Mechanical Behavior of Plasma-Treated Metal-Rubber Assemblies

Metal-elastomer assemblies, such as aluminum-NBR and stainless steel-FKM, widely used for sealing or damping functions in various fields, are currently prepared with highly toxic bonding agents. To substitute the use of these liquids, plasma technologies were applied. The chemical nature of the plasma polymerized adhesives is found to have no influence on the viscoelastic properties of the elastomer. Furthermore, cohesive assemblies were prepared with acetylene, acrylic acid or maleic anhydride as plasma polymerized layers. Their adhesive performances were evaluated thanks to a tack-like test. Their adhesion mechanisms, even if complex, are namely identified as the interdiffusion of elastomer chains within the plasma-based polymer film and the thermodynamic adhesion. Specifically, we propose that the adhesiveness of metal-rubber assemblies, correlated to the maximum stress at failure in the tack-like test, is proportional to an energy per unit volume. This new variable is determined as the ratio of the surface tension to the thinness of the plasma adhesive.