Chemical and physical interaction between silane coupling agent with long arms and silica and its effect on silica/natural rubber composites

Silica modified by using 3-mercaptopropyl-ethyoxyl-di(tridecyl-pentamethoxy)-silane (Si-747), which is a silane coupling agent with long arms, was investigated in this research. The Si-747 that had a physical interaction with silica (Phy-747) and had a chemical interaction with silica (Che-747) could be separated by the extraction. The amount of Che-747 and Phy-747 were confirmed by thermal gravimetric analyzer (TGA). The effect of Che-747 and Phy-747 on the hydrophilicity of silica were confirmed by Fourier transform infrared (FT-IR). The effect of water on the Phy-747 and the Che-747 were investigated by TGA, FT-IR and X-ray photoelectron spectroscopy (XPS); hydrogen bonds proved to be the main reason for the physical interaction between Si-747 and silica. Both Phy-747 and Che-747 were conducive to the co-coagulation in the preparation of silica/NR masterbatches. The effects of chemical and physical interaction between silica and rubber on different properties of silica/NR composites were also shown in this research.