Effect of Surface Modification of Calcium Carbonate Nanoparticles by Octyltrimethoxysilane on the Stability of Emulsion and Foam

In this study, the surface modification of calcium carbonate (CaCO3) nanoparticles by a silane coupling agent, octyltrimethoxysilane (OTMS), was investigated and characterized using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) analysis. Both floating tests and contact angle measurements were also conducted to study the effect of OTMS concentration on the hydrophobicity of CaCO3 nanoparticles. It was found that the active ratio for the CaCO3 nanoparticles modified by 1 wt% of OTMS was 97.0 +/- 0.5%, indicating that OTMS is a very effective silane coupling agent in enhancing the hydrophobicity of the CaCO3 nanoparticle surface. The most stable foam was generated with 1 wt% of CaCO3 nanoparticles in aqueous solutions at 1 wt% of OTMS, where the contact angle of water was found to be 91.8 +/- 0.7 degrees. It was also found that the most stable emulsion drops were formed at the same OTMS concentration. These results suggest that CaCO3 nanoparticles modified by a silane coupling agent OTMS are a powerful candidate for a foam stabilizer or an emulsifier in many industrial applications.