New designed coupling agents for silica used in green tires with low VOCs and low rolling resistance

Bis-(γ-triethoxysilylpropyl)-tetrasulfide TESPT (Si69) is the most popular silane coupling agent for green tires. However, a large amount of alcohol vapours (a kind of volatile organic compounds (VOCs)) release when it is used for tire production, which can make the process harmful to tire quality and people's health. In this work, M_x-Si69 (x = 1, 2, 3, 4, 5, 6), a series of silane coupling agents were successfully synthesized by transesterification of fatty alcohol polyoxyethylene ether-9 (AEO-9) with Si69. A series of Si69 molecule grafted with one to six fatty alcohol polyoxyethylene ether chains (the long alkoxy chain) (named as M₁-Si69 to M₆-Si69) were produced. The FT-IR and ¹H NMR results revealed that six coupling agents named M₁-Si69 ~ M₆-Si69 could be obtained by adjusting the molar ratio of the reactive monomers. So, the VOCs emission could be reduced by 37.5%~100% theoretically because of the long chain reaction products. The FT-IR and TGA results demonstrated that M_x-Si69 could successfully modify silica. Then, silica/rubber compounds were prepared by adding these low VOCs coupling agents namely M₁-Si69 ~ M₆-Si69. The dynamic and static mechanical results indicated that silica/rubber compound made by adding M₂-Si69 had the lowest Heat-Build up, the best wet skid resistance, and extremely low rolling resistance (it can save more than 20% energy consumption than Si69).