Adhesive Bonding of Neoprene to Metals in Sonar Devices.

摘要

The mechanisms responsible for debonding of neoprene /steel adhesive bonds during cathodic delamination or during immersion in aqueous solutions of NaOH to simulate the effects of cathodic delamination have been determined. Delamination of the rubber began at the edges of the bonds and proceeded slowly inward. The centers of the bonds were always intact except for very long times when complete delamination of the rubber was observed. Failure was near the primer/oxide interface but islands of rubber remained on the substrate and islands of oxide remained on the rubber. Two failure mechanisms associated with a proprietary primer applied to the substrate prior to bonding were identified. One mechanism was related to oxidative degradation of a phenolic polymer in the primer. The other was related to large osmotic pressures at the bondline resulting from dissolution of zinc chloride. Zinc chloride was formed by reaction of zinc oxide, a component of the primer, with hydrochloric acid evolved from chlorinated rubber, another component of the primer, during curing of the rubber. Debonding of rubber from polished substrates was much faster, leaving little rubber on the substrate failure surfaces and little oxide on the rubber failure surfaces, and indicating that interlocking of the rubber with the substrate has an important effect on the environmental stability of rubber-to-metal bonds. Primers with improved resistance to cathodic delamination were also prepared from epoxy resins. (kt)