Competition of hydrolysis, self-polymerization and graft coupling for n-dodecyltrimethoxysilane modified Al2O3 under non-catalytic conditions

Silane coupling agent (SCA) modification was a common method to improve the interfacial compatibility between fillers and matrix. In this paper, the competition of silane hydrolysis, self-polymerization and graft coupling during the modification process was investigated under non-homogeneous and non-catalytic conditions from the modification mechanism of SCA. It was found that the degree of hydrolysis, self-polymerization of SCA and graft coupling with Al2O3 surface could be controlled by regulating the reaction conditions and combination of nuclear magnetic resonance hydrogen spectroscopy, thermogravimetric analyzer and X-ray photoelectron spectroscopy is effective methods for measure quantitatively the degree of hydrolysis, self-polymerization of SCA and graft coupling. In addition, free silanes with different degrees of hydrolysis and self-polymerization had obviously influence on the fluidity and store stability of modified spherical Al2O3. Free silanes with smaller degrees of hydrolysis and self-polymerization had lubricating effect and could further reduce the viscosity and with larger degrees of hydrolysis and self-polymerization free products would lead to agglomeration. Therefore, we had a deeper investigation on the modification mechanism for SCA and the role of free silane, which was of guiding significance to control the modification conditions and analyze the stability for modified fillers (agglomeration and long-term storage) in industrial production.