The modification of silica particles with phenyltrimethoxysilane or N-[3-(trimethoxysilyl)propyl]aniline
via a solegel reaction was performed in order to improve the dispersion of silica and antidegradation in
natural rubber (NR). The functional groups on the modified silica surface were characterized by Fourier
transform infrared spectroscopy, while the morphology was evaluated by scanning and transmission
electron microscopy. The surface properties and antioxidant activity of the modified silica particles were
determined by the water contact angle and 2, 2-diphenyl-1-picrylhydrazyl assay, respectively. The
modified silica particles exhibited a higher hydrophobicity and a decreased interfacial adhesion energy
compared with the unmodified silica particles. The modified silica particles were then incorporated into
NR. The better dispersion of the modified silica particles than the unmodified ones in the NR matrix
resulted in improved mechanical properties in terms of the modulus at 300% elongation (2.9 ± 0.02 MPa),
hardness (52.5 ± 0.2 Shore A), abrasion resistance (241 ± 8 mm3) and compression set (20.2 ± 0.6%). In
addition, the inclusion of the modified silica particles in the NR matrix gave a high initial temperature of
decomposition and retarded the ozone-induced degradation compared with the NR filled with unmodified
silica particles.