Effects of Co-Silanized Silica on the Mechanical Properties and Thermal Characteristics of Natural Rubber/Styrene-Butadiene Rubber Blend

The main aim of this study is to improve the mechanical and thermal stability of the NR/SBR blend using nanosilica. The used nanosilica particles were extracted from hexafluorosilicic acid (H2SiF6) via direct precipitation, using a 20% NH3 solution; after which, they were co-modified with p-tolyltriethoxy silane (PTTES) and bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si-69) silane coupling agents. Many techniques such as the thermal gravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS), were applied to characterize the obtained nanosilica, and to confirm the success of the silanization. The co-modified silica was incorporated into the NR/SBR blend by a conventional two-roll mixing mill and an internal closed mixer, to prepare silica/NR/SBR composites. The morphological, mechanical, rheological, and thermal characteristics of the nanosilica-reinforced NR/SBR rubber blend were also examined in detail. The results indicated that the co-modified silica was an effective reinforcement material for the NR/SBR blend, and that it improved the mechanical properties and thermal stability of the bound rubber. The tensile strength and hardness of the 4 wt.% co-SiO2/NR/SBR composite were higher by 35.23% and 20.12%, respectively, compared with those of the pristine NR/SBR (80/20) blend, in addition to a higher residual char content and decomposition temperature, obtained from thermal degradation.