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 silanefilled
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.