Surface modification of silica particles and its effects on cure and mechanical properties of the natural rubber composites

The efficiency of modified silica (SiO2) particles in the reinforcement of natural rubber (NR) vulcanizates was evaluated. The SiO2 particles were synthesized via a sol–gel reaction using tetraethyl orthosilicate as the precursor, and then the formed SiO2 particles were modified with methyl, vinyl or aminopropyl groups using methyltriethoxysilane, vinyltriethoxysilane or aminopropyltrimethoxysilane, respectively. Fourier transform infrared spectroscopy and elemental analysis confirmed the successful modification of the surface of the silica particles. The water contact angle measurement revealed the greater hydrophobicity of the three modified silica preparations compared to the unmodified SiO2. NR vulcanizates filled with modified SiO2 particles were prepared and the mechanical, thermal and dynamic mechanical properties of composites were investigated. The morphology of composite materials was also investigated by scanning electron microscopy. The modified SiO2 particles were well dispersed in the NR matrix leading to the good compatibility between the rubber and filler, and so an improved cure, mechanical, thermal and dynamic mechanical properties of the composite vulcanizate materials.