| "Green Tire" with saving benzine and reducing exhaust emission is believed to be a promising direction of tire industry. Precipitated silica (SiO2) is an especially useful additive to "Green Tire", for reducing rolling resistance, and heat build-up. Howerver, there exist a lot of hydrophilic silanol groups on surfaces of silica, leading to their compatibility with hydrophobic rubbers. Silane having bifunctional group facilitate interaction between SiO2 and rubber which induce more even dispersion due to their compatibilities enhanced.A minimum dump temperature of 130 ℃ is required to ensure silica and silane to react to desired extents. However, at high temperatures, coupling agent such as bis-(3-triethoxysilylpropyl)-tetraslufide (TESPT) either starts to react with rubber or donates sulfur, which leads to scorch. Therefore, requirement of investigation on new silane with lower reactivity during mixing has been fully recognised.3-Hexanoylthio-1-propyltriethoxysilane (HXT) was synthesized from reaction of 3-triethoxysiyl-1-propanethiol and hexanoyl chloride. HXT or bis-(triethoxysilylp-ropyl)-disulfide (TESPD) as coupling agent were incorporated into polymerized styrene-butadiene rubber (SSBR)/silica (SiO2) compounds. Moreover, dynamic rheological behaviors of the compounds were investigated by using an advanced rheomitric expended system (ARES). It is found that incorporation of silane coupling agent into SSBR/SiO2 compounds improves the elastic properties and weaken the "Payne effect" due to the surface modification of SiO2 particles and the improved dispersion of the particles in the SSBR matrix.Effect of silane coupling agent on the dynamic rheological behaviors for unvulcanized SSBR/ SiO2 compounds was also investigated. It is found that the molecular structure of silane coupling agent significantly influences dynamic storage modulus (G') in the temperature region from 100 to 180 ℃ and also the strain (γ) as well as frequency (ω) dependence of G' at 100 ℃. The critical strains (γc) from linearto nonlinear region are 1.00 %, 0.36 % and 0.57 %, and the slopes of plotting logG' vs.logtu in the low co region (terminal region) are 0.14,0.17 and 0.20, for the compounds containing TESPT, TESPD and NXT, respectively. It is suggested that the increase of both yc value and the slopes of those plots are responsible for surface-modification of S1O2 particles and enhancement of interaction between the particle and SSBR.The influence of filler loadings and silane on the dynamic rheological behaviors for unvulcanized SSBR/SiC>2 compounds was investigated. It is found that incorporation of 30 phr SiO2 without silane induces a significant change of the dynamic rheological behaviors for SSBR/SiC>2 compounds because of the strong interactions among SiO2 particales. Meanwhile, it is noted that "Panye effect" and peaks in the high y regions of G' and G" can be observed obviously for SSBR/SiO2 compounds. On the other hands, the influence of different filler loadings with silane on the dynamic rheological behaviors for SSBR/SiC>2 compounds was also investigated. It is found that yc of SSBR/SiC>2 compounds with silane increase and G' and G" peaks in the high y region disappear. The reason for these is resulting from the surface-modification of SiC>2 particles and enhanced interaction between SiC>2 and SSBR.Effect of silane coupling agent on the mechanical properties for vulcanized SSBR/SiC>2 compounds was investigated by a universal testing and dynamic mechanical analysis (DMA). Addition of silica alone leads to significant change in the tensile properties. A remarkable increases in the moduli are observed for SSBR filled with SiO2 containing TESPT. The 100% and 300% moduli of SSBR/SiO2 with silane increase significanty. The ratio of 100% to 300% moduli is reported as an alternative measurement of coupling efficiency. The the highest ratio appears in the vulcanites containing NXT, indicating that the coupling efficiency of NXT is the best. It is also found that the traction properties of SSBR/SiC^ with different silane on water and snow are almost the same and vulcanites containing NXT has the lowest rolling resistance and heat build-up.Keywords: Solution-polymerized styrene butadiene rubber(SSBR), Silica(SiO2), Silane coupling agent, Surface-modification, Dynamic rheological behavior. |
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