Mechanistic study of fatigue behavior of vinyltriethoxysilane-coupled carbon black/styrene-butadiene rubber vulcanizate

The increase in fatigue to failure (FTF) cycles by three times was observed for styrene-butadiene rubber (SBR) vulcanizate containing carbon black tre ated with 2.73 phr vinyltriethoxysilane (VTEOS) over the untreated furnace carbon black (UFCB) vulcanizate at an extension ratio of 1.80. There could be several factors responsible for such a phenomenal increases in FTF; howe ver, specifically the chemical reactions associated with this are investiga ted. The UFCB contains carboxylic and lactone groups on its surface besides other groups. On treatment with VTEOS, the ethoxy or silanol group(s) of i t reacts with the carboxylic and lactone groups of UFCB. This provides an i nterface between the particulate UFCB and the flexible rubber matrix unlike UFCB, which adsorbs polymer in absence of VTEOS, Furthermore, the vinyl gr oup thus attached to the UFCB takes part in vulcanization reaction and incr ease in the degree of cross-linking. In addition, the VTEOS substantially r educes the formations of weak polysulphidic linkages. The added flexible in terface increased cross-linking and reduced polysulphidic linkages seem to be mainly responsible to the significant improvement of FTF behavior. (C) 2 000 John Wiley & Sons, Inc.