Mechanism of Rubber-To-Brass Adhesion : Effect of Rubber Composition on the Adhesion

TLDR: In this paper, a new adhesion model for the bonding of sulfur-vulcanizable rubber compounds to brass has been presented and discussed, which is explained on the basis of an autocatalytic effect of a thin film of cuprous sulfide formed on the brass surface by the combined action of sulfur and vulcanization accelerator.

Abstract: A new adhesion model for the bonding of sulfur-vulcanizable rubber compounds to brass has been presented and discussed. The adhesion is explained on the basis of an autocatalytic effect of a thin film of cuprous sulfide formed on the brass surface by the combined action of sulfur and vulcanization accelerator. This film transfers sulfur atoms to rubber molecules, which results in a high rubber surface polarity. This surface bonds to brass by physical interaction. Although minute amounts of cuprous sulfide are a prerequisite, an excess of this compound is detrimental to the adhesion, as thick films are brittle and nonadherent to the brass substrate. Consequently, all parameters which affect the reactivity of a brass surface for cuprous sulfide formation, have an effect on the adhesion. These parameters are brass copper content, brass surface composition, and rubber compound formulation. The action of the various individual rubber ingredients on the reactions at the interface can be simulated by me...