Comparison of reinforcing efficiency between Si-69 and Si-264 in an efficient vulcanization system

Abstract

Silica is the main reinforcing filler for light colored products. Compared with carbon black, the use of silica experiences many problems, particularly poor rubber–filler interaction. In most cases, silane coupling agent is employed to overcome such problems. Since various types of silane coupling agent are now commercially available, the proper selection of silane coupling agent has become an important issue. In the present study, the reinforcing efficiency of bis-(3-triethoxysilylpropyl) tetrasulfane (Si-69) and 3-thiocyanatopropyl triethoxy silane (Si-264) was compared in an efficient vulcanization (EV) system. The results reveal that the addition of silane coupling agents greatly improves the compound processability. The improvement is more pronounced for Si-264. The presence of silane coupling agents also enhances slightly the mechanical properties due to the combined effects of better rubber–filler interaction and better filler dispersion. The optimum loadings of Si-264 and Si-69 are found to be 3.0 and 1.5 phr, respectively. Above such loadings, certain mechanical properties such as tensile and tear strengths are impaired, mainly due to the plasticizing effect for Si-264 and the sulfur contribution effect for Si-69. Compared with Si-264, Si-69 imparts the rubber vulcanizates with better dynamic properties but poorer aging resistance. Again, the explanation is given by the sulfur contribution effect of Si-69.