Interactions of hydrosiloxane and vinylsiloxane groups with aluminum oxide surfaces

Abstract

Silicone‐based materials often contain vinylsiloxane and hydrosiloxane groups for cross‐linking by a radical or addition reaction. Such functional groups can influence the interactions with fillers or with surfaces of substrates when used as adhesives. This work examined how these functional groups interact with aluminum oxide surfaces. For this purpose, aluminum oxide powders with large surface areas of 150 m2/g and different acid‐base properties were examined. Siloxanes were applied as thin layers to mainly obtain information from the interphase by vibrational spectroscopy. It was observed that vinyl groups show low interactions with aluminum oxide surfaces even at elevated temperatures. In contrast to this, hydrosiloxanes undergo strong interactions and reactions with aluminum oxides already at room temperature. Activated Si─H species were observed as an intermediate state. On the one hand, interactions and reactions might contribute to adhesion, but on the other hand, the cross‐linking reaction can be influenced near the surface, leading to lower mechanical strength.