The cure and tensile properties of sulfur vulcanized styrene-butadiene rubber filled with a conventional furnace black or a fluorinated black have been determined. Compositions with the fluorinated black and normal curative levels exhibit retarded cure compared to corresponding ones with the furnace black. This is due to a reaction between the sulfenamide accelerator and the fluorinated black. Notwithstanding, a fluoro-filled composition with no curatives substantially crosslinks when molded at 150 degrees C. Thus, fluoro-black filled specimens have competing effects toward crosslinking. On the one hand, crosslinking is inhibited by reaction with the accelerator, while, on the other hand, the fluoro-black itself can cause crosslinking.
