Adhesion at copper- polyamide 11- copper and aluminum-poly amide 11-aluminum laminate interfaces: influence of metal surface oxidation

Abstract

Adhesion at copper-polyamide 11-copper and at aluminum-polyamide 11-aluminum laminate interfaces was studied. Metal-polymer-metal laminates were prepared by compression molding using processing conditions similar to the normal melt processing of polyamide 11. The results show that the time of contact at the molding temperature required to reach a constant level of adhesion is significant. Mild oxidation of the metal prior to molding improves the adhesion of polyamide 11 to aluminum; with copper, a monotonic slow decrease in adhesion with the oxidation time is observed. The presence of a metal surface affects the crystallization behavior of polyamide. With a cooling rate of 40-50°C/min, an approximately 15 µm transcrystalline polymer layer is formed with a degree of crystallinity that is almost 10% higher than the material away from the interface. The metal substrate surface oxidation prior to molding does not change the crystallinity profile of the polymer in the bulk. The polymer surface crystallinity is also a function of the time of contact with the metal substrate. The cooling rate and the metal substrate structure and its nucleating activity are responsible for the surface/bulk crystallinity ratio. Although the highly-crystalline polymer surface layer improves the adhesion to some extent, the formation of active species on the polymer surface which are able to react with the metal surface is mostly responsible for the increase of adhesion with time and its ultimate strength.

Adhesion mechanisms of enamel–varnishes on copper: Adhesion promoter versus corrosion inhibitor

“…The AFM topographic picture presented in Figure 7 shows the peculiar morphology of the oxide layer. Indeed, it was easily removed by gently wiping off the surface with a filter paper, showing the low cohesive nature of the oxide layer 16, 17…”

“…This result confirms the strong influence of temperature on the copper oxidation process, as mentioned before. We then assumed that a nonstable and porous16 copper oxide layer is formed at the copper–enamel interface during thermal aging. This layer is characterized by very low cohesive energy and would lead to a significant drop of the adhesion strength.…”

“…1). These copper–azole complexes seem to act as corrosion inhibitors rather than adhesion promoters 7…”

Polymer-induced metal diffusion during plastic processing: a reason for deposit formation

“…Gundjian and Fisa investigated composite materials made of aluminum-polyamide-aluminum or copper-polyamide-copper [16]. A metal diffusion into the polymer layer could be detected by XPS.…”