Material PropertiesMechanical and damping properties of silica/natural rubber composites prepared from latex system

In this research, a well-dispersed silica suspension was prepared by using a bead mill before adding into natural rubber (NR) latex for preparing silica/NR masterbatches. The coagulated silica/NR masterbatches with 10-30 parts of silica per hundred parts of rubber (phr) were mixed with other rubber chemicals on a two-roll mill. Cure characteristics, mechanical and damping properties of the vulcanizates prepared from the masterbatches were compared with those prepared by a conventional method. The influence of silane coupling agent, bis-(3-triethoxysilylpropyl) tetrasulfide (Si-69), on the properties of the vulcanizates was also investigated. The results revealed that cure retardation, as typically seen in conventional silica-filled compounds, was not observed for the compounds prepared from silica/NR masterbatches. Without Si-69, the silica/NR masterbatches having more than 10 phr of silica exhibited the greater reinforcement compared to the corresponding conventional mixes. This was attributed to the better silica dispersion in silica/NR masterbatches. Additionally, the masterbatch composite without silane exhibited comparable abrasion resistance, rolling resistance and heat build-up to those of the silane-filled conventional composite when silica loading was less than 30 phr. In the presence of Si-69, the masterbatch composites gave similar damping properties to those of the conventional composites at all silica loadings.