Surface Characterization of Methyltrimethoxysilane-Treated Alumina Particles

The compatibility of filler particles with polymer strongly influences composite structure. By altering the surface chemistry of the filler using treating agents such as fatty acids or silane filler–polymer compatibility can be controlled. In this study, we employed a myriad of analytical characterization methods to systematically investigate the surface chemistry of alumina fillers after ex situ treatment with methyltrimethoxysilane (MTM) to confirm the success of treatment. Each technique provides insights from different perspectives and demonstrates that a higher treatment level was achieved as a higher amount of MTM was used, and the resultant treatment formed a uniform layer on the filler surface. Such surface treatment led to a decrease in both dispersive and polar surface energy, which plays a critical role in the control of filler–matrix interactions, and in turn the performance of final products made with such fillers. Despite the use of chemically sensitive spectroscopy tools such as secondary ion mass spectrometry and dynamic nuclear polarization nuclear magnetic resonance, the exact nature of bonding of the treating agent and alumina surface remains elusive without convincing evidence to conclude the formation of the Al–O–Si bond.