In aerospace and military applications as well as many industrial applications, rubber-to-metal bonded parts must exhibit good environmental resistance. Diene rubber vulcanizates contain free double bonds which are sensitive to attack by molecular oxygen and ozone. Natural rubber (NR), polybutadiene (BR), and blends thereof are generally formulated with active antiozonants, both to protect against the degrading effects of environmental ozone and to improve fatigue resistance. The presence of antiozonants in these elastomers has been shown in a previous paper to have an impact on rubber-to-metal adhesion of compounds containing them. This paper continues the investigation into the effect of antiozonant level and type on adhesion of an NR/BR compound to metal. The effect of antiozonants on adhesion is complex and not easily reduced to generalized conclusions. This paper investigates both a conventional high-sulfur cure system and a low-sulfur soluble cure system and includes an evaluation of the environmental robustness of the bond using stressed boiling water testing.
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