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-butyl-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. (C) 2003 Society of Chemical Industry.