conventional silane coupling agent surface treatments.
Authors: Ngon T. Tran, Karen J. Gaskell, Joseph L. Lenhart, Joshua A. Orlicki, Daniel A. Fischer, Cherno Jaye, and Daniel B. Knorr, Jr.
Conference: SAMPE Seattle 2017