Bonding of Rubber to Carbon Black by Sulfur Vulcanization

Abstract

Abstract As an approach toward understanding the interaction of rubber with carbon black, we have studied the chemisorption of a model olefin (2-methyl-2-octene) on carbon black. Some olefin becomes chemisorbed on simply heating these two materials together, and can be distinguished from physically adsorbed material by its resistance to removal by solvents at room temperature. The presence of an MBTS accelerated sulfur curing system causes additional chemisorption. The amount of olefin chemisorbed can also be increased by the use of larger amounts of sulfur but is decreased by an increase in MBTS, owing to competitive chemisorption of the MBTS. Sulfur is also chemisorbed, to a somewhat greater extent than the olefin, but is desorbed more readily than the olefin, suggesting that these two components are chemisorbed separately. The chemisorbed olefin is believed to be highly mobile on the carbon black surface, and indeed its stability is ascribed primarily to a loss of translational entropy associated with the rate-determining step in desorption. The curing system decreases the stability of the chemisorbed olefin, apparently due to the formation of localized bonds which decrease the translational entropy of the olefin.