7-Octenyltrimethoxysilane, a model coupling molecule to study the adhesion promotion of a silicone elastomer on an Al 2024 alloy

Ultra-thin layers of 7-octenyltrimethoxysilane (7-OTMS) and of 7-OTMS mixed with n-octyltrimethoxysilane (n-OTMS) (1/1 and 1/10 v/v) have been prepared as adhesion primers for silicone coatings on mechanically polished AA2024 aluminum alloy. The characterization of the silane grafting has been carried out by X-ray photoelectron spectroscopy (XPS), polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS) and water contact angle measurements. Sylgard®184 silicone has been spin-coated and cured on bare and modified aluminum to form 15 μm polymer films. Qualitative peel tests (ASTM D3359) and scanning electron microscopy (SEM) point to the beneficial effect of the 7-OTMS layer to the adhesion whereas mixed layers show comparatively poor adhesion.