Glycidyl methacrylate as a non-silane modifier in rubber/silica composites

ABSTRACT Glycidyl methacrylate (GMA) was grafted onto styrene butadiene rubber (SBR) and silica by a solution grafting process. Successful grafting onto rubber and silica was confirmed by Fourier-transform infrared (FTIR) spectrometry, with the peaks at 1149, 842, and 1729 cm−1 attributed to the C–O stretching, the epoxy group, and the C=O stretching vibration of the GMA monomer, respectively. After grafting onto the silica surface, the peak at 842 cm−1 in the spectra disappeared, confirming the grafting reaction through the epoxy group. Grafting onto SBR was also confirmed by proton nuclear magnetic resonance (1H NMR) spectroscopy, and the SBR-GMA interaction was shown using two-dimensional 1H NMR spectroscopy. The grafted products were further characterized by thermogravimetric analysis (TGA) and differencial scanning calorimetry. Grafting density and grafting weight percentage of GMA-grafted silica were calculated using TGA: 10 and 20% GMA-grafted SBR and 20% GMA-grafted silica compounds and their vulcanizates were prepared. Rubber–silica interaction through grafted GMA was shown using FTIR spectroscopy for both types of vulcanizates. Dispersion of pristine and GMA-modified silica onto the SBR matrix was quantified using scanning electron microscopy and atomic force microscopy. Mechanical and dynamic mechanical properties of these GMA-modified vulcanizates were studied and compared with those of previously reported 3-octanoylthio-1-propyltriethoxysilane–modified vulcanizates. The effect of the state of dispersion of silica onto the physico-mechanical properties of the vulcanizates was investigated. The properties of the non-silane–modified systems were comparable with, and in some cases superior to, that of the new mercapto silane-modified systems in the energy-efficient tire application.