Abstract:

Fumed silica was surfacely modified with resorcinol and hexamethylenetetramine complex （RH）, and the product was then reacted with natural rubber （NR） to prepare NIL/modified fumed silica （NR/M-silica） nanocomposites via a mixing and curing process. Moreover, the structure and properties of NR/M-silica nano-composites were investigated by mechanical testing, crosslinking density determination, TEM, DSC, FTIR and XPS, and the reinforcement mechanism of M-silica for natural rubber was also discussed. The results show that M-silica has grea- ter reinforcement effect on NR vulcanizate than the common fumed silica, that the comprehensive mechanical properties of NIL/M-silica nano-composite vulcanizates are optimum at a M-silica content of 4% - 10%, that M-silica well disperses in rubber matrix, that both the crosslinking density and the glass transition temperature of the vulcanizate increase, and that, with the addition of modifier RH, there occurs hydrogen bonds between the silicon hydroxyl groups of fumed silica surfaces and the phenol hydroxyl groups of resoreinol formaldehyde resin formed by heating RH, because the characteristic absorption peaks of Si-O bond and silicon hydroxyl group of fumed silica obviously blue-shift and because the binding energy of O atom obviously changes.

Key words: natural rubber, fumed silica, nano-composite, mechanical property, reinforcement mechanism