Properties of natural rubber composites reinforced with silica or carbon black: Influence of cure accelerator content and filler dispersion

Filler dispersion is a critical factor in determining the properties of filled rubber composites. Silica has a high density of silanol groups on the surface, which lead to strong filler-filler interactions and a poor filler dispersions. A cure accelerator, N-tert-buty1-2-benzothiazole sulfenamide (TBBS), was found to improve filler dispersion in silica-filled natural rubber (NR) compounds. For the silica-filled NR compounds without the silane coupling agent, the reversion ratio generally increased with increase in TBBS content, whereas those of the silica-filled NR compounds containing the silane coupling agent and carbon black-filled NR compounds decreased linearly. The tensile strength of the silica-filled NR vulcanizate without the silane coupling agent increased as the TBBS content increased, whereas carbon black-filled samples did not show a specific trend. The experimental results were explained by TBBS adsorption on the silica surface and the improvement of silica dispersion with the aid of TBBS.