Adsorption of silane coupling agents onto kaolinite surfaces

Abstract

AbstractThe adsorption of the silane coupling agents N-(2-amino-ethyl)-3-aminopropyl- trimethoxysilane (Z-6020), N-(2-(vinylbenzyl-amino)-ethyl)-3-amino-propyl-trimethoxysilane (Z-6032) and 3-glycidoxy-propyl-trimethoxysilane (Z-6040) onto the surface of kaolinite has been studied using the solvents water and ethanol. The adsorbed silanes were analysed using diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy and FT-Raman spectroscopy. When the silane coupling agents are dissolved in water, silanol groups are formed. Raman spectra of aqueous solutions of the silanes show that condensation of the silanols into oligomers occurred. The peak at 1000 cm-1 assigned to Si–O–Si vibrations indicates that polymerization has occurred. A similar behaviour is observed when the silanes are dissolved in ethanol. The DRIFT spectra show that the silane coupling agents adsorb onto the surface of kaolinite. It is proposed that the oligomers are bonded to the kaolinite surface only by hydrogen bondings with no covalent bonds formed.