Assessment of the locus of failure of oxygen plasma‐treated rubber/polyurethane adhesive joints using XPS and IRATR spectroscopy

The peel strength of oxygen plasma‐treated rubber/polyurethane adhesive joints was measured as a function of the length of the treatment. The trend obtained did not obey the expected mechanisms of adhesion and therefore the precise determination of the locus of failure of the joints was carried out using XPS and infrared attenuated total reflectance (IRATR) spectroscopy. The oxygen plasma treatment for 1 min facilitated the migration of wax to the surface, which was transferred to the adhesive surface during the curing process. The increase in the length of the treatment up to 20 min produced a change in the locus of failure, which is mixed (adhesional in the oxidized rubber layer and cohesional in the wax layer). The oxygen plasma for 40 min produces a damaged oxidized rubber layer, which acts as a weak layer producing a decrease in peel strength and a cohesive failure in that oxidized layer. Copyright © 2000 John Wiley & Sons, Ltd.