Polydopamine and Polydopamine–Silane Hybrid Surface Treatments in Structural Adhesive Applications

Abstract

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.

Synergetic Effect of Dopamine and Alkoxysilanes in Sustainable Non‐Isocyanate Polyurethane Adhesives

“…Dopamine and APTMS can establish covalent interactions contributing to reach shear strength values as high as the TMPTC/MXDA/DOP composition. [ 25,26 ] However, APTMS can accelerate the curing process as reported in our previous work. [ 20 ] In order to confirm this fact, gel times were determined through rheological measurements at 100 °C when crossover between G′ and G″ (tan δ = 1) occurred along the time (Figure S1, Supporting Information).…”

Thermally and light‐triggered reconfigurable shape memory polydopamine/epoxy composite with self‐healing and recyclable ability

“…This results show that the introduction of the PDA plays a positive role in improving the mechanical properties of PDA/sWEP composite. This result is attributed to the characteristics of large specific surface area and rough surface of PDA, and the surface of the PDA particles with large number of functional groups can form hydrogen bonds with the sWEP matrix will improving its mechanical properties 31,37–38 . Moreover, the PDA particles uniformly and independently dispersed between the sWEP molecular chains can absorb more energy to buffer the stress between the molecular chains, thereby increasing the elongation at the break.…”

Enhanced Interfacial and Mechanical Properties of PBX Composites via Surface Modification on Energetic Crystals

“…The surface of the TATB, with a diameter of about 25 μm, displayed some ravines and small holes, which could be caused by different crystallization processes. As can be seen from Figure 2a,b, the surface of PDA-coated TATB exhibited a rougher surface than that of TATB, which was mainly related to the deposition of PDA onto the surface of crystals via particle aggregation [20]. Figure 2c,e,g, as well as their respective inserts, show the surface morphologies of TPG, TPP, and TPE.…”