Reactive grafting of 3-octanoylthio-1-propyltriethoxysilane in styrene butadiene rubber: Characterization and its effect on silica reinforced tire composites

A new grafting procedure was established in this present work, where propyltriethoxysilane moiety was successfully grafted in styrene butadiene rubber (SBR) using 3-Octanoylthio-1-propyltriethoxysilane and 2-mercaptobenzothiazole (MBT). Here MBT performed as a better free radical generator for the grafting of silane than peroxide, which is conventionally used. Successful grafting was proved by the Fourier Transform Infrared Spectroscopy (FTIR), where the peak at 1075 cm(-1) was attributed to the presence of Si-O-C group. 9.5 wt percentage of grafting was found for SBR using MBT. On the contrary, with the use of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (Trigonox 101), a high gel content and low amount of grafting (3%) was observed. Grafted structure was confirmed by 2 dimensional Proton Nuclear Magnetic Resonance spectroscopy. The properties of the grafted rubber are also reported here. The glass transition temperature increased and corresponding loss tangent decreased with grafting. In addition, rubber/silica composites were made where silane grafted SBR was used as a compatibilizer. Cure characteristics and other physical properties (Tensile strength, elongation at break, 300% modulus etc.) of the composites were examined. Better dispersion of silica in the grafted rubber matrix was confirmed by various techniques. Dynamic mechanical analysis showed improved rolling resistance and wet grip property indicating its great implications in fire and energy efficient applications.