Adsorption of silane coupling agents onto kaolinite surfaces

The adsorption of the silane coupling agents N-(2-amino-ethyl)-3-aminopropy ltrimethoxysilane (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 Four ier transform infrared (DRIFT) spectroscopy and FT-Raman spectroscopy. When the silane coupling agents are dissolved in water, silanol groups are form ed. Raman spectra of aqueous solutions of the silanes show that condensatio n of the silanols into oligomers occurred. The peak at 1000 cm(-1) assigned to Si-O-Si vibrations indicates that polymerization has occurred. A simila r behaviour is observed when the silanes are dissolved in ethanol. The DRIF T spect-ra show that the silane coupling agents adsorb onto the surface of kaolinite, It is proposed that the oligomers are bonded to the kaolinite su rface only by hydrogen bondings with no covalent bonds formed.