1 research outputs found
Polydopamine and Polydopamine–Silane Hybrid Surface Treatments in Structural Adhesive Applications
Numerous studies
have focused on the remarkable adhesive properties
of polydopamine, which can bind to substrates with a wide range of
surface energies, even under aqueous conditions. This behavior suggests
that polydopamine may be an attractive option as a surface treatment
in structural bonding applications, where good bond durability is
required. Here, we assessed polydopamine as a surface treatment for
bonding aluminum plates with an epoxy resin. A model epoxy adhesive
consisting of diglycidyl ether of bisphenol A (DGEBA) and Jeffamine
D230 polyetheramine was employed, and lap shear measurements (ASTM
D1002 10) were made (i) under dry conditions to examine initial bond
strength and (ii) after exposure to hot/wet (63 °C in water for
14 days) conditions to assess bond durability. Surprisingly, our results
showed that polydopamine alone as a surface treatment provided no
benefit beyond that obtained by exposing the substrates to an alkaline
solution of tris buffer used for the deposition of polydopamine. This
implies that polydopamine has a potential Achilles’ heel, namely,
the formation of a weak boundary layer that was identified using X-ray
photoelectron spectroscopy (XPS) of the fractured surfaces. In fact,
for longer deposition times (2.5 and 18 h), the tris buffer-treated
surface outperformed the polydopamine surface treatments, suggesting
that tris buffer plays a unique role in improving adhesive performance
even in the absence of polydopamine. We further showed that the use
of polydopamine–3-aminopropyltriethoxysilane (APTES) hybrid
surface treatments provided significant improvements in bond durability
at extended deposition times relative to both polydopamine and an
untreated control