• Kontogeorgis, Georgios M.
• Bi, Huichao
• Erik Weinell, Claus
• Dam-Johansen, Kim
• Jhamb, Spardha

Abstract

<p>Waterborneepoxy‑silicone coating formulations are prepared by combining selectedingredients in optimum quantities to produce ~250–275 μm films (dry filmthickness, DFT) applied on polyester, sandblasted steel, smooth steel,acrylic, polypropyleneand aluminum substrates. The self-stratification of the appliedcoatings is then evaluated using Fourier Transform Infrared spectroscopy– Attenuated Total Reflectance (FTIR–ATR) and Scanning ElectronMicroscopy (SEM) with Energy Dispersive X-Ray (EDX) analysis. Thedifference in the absorption spectra of the top and bottom surfaces ofthese films as well as a significant difference in topography seen fromthe SEM images and elemental mapping through an EDX analysis of thecross-section has confirmed the occurrence of stratification onpolyester substrate. The observed stratification results aresubsequently compared with a theoretical model where the primarymechanism driving the separation is assumed to be the surface freeenergy difference of the resins and their respective wetting of thesubstrate. The influence of using two different theories, Wu's HarmonicMean Method and Owens-Wendt Method for the interfacial surface tensionsand the solid surface free energy computations, on the predictions fromthis model is also tested. The theoretical predictions support theobserved results for most cases of the formulated waterborne systems;except for the case of sandblasted steel, the observed results do notmatch the predictions. The possible reasons for the difference inbetween the prediction and observation for this specific case has alsobeen elucidated.</p>

Topics

• impedance spectroscopy
• surface
• scanning electron microscopy
• aluminium
• steel
• density functional theory
• Energy-dispersive X-ray spectroscopy
• resin
• Fourier transform infrared spectroscopy