Stabilization of Styrene Pickering Emulsions Using SiO₂ Derived from Waste Cement

The initial focus of this study was placed on the conversion of waste into valuable substances. Waste cement was systematically processed to extract silica powder, which was subsequently functionalized with γ-aminopropyl-trimethoxy-silane (KH550) via covalent grafting. The surface-modified silica particles demonstrated optimized amphiphilicity for interfacial stabilization, as confirmed by contact angle measurements. When employed in styrene/water Pickering emulsions, these modified silica particles exhibited exceptional stabilization efficiency, enabling the synthesis of core–shell polystyrene/silica composite microspheres visualized by SEM. It was demonstrated by the results that the Pickering emulsions could be stabilized by SiO₂ when the appropriate polarity and concentration were achieved. XRD revealed successful silica integration without crystalline phase alteration. Thermogravimetric analysis demonstrated significantly enhanced thermal stability (50.6% residual mass at 800 °C), indicating substantial flame retardancy potential. This waste-to-functional-material strategy not only addresses environmental concerns but also provides an economically viable pathway for advanced polymer composites.